Benjamin Thompson, like Franklin, was a native of Massachusetts, his ancestors for several generations having been yeomen in that province, and descendants of the first colonists of the Bay. In the diploma of arms granted him when he was knighted by George III., he is described as "son of Benjamin Thompson, late of the province of Massachusetts Bay, in New England, gent." He was born in the house of his grandfather, Ebenezer Thompson, at Woburn, Massachusetts, on March 26, 1753. His father died at the age of twenty-six, on November 7, 1754, leaving the infant Benjamin and his mother to the care of the grandparents. The widow married Josiah Pierce, junior, in March, 1756, and with her child, now a boy of three, went to live in a house but a short distance from her former residence.

Young Thompson appears to have received a sound elementary education at the village school. From some remarks made by him in after years to his friend, M. Pictet, it has been inferred that he did not receive very kind treatment at the hands of his stepfather. It is clear, however, that the most affectionate relationships always obtained between him and his mother, and the latter appears to have had no cause to complain of the treatment she received from her second husband, with whom she lived to a very good old age. That Thompson in early boyhood developed some tendencies which did not meet with ready sympathy from those around him is, however, equally clear. His guardians destined him for a farmer, like his ancestors, and his experiments in mechanics, which took up much of his playtime and in all probability not a few hours which should have been devoted to less interesting work, were not regarded as tending towards the end in view. Hence he was probably looked upon as "indolent, flighty, and unpromising." Later on he was sent to school in Byfield, and in 1764, at the age of eleven, "was put under the tuition of Mr. Hill, an able teacher in Medford, a town adjoining Woburn." At length, his friends having given up all hope of ever making a farmer of the boy, he was apprenticed, on October 14, 1766, to Mr. John Appleton, of Salem, an importer of British goods and dealer in miscellaneous articles. He lived with his master, and seems to have done his work in a manner satisfactory on the whole, but there is evidence that he would, during business hours, occupy his spare moments with mechanical contrivances, which he used to hide under the counter, and even ventured occasionally to practise on his fiddle in the store. He stayed with Mr. Appleton till the autumn of 1769, and during this time he attended the ministry of the Rev. Thomas Barnard. This gentleman seems to have taken great interest in the boy, and to have taught him mathematics, so that at the age of fifteen he was able "to calculate an eclipse," and was delighted when the eclipse commenced within six seconds of his calculated time. Thompson, while an apprentice, showed a great faculty for drawing and designing, and used to carve devices for his friends on the handles of their knives or other implements. It was at this time he constructed an elaborate contrivance to produce perpetual motion, and on one evening it is said that he walked from Salem to Woburn, to show it to Loammi Baldwin, who was nine years older than himself, but his most intimate friend. Like many other devices designed for the same purpose, it had only one fault—it wouldn't go.

It was in 1769, while preparing fireworks for the illumination on the abolition of the Stamp Act, that Thompson was injured by a severe explosion as he was grinding his materials in a mortar. His note-book contained many directions for the manufacture of fireworks.

During Thompson's apprenticeship those questions were agitating the public mind which finally had their outcome in the War of Independence. Mr. Appleton was one of those who signed the agreement refusing to import British goods, and this so affected the trade of the store that he had no further need for the apprentice. Hence it was that, in the autumn of 1769, Thompson went to Boston as apprentice-clerk in a dry goods store, but had to leave after a few months, through the depression in trade consequent on the non-importation agreement.

His note-book, containing the entries made at this time, comprised several comic sketches very well drawn, and a quantity of business memoranda which show that he was very systematic in keeping his accounts. His chief method of earning money, or rather of making up the "Cr." side of his accounts, was by cutting and cording wood. A series of entries made in July and August, 1771, show the expense he incurred in constructing an electrical machine. It is not easy to determine, from the list of items purchased, the character of the machine he constructed; but it is interesting to note that the price in America at that time of nitric acid was 2s. 6d. per ounce; of lacquer, 40s. per pint; of shellac, 5s. per ounce; brass wire, 40s. per pound; and iron wire, 1s. 3d. per yard. The nature of the problems which occupied his thoughts during the last year or two of his business life are apparent in the following letters:—

Woburn, August 16, 1769.

Mr. Loammi Baldwin,
Sir,

Please to inform me in what manner fire operates upon clay to change the colour from the natural colour to red, and from red to black, etc.; and how it operates upon silver to change it to blue.

I am your most humble and obedient servant,

Benjamin Thompson

God save the king.

Woburn, August, 1769.

Mr. Loammi Baldwin,
Sir,

Please to give the nature, essence, beginning of existence, and rise of the wind in general, with the whole theory thereof, so as to be able to answer all questions relative thereto.

Yours,

Benjamin Thompson.

This was an extensive request, and the reply was probably not altogether satisfactory to the inquirer. On the back of the above letter was written:—

Woburn, August 15, 1769.

Sir

There was but few beings (for inhabitants of this world) created before the airy element was; so it has not been transmitted down to us how the Great Creator formed the matter thereof. So I shall leave it till I am asked only the Natural Cause, and why it blows so many ways in so short a time as it does.

Thompson appears now to have given up business and commenced the study of medicine under Dr. Hay, to whom for a year and a half he paid forty shillings per week for his board. During this time he paid part of his expenses by keeping school for a few weeks consecutively at Wilmington and Bradford, and another part was paid by cords of wood. His business capacity, as well as his dislike of ordinary work, is shown by some arrangements which he made for getting wood cut and corded at prices considerably below those at which he was himself paid for it. His note-book made at this time contains, besides business entries, several receipts for medicines and descriptions of surgical operations, in some cases illustrated by sketches. In his work he was methodical and industrious, and the life of a medical student suited his genius far better than that of a clerk in a dry goods store. When teaching at Wilmington he seems to have attracted attention by the gymnastic performances with which he exercised both himself and his pupils. While a student with Dr. Hay, he attended some of the scientific lectures at Harvard College. The pleasure and profit which he derived from these lectures are sufficiently indicated by the fact that forty years afterwards he made the college his residuary legatee.

Thompson won such a reputation as a teacher during the few weeks that he taught in village schools in the course of his student life, that he received an invitation from Colonel Timothy Walker to come to Concord, in New Hampshire, on the Merrimack, and accept a permanent situation in a higher grade school. It was from this place that he afterwards took his title, for the early name of Concord was Rumford, and the name was changed to Concord "to mark the restoration of harmony after a long period of agitation as to its provincial jurisdiction and its relation with its neighbours."

The young schoolmaster of Concord was soon on very intimate terms with the minister of the town, the Rev. Timothy Walker,[5] a man who was so much respected that he had thrice been sent to Britain on diplomatic business. Mr. Walker's daughter had been married to Colonel Rolfe, a man of wealth and position, and, with the exception of the Governor of Portsmouth, said to have been the first man in New Hampshire to drive a curricle and pair of horses. Thompson soon married—or, as he told Pictet, was married to—the young widow. Whatever may have been implied by this other way of putting the question, there is no doubt that Thompson always had the greatest possible respect for his father-in-law, and ever remembered him with sincere gratitude. The fortunes of the gallant young schoolmaster now appeared to be made; when the engagement was settled, the carriage and pair were brought out again, and the youth was attired in his favourite scarlet as a man of wealth and position. In this garb he drove to Woburn, and introduced his future wife to his mother, whose surprise can be better imagined than described.

The exact date of Thompson's marriage is not known. His daughter Sarah, afterwards Countess of Rumford, was born in the Rolfe mansion on October 18, 1774. It is needless to say that the engagement to Mrs. Rolfe terminated the teaching at the school.

Thompson now had a large estate and ample means to improve it. He gave much attention to gardening, and sent to England for garden seeds. In some way he attracted the attention of Governor Wentworth, the Governor of Portsmouth, who invited him to the Government House, and was so taken with the former apprentice, medical student, and schoolmaster, that he gave him at once a commission as major. This appointment was the cause of the misfortunes which almost immediately began to overtake him. He incurred the jealousy of his fellow-officers, over whom he had been appointed, and he failed to secure the confidence of the civilians of Concord.

Public feeling in New England was very much excited against the mother country. Representations were sent to the British Government, but appeared to be treated with contempt. Very many of these documents were found, after the war was over, unopened in drawers at the Colonial Office. British ministers appeared to know little about the needs of their American dependencies, and relations rapidly became more and more strained. The patriots appointed committees to watch over the patriotism of their fellow-townsmen, and thus the freedom of a free country was inaugurated by an institution bordering in character very closely upon the Inquisition; and the Committees of Correspondence and Safety accepted evidence from every spy or eavesdropper who came before them with reports of suspected persons. Thompson was accused of "Toryism;" the only definite charge against him being that he had secured remission of punishment for some deserters from Boston who had for some time worked upon his estate. He was summoned before the Committee of Safety, but refused to make any confession of acts injurious to his country, on the ground that he had nothing to confess. His whole after-life shows that his sympathies were very much on the side of monarchy and centralization, but at this time there appears to have been no evidence that could be brought against him. The populace, however, stormed his house, and he owed his safety to the fact that he had received notice of their intentions, and had made his escape a few hours before. This was in November, 1774. Thompson then took refuge at Woburn, with his mother, but the popular ill feeling troubled him here, so that his life was one of great anxiety.

While at Woburn, his wife and child joined him, and stayed there for some months. At length he was arrested and confined in the town upon suspicion of being inimical to the interests of his country. When he was brought before the Committee of Inquiry, there was no evidence brought against him. Major Thompson then petitioned to be heard before the Committee of the Provincial Congress at Washington. This petition he entrusted to his friend Colonel Baldwin to present. The petition was referred by the committee to Congress, by whom it was deferred for the sake of more pressing business. At length he secured a hearing in his native town, but the result was indecisive, and he did not obtain the public acquittal that he desired, though the Committee of Correspondence found that the "said Thompson" had not "in any one instance shown a disposition unfriendly to American liberty; but that his general behaviour has evinced the direct contrary; and as he has now given us the strongest assurances of his good intentions, we recommend him to the friendship, confidence, and protection of all good people in this and the neighbouring provinces." This decision, however, does not appear to have been made public; and Thompson, on his release, retired to Charlestown, near Boston. When the buildings of Harvard College were converted into barracks, Major Thompson assisted in the transfer of the books to Concord. It is said that, after the battle of Charlestown, Thompson was introduced to General Washington, and would probably have received a commission under him but for the opposition of some of the New Hampshire officers. He afterwards took refuge in Boston, and it does not appear that he ever again saw his wife or her father. His daughter he did not see again till 1796, when she was twenty-two years of age. On March 24, 1776, General Washington obliged the British troops to evacuate Boston; Thompson was the first official bearer of this intelligence to London. Of course, his property at Concord was confiscated to the commonwealth of Massachusetts, and he himself was proscribed in the Alienation Act of New Hampshire, in 1778.

When Thompson reached London with the intelligence of the evacuation of Boston, Lord George Germaine, the Secretary for War, saw that he could afford much information which would be of value to the Government. An appointment was soon found for him in the Colonial Office, and afterwards he was made Secretary of the Province of Georgia, in which latter capacity, however, he had no duties to fulfil. Throughout his career in the Colonial Office he remained on very intimate terms with Lord George Germaine, and generally breakfasted with him. In July, 1778, he was guest of Lord George at Stoneland Lodge, and here, in company with Mr. Ball, the Rector of Withyham, he undertook experiments "to determine the most advantageous situation for the vent in firearms, and to measure the velocities of bullets and the recoil under various circumstances."

The results of these investigations procured for him the friendship of Sir Joseph Banks, the President of the Royal Society, and Thompson was not the man to lose opportunities for want of making use of them. In 1779 he was elected a Fellow of the Royal Society, "as a gentleman well versed in natural knowledge and many branches of polite learning." In the same year he went for a cruise in the Victory with Sir Charles Hardy, in order to pursue his experiments on gunpowder with heavy guns. Here he studied the principles of naval artillery, and devised a new code of marine signals. In 1780 he was made Under-Secretary of State for the Northern Department, and in that capacity had the oversight of the transport and commissariat arrangements for the British forces.

On the defeat of Cornwallis, Lord George Germaine and his department had to bear the brunt of Parliamentary dissatisfaction. Lord George resigned his position in the Government, and was created Viscount Sackville. He had, however, previously conferred on Thompson a commission as lieutenant-colonel in the British army, and Thompson, probably foreseeing the outcome of events and its effect on the Ministry, was already in America when Lord George resigned. He had intended landing at New York, but contrary winds drove him to Charlestown. It is needless to trace the sad events which preceded the end of the war. It was to be expected that many bitter statements would be made by his countrymen respecting Thompson's own actions as colonel commanding a British garrison, for at length he succeeded in reaching Long Island, and taking the command of the King's American Dragoons, who were there awaiting him. The spirit of war always acts injuriously on those exposed to its influence, and Lieutenant-Colonel Thompson in Long Island was doubtless a very different man from that which we find him to have been before and after; nor were the months so spent very fruitful in scientific work.

In 1783, before the final disbanding of the British forces, Thompson returned to England, and was promoted to the rank of colonel, with half-pay for the rest of his life. Still anxious for military service, he obtained permission to travel on the Continent, in hopes of serving in the Austrian army against the Turks. He took with him three English horses, which rendered themselves very objectionable to his fellow-travellers while crossing the Channel in a small boat. Thompson went to Strasbourg, where he attracted the attention of the Prince Maximilian, then Field-Marshal of France, but afterwards Elector of Bavaria. On leaving Strasbourg, the prince gave him an introduction to his uncle, the Elector of Bavaria. He stayed some days at Munich, but on reaching Vienna learned that the war against the Turks would not be carried on, so he returned to Munich, and thence to England.

M. Pictet gives the following as Rumford's account of the manner in which he was cured of his passion for war:—

"'I owe it,' said he to me, one day, 'to a beneficent Deity, that I was cured in season of this martial folly. I met, at the house of the Prince de Kaunitz, a lady, aged seventy years, of infinite spirit and full of information. She was the wife of General Bourghausen. The emperor, Joseph II., came often to pass the evening with her. This excellent person conceived a regard for me; she gave me the wisest advice, made my ideas take a new direction, and opened my eyes to other kinds of glory than that of victory in battle.'"

If the course in life which Colonel Thompson afterwards took was due to the advice of this lady, she deserves a European reputation. The Elector of Bavaria, Charles Theodore, gave Thompson a pressing invitation to enter his service in a sort of semi-military and semi-civil capacity, to assist in reorganizing his dominions and removing the abuses which had crept in. Before accepting this appointment, it was necessary to obtain the permission of George III. The king not only approved of the arrangement, but on February 23, 1784, conferred on the colonel the honour of knighthood. Sir Benjamin then returned to Bavaria, and was appointed by the elector colonel of a regiment of cavalry and general aide-de-camp. A palatial residence in Munich was furnished for him, and here he lived more as a prince than a soldier. It was eleven years before he returned, even on a visit, to England, and these years were spent by him in works of philanthropy and statesmanship, to which it is difficult to find a parallel. At one time he is found reorganizing the military system of the country, arranging a complete system of military police, erecting arsenals at Mannheim and Munich; at another time he is carrying out scientific investigations in one of these arsenals; and then he is cooking cheap dinners for the poor of the country.

One great evil of a standing army is the idleness which it develops in its members, unfitting them for the business of life when their military service is ended. Thompson commenced by attacking this evil. In 1788 he was made major-general of cavalry and Privy Councillor of State, and was put at the head of the War Department, with instructions to carry out any schemes which he had developed for the reform of the army and the removal of mendicity. Four years after his arrival in Munich he began to put some of his plans into operation. The pay of the soldiers was only threepence per day, and their quarters extremely uncomfortable, while their drill and discipline were unnecessarily irksome. Thompson set to work to make "soldiers citizens and citizens soldiers." The soldier's pay, uniform, and quarters were improved; the discipline rendered less irksome; and schools in which the three R's were taught were connected with all the regiments,—and here not only the soldiers, but their children as well as other children, were taught gratuitously. Not only were the soldiers employed in public works, and thus accustomed to habits of industry, while they were enlivened in their work by the strains of their own military bands, but they were supplied with raw material of various kinds, and allowed, when not on duty, to manufacture various articles and sell them for their own benefit—an arrangement which in this country to-day would probably raise a storm of opposition from the various trades. The garrisons were made permanent, so that soldiers might all be near their homes and remain there, and in time of peace only a small portion of the force was required to be in garrison at any time, so that the great part of his life was spent by each soldier at home. Each soldier had a small garden appropriated to his use, and its produce was his sole property. Garden seeds, and especially seed potatoes, were provided for the men, for at that time the potato was almost unknown in Bavaria. Under these circumstances a reform was quickly effected; idle men began to take interest in their gardens, and all looked on Sir Benjamin as a benefactor.

Having thus secured the co-operation of the army, Thompson determined to attack the mendicants. The number of beggars may be estimated from the fact that in Munich, with a population of sixty thousand, no less than two thousand six hundred beggars were seized in a week. In the towns, they possessed a complete organization, and positions of advantage were assigned in regular order, or inherited according to definite customs. In the country, farm labourers begged of travellers, and children were brought up to beggary from their infancy. Of course, the evils did not cease with simple begging. Children were stolen and ill treated, for the purpose of assisting in enlisting sympathy, and the people had come to regard these evils as inevitable. Thompson organized a regular system of military patrol through every village of the country, four regiments of cavalry being set apart for this work. Then on January 1, 1790, when the beggars were out in full force to keep their annual holiday, Thompson, with the other field officers and the magistrates of the city, gave the signal, and all the beggars in Munich were seized upon by the three regiments of infantry then in garrison. The beggars were taken to the town hall, and their names and addresses entered on lists prepared for the purpose. They were ordered to present themselves next day at the "military workhouse," and a committee was appointed to inquire into the condition of each, the city being divided into sixteen districts for that purpose. Relieved of an evil which they had regarded as inevitable, the townspeople readily subscribed for the purpose of affording systematic relief, while tradesmen sent articles of food and other requisites to "the relief committee." In the military workhouse the former mendicants made all the uniforms for the troops, besides a great deal of clothes for sale in Bavaria and other countries. Thompson himself fitted up and superintended the kitchen, where food was daily cooked for between a thousand and fifteen hundred persons; and, under Sir Benjamin's management, a dinner for a thousand was cooked at a cost for fuel of fourpence halfpenny—a result which has scarcely been surpassed in modern times, even at Gateshead.

That Thompson's work was appreciated by those in whose interest it was undertaken is shown by the fact that when, on one occasion, he was dangerously ill, the poor of Munich went in public procession to the cathedral to pray for him, though he was a foreigner and a Protestant. Perhaps it may appear that his philanthropic work has little to do with physical science; but with Thompson everything was a scientific experiment, conducted in a truly scientific manner. For example, the lighting of the military workhouse afforded matter for a long series of experiments, described in his papers on photometry, coloured shadows, etc. The investigations on the best methods of employing fuel for culinary purposes led to some of his most elaborate essays; and his essay on food was welcomed alike in London and Bavaria at a time of great scarcity, and when famine seemed impending.

The Emperor Joseph was succeeded by Leopold II., but during the interregnum the Elector of Bavaria was Vicar of the Empire, and he employed the power thus temporarily placed in his hands in raising Sir Benjamin to the dignity of Count of the Holy Roman Empire, with the order of the White Eagle, and the title which the new count selected was the old name of the village in New England where he had spent the two or three years of his wedded life.

In 1795 Count Rumford returned to England, in order to publish his essays, and to make known in this country something of the work in which he had been engaged. Soon after his arrival he was robbed of most of his manuscripts, the trunk containing them being stolen from his carriage in St. Paul's Churchyard. On the invitation of Lord Pelham, he visited Dublin, and carried out some of his improvements in the hospitals and other institutions of that city. On his return to London he fitted up the kitchen of the Foundling Hospital.

Lady Thompson lived to hear of her husband's high position in Bavaria, but died on January 29, 1792. When Rumford came to London in 1795, he wrote to his daughter, who was then twenty-one years of age, to meet him there, and on January 29, 1796, she started in the Charlestown, from Boston. She remained with her father for more than three years, and her autobiography gives much information respecting the count's doings during this time.

While in London, Count Rumford attained a high reputation as a curer of smoky chimneys. One firm of builders found full employment in carrying out work in accordance with his instructions; and in his hotel at Pall Mall he conducted experiments on fireplaces. He concluded that the sides of a fireplace ought to make an angle of 135° with the back, so as to throw the heat straight to the front; and that the width of the back should be one-third of that of the front opening, and be carried up perpendicularly till it joins the breast. The "Rumford roaster" gained a reputation not less than that earned by his open fireplace.

It was during this stay in London that Rumford presented to the Royal Society of London, and to the American Academy of Sciences £1000 Three per Cent. Stock, for the purpose of endowing a medal to be called the Rumford Medal, and to be given each alternate year for the best work done during the preceding two years in the subjects of heat and light. He directed that two medals, one in gold and the other in silver, should be struck from the same die, the value of the two together to amount to £60. Whenever no award was made, the interest was to be added to the principal, and the excess of the income for two years over £60 was to be presented in cash to the recipient of the medal. At present the amount thus presented is sufficient to pay the composition fee for life membership of the Royal Society. The first award of the medal was made in 1802, to Rumford himself. The other recipients have been John Leslie, William Murdock, Étienne-Louis Malus, William Charles Wells, Humphry Davy, David Brewster, Augustin Jean Fresnel, Macedonio Melloni, James David Forbes, Jean Baptiste Biot, Henry Fox Talbot, Michael Faraday, M. Regnault, F. J. D. Arago, George Gabriel Stokes, Neil Arnott, M. Pasteur, M. Jamin, James Clerk Maxwell, Kirchoff, John Tyndall, A. H. L. Fizeau, Balfour Stewart, A. O. des Cloiseaux, A. J. ÅngstrÖm, J. Norman Lockyer, P. J. C. Janssen, W. Huggins, Captain Abney.

In the summer of 1796 Rumford and his daughter left England to return to Munich. On account of the war, they were obliged to go by sea to Hamburg; whence they drove to Munich, where the count was anxiously expected, political troubles having compelled the elector to leave the city. After the battle of Friedburg, the Austrians retired to Munich, and, finding the gates of the city closed, they fortified themselves on an eminence overlooking the city, and, through some misunderstanding with the local authorities, the Austrian general threatened to attack the city if any Frenchman should be allowed to enter. Rumford took supreme command of the Bavarian forces, and so gained the respect of the rival generals that neither the French nor the Austrians made any attempt to enter the city. The large number of soldiers now in Munich gave Rumford a good opportunity to exercise his skill in cooking on a large scale, and this he did, adding to the comfort of the soldiers and reducing the cost of the commissariat. On the return of the elector, Miss Sarah was made a countess, and one-half of her father's pension was secured to her, thus providing her with an income of about £200 per annum for life. Many of the details of the home life and social intercourse during this period of residence at Munich are preserved in the autobiography of the countess, as well as accounts of excursions, including a trip by river to Salzburg for the purpose of inspecting the salt-mines. After two years' stay in Munich, the count was appointed Minister Plenipotentiary from Bavaria to the Court of Great Britain. After an unpleasant and perilous journey, he reached London, vi Hamburg, in September, 1798, but was terribly disappointed on learning that a British subject could not be accepted as an envoy from a Foreign Power. As he did not then wish to return to Bavaria, he purchased a house in Brompton Row. But he had been too much accustomed to great enterprises to be content with a quiet life, and was bound to have some important scheme on hand. Pressing invitations were sent him to return to America, but he preferred residence in London, and devoted himself to the foundation of the Royal Institution, though the countess returned to the States in August, 1799. A letter from Colonel Baldwin to her father shortly after her return contains the following passage:—

In the cask of fruit which your daughter and Mr. Rolfe have sent you, there is half a dozen apples of the growth of my farm, wrapped up in papers, with the name of Baldwin's apples written upon them.... It is (I believe) a spontaneous production of this country; that is, it was not originally engrafted fruit.

The history of the remaining period of Rumford's residence in London is the early history of the Royal Institution.

For many years Rumford had had at his disposal for his philanthropic projects all the resources of the electorate of Bavaria, and he had done everything on a royal scale. His original plan for the Royal Institution appears to embody to a very great extent the work of the Science and Art Department, the City and Guilds Institute for the Advancement of Technical Education, the National School of Cookery, the London Society for the Extension of University Teaching, and, in addition to all this, to have comprehended a sort of perpetual International Health Exhibition, where every device for domestic purposes, and especially for the improvement of the condition of the poor, could be inspected. How all this was to be carried out with the resources which the count expected to be able to devote to the purpose, does not appear. Foremost among the objects of the institution was placed the management of fire; for its promoter was convinced that more than half the fuel consumed in the country might be saved by proper arrangements.

The philanthropic objects with which the institution was started are apparent from the fact that it was the Society for Bettering the Condition of the Poor which appointed a committee to confer with Rumford, to report on the scheme, and to raise the funds necessary for starting the project; and one of Rumford's hopes in connection with it was "to make benevolence fashionable." It was arranged that donors of fifty guineas each should be perpetual proprietors of the institution; and that subscribers should be admitted at a subscription of two guineas per annum, or ten guineas for life. The price of a proprietor's share was raised to sixty guineas from May 1, 1800, and afterwards increased by ten guineas per annum up to one hundred guineas. In a very short time there were fifty-eight fifty-guinea subscribers, and to them Rumford addressed a pamphlet, setting forth his scheme in detail. The following are specified as some of the contents of the future institution:—"Cottage fireplaces and kitchen utensils for cottagers; a farm-house kitchen with its furnishings; a complete kitchen, with its utensils, for the house of a gentleman of fortune; a laundry, including boilers, washing, ironing, and drying rooms, for a gentleman's house, or for a public hospital; the most improved German, Swedish, and Russian stoves for heating rooms and passages." As far as possible all these things were to be seen at work. There were also to be ornamental open stoves with fires in them; working models of steam-engines, of brewers' boilers, of distillers' coppers and condensers, of large boilers for hospital kitchens, and of ships' coppers with the requisite utensils; models of ventilating apparatus, spinning-wheels and looms "adapted to the circumstances of the poor;" models of agricultural machinery and bridges, and "of all such other machines and useful instruments as the managers of the institution shall deem worthy of public notice." All articles were to be provided with proper descriptions, with the name and address of the maker, and the price.

A lecture-room and laboratory were to be fitted up with all necessary philosophical apparatus, and the most eminent expounders of science were to be engaged for the purpose of "teaching the application of science to the useful purposes of life."

The lectures were to include warming and ventilation, the preservation of food, agricultural chemistry, the chemistry of digestion, of tanning, of bleaching and dyeing, "and, in general, of all the mechanical arts as they apply to the various branches of manufacture." The institution was to be governed by nine managers, of whom three were to be elected each year by the proprietors; and there was also to be a committee of visitors, the members of which should not be the managers. The king became patron of the institution, and the first set of officers was nominated by him. The Earl of Winchelsea and Nottingham was President; the Earls of Morton and of Egremont and Sir Joseph Banks, Vice-Presidents; the Earls of Bessborough, of Egremont, and of Morton, and Count Rumford, were among the Managers; the Duke of Bridgewater, Viscount Palmerston, and Earl Spencer the Visitors; and Dr. Thomas Garnett was appointed first Professor of Physics and Chemistry. The royal charter of the institution was sealed on January 13, 1800. The superintendence of the journals of the institution was entrusted to Rumford's care. For some time the count resided in the house in Albemarle Street, which had been purchased by the institution, and while there he superintended the workmen and servants.

Dr. Thomas Garnett, the first professor at the institution, was highly respected both as a man and a philosopher, and seems to have been everywhere well spoken of. But Rumford and he could not work together, and his connection with the institution was consequently a short one. Rumford was then authorized to engage Dr. Young as Professor of Natural Philosophy, editor of the journals, and general superintendent of the house, at a salary of £300 per annum. Shortly before this the count's attention had been directed to the experiments on heat, made by Humphry Davy, and on February 16, 1801, it was "resolved that Mr. Humphry Davy be engaged in the service of the Royal Institution, in the capacity of Assistant-Lecturer in Chemistry, Director of the Chemical Laboratory, and Assistant-Editor of the Journals of the Institution; and that he be allowed to occupy a room in the house, and be furnished with coals and candles, and that he be paid a salary of one hundred guineas per annum." In his personal appearance, Davy is said to have been at first somewhat uncouth, and the count was by no means charmed with him at their first interview. It was not till he had heard him lecture in private that Rumford would allow Davy to lecture in the theatre of the institution; but he afterwards showed his complete confidence in the young chemist by ordering that all the resources of the institution should be at his service. Davy dined with Rumford at the count's house in Auteuil, when he visited Paris with Lady Davy and Faraday, in 1813. He commenced his duties at the institution on March 11, 1801. It was on June 15, in the same year, that the managers having objected to the syllabus of his lectures, Dr. Garnett's resignation was accepted; and on July 6 Dr. Young was appointed in his stead. Dr. Young resigned after holding the appointment only two years, as he found the duties incompatible with his work as a physician.

Rumford's life in London now became daily more unpleasant to himself. Accustomed, as he had been in Bavaria, to carry out all his projects "like an emperor," it was difficult for him to work as one member of a body of managers. One by one he quarrelled with his colleagues, and at length left England, in May, 1802, never to return.

When distinguished men of science are placed at the head of an institution like that which Rumford founded, there is always a tendency for the technical teaching of the establishment to become gradually merged into scientific research; and in this case, after Rumford's departure, the genius of Davy gradually converted the Royal Institution into the establishment for scientific research which it has been for more than three quarters of a century. Probably the man who has come nearest to realizing all that Count Rumford had planned for his institution is the late Sir Henry Cole; but he succeeded only through the resources of the Treasury.

On leaving England in May, 1802, Rumford went to Paris, where he stayed till July or August, when he revisited Bavaria and remained there till the following year, when he returned to Paris. He was again at Munich in 1805; but under the new elector, though an old friend of the count, relationships do not seem to have been all that they were with his uncle, and at length the elector himself was compelled to leave Munich, and soon after the Bavarian sovereign became a vassal of Napoleon. On October 24, 1805, Rumford married Madame Lavoisier, a lady of brilliant talents and ample fortune. That his position might be nearly equal to hers, the Elector of Bavaria raised his pension to £1200 per annum. A house, Rue d'Anjou, No. 39, was purchased for six thousand guineas, and Rumford expended much thought and energy in making it, with its garden of two acres, all that he could desire. But the union was not so happy as he anticipated. The count loved quiet; Madame de Rumford was fond of company: to the former the pleasure of the table had no charms; the latter took delight in sumptuous dinner-parties. As time went on, domestic affairs became more and more unpleasant, and at length a friendly separation was agreed upon, after they had lived together for about three years and a half. The count then retired to a small estate which he hired at Auteuil, about four miles from Paris. The Elector of Bavaria was crowned king on January 1, 1806, and in 1810 Rumford was again at Munich, for the purpose of forming, at the king's request, an Academy of Arts and Sciences. At Auteuil the count was joined by his daughter in December, 1811, her journey having been much delayed through the capture of the vessel in which she had taken her passage, off Bordeaux. An engraving of the house at Auteuil, and the room in which Rumford carried on his experiments, was published in the Illustrated London News of January 22, 1870.

While resident at Auteuil, Rumford frequently read papers before the Institute of France, of which he was a member. He complained very much of the jealousy exhibited by the other members with reference to any discoveries made by a foreigner. He died in his house at Auteuil, on August 21, 1814, in the sixty-second year of his age. In 1804 he had made over, by deed of gift to his mother, the sum of ten thousand dollars, that she might leave it by will to her younger children. As before mentioned, Harvard College was his residuary legatee, and the property so bequeathed founded the Rumford Professorship in that institution.

Cuvier, as Secretary of the Institute, pronounced the customary eulogy over its late member. The following passages throw some light on the reputation in which the count was held:—

He has constructed two singularly ingenious instruments of his own contriving. One is a new calorimeter for measuring the amount of heat produced by the combustion of any body. It is a receptacle containing a given quantity of water, through which passes, by a serpentine tube, the product of the combustion; and the heat that is generated is transmitted through the water, which, being raised by a fixed number of degrees, serves as the basis of the calculations. The manner in which the exterior heat is prevented from affecting the experiment is very simple and very ingenious. He begins the operation at a certain number of degrees below the outside heat, and terminates it at the same number of degrees above it. The external air takes back during the second half of the experiment exactly what it gave up during the first. The other instrument serves for noting the most trifling differences in the temperature of bodies, or in the rapidity of its changes. It consists of two glass bulbs filled with air, united by a tube, in the middle of which is a pellet of coloured spirits of wine; the slightest increase of heat in one of the bulbs drives the pellet towards the other. This instrument, which he called a thermoscope, was of especial service in making known to him the varied and powerful influence of different surfaces in the transmission of heat, and also for indicating a variety of methods for retarding or hastening at will the processes of heating and freezing....

He thought it was not wise or good to entrust to men, in the mass, the care of their own well-being. The right, which seems so natural to them, of judging whether they are wisely governed, appeared to him to be a fictitious fancy born of false notions of enlightenment. His views of slavery were nearly the same as those of a plantation-owner. He regarded the government of China as coming nearest to perfection, because, in giving over the people to the absolute control of their only intelligent men, and in lifting each of those who belonged to this hierarchy on the scale according to the degree of his intelligence, it made, so to speak, so many millions of arms the passive organs of the will of a few sound heads—a notion which I state without pretending in the slightest degree to approve it, and which, as we know, would be poorly calculated to find prevalence among European nations.

As for the rest, whatever were the sentiments of M. Rumford for men, they in no way lessened his reverence for God. He never omitted any opportunity in his works of expressing his religious admiration of Providence, and of proposing for that admiration by others, the innumerable and varied provisions which are made for the preservation of all creatures; indeed, even his political views came from his firm persuasion that princes ought to imitate Providence in this respect by taking charge of us without being amenable to us.

In front of the new Government offices and the National Museum in the Maximilian Strasse, in Munich, stand, on granite pedestals, four bronze figures, ten feet in height. These represent General Deroy, Fraunhofer, Schelling, and Count Rumford. The statue of Rumford was erected in 1867, at the king's private expense. In the English garden which Rumford planned and laid out is the monument erected during his absence in England in 1796, and bearing allegorical figures of Peace and Plenty, and a medallion of the count.

The bare enumeration of Rumford's published papers would occupy considerable space, but many of them have more to do with philanthropy and domestic economy than with physics. We have seen that, when guest of Lord George Germaine, he was engaged in experiments on gunpowder. The experiments were made in the usual manner by firing bullets into a ballistic pendulum, and recording the swing of the pendulum. Thompson suggested a modification of the ballistic pendulum, attaching the gun-barrel to the pendulum, and observing the recoil, and making allowance for the recoil due to the discharge from the gun of the products of combustion of the powder, the excess enabled the velocity of the bullet to be calculated. Afterwards he made experiments on the maximum pressure produced by the explosion of powder, and pointed out that the value of powder in ordnance does not depend simply on the whole amount of gas produced, but also on the rapidity of combustion. While superintending the arsenal at Munich, Rumford exploded small charges of powder in a specially constructed receiver, which was closed by a plug of well-greased leather, and on this was placed a hemisphere of steel pressed down by a 24-pounder brass cannon weighing 8081 pounds. He found that the weight of the gun was lifted by the explosion of quantities of powder varying from twelve to fifteen grains, and hence concluded that, if the products of combustion of the powder were confined to the space actually occupied by the solid powder, the initial pressure would exceed twenty thousand atmospheres. Rumford's calculation of the pressure, based upon the bursting of a barrel, which he had previously constructed, is not satisfactory, inasmuch as he takes no account of the fact that the inner portions of the metal would give way long before the outer layers exerted anything like their maximum tension. When a hollow vessel with thick walls, such as a gun-barrel or shell, is burst by gaseous pressure from within, the inner layers of material are stretched to their breaking tension before they receive much support from the outer layers; a rift is thus made in the interior, into which the gas enters, and the surface on which the gas presses being thus increased, the rift deepens till the fracture is complete. In order to gain the full strength due to the material employed, every portion of that material should be stretched simultaneously to the extent of its maximum safe load. This principle was first practically adopted by Sir W. G. Armstrong, who, by building up the breech of the gun with cylinders shrunk on, and so arranged that the tension increased towards the exterior, availed himself of nearly the whole strength of the metal employed to resist the explosion. Had Rumford's barrel been constructed on this principle, he would have obtained a much more satisfactory result.

These investigations were followed by a very interesting series of experiments on the conducting power of fluids for heat, and, although he pushed his conclusions further than his experiments warranted, he showed conclusively that convection currents are the principal means by which heat is transferred through the substance of fluids, and described how, when a vessel of water is heated, there is generally an ascending current in the centre, and a descending current all round the periphery. Hence it is only when a liquid expands by increase of temperature that a large mass can be readily heated from below. Water below 39° Fahr. contracts when heated. Rumford, in his paper, enlarges on the bearing of this fact on the economy of the universe, and the following extracts afford a good specimen of his style, and justify some of the statements made by Cuvier in his eulogy:—

I feel the danger to which a mortal exposes himself who has the temerity to undertake to explain the designs of Infinite Wisdom. The enterprise is adventurous, but it cannot surely be improper.

The wonderful simplicity of the means employed by the Creator of the world to produce the changes of the seasons, with all the innumerable advantages to the inhabitants of the earth which flow from them, cannot fail to make a very deep and lasting impression on every human being whose mind is not degraded and quite callous to every ingenuous and noble sentiment; but the further we pursue our inquiries respecting the constitution of the universe, and the more attentively we examine the effects produced by the various modifications of the active powers which we perceive, the more we shall be disposed to admire, adore, and love that great First Cause which brought all things into existence.

Though winter and summer, spring and autumn, and all the variety of the seasons are produced in a manner at the same time the most simple and the most stupendous (by the inclination of the axis of the earth to the plane of the ecliptic), yet this mechanical contrivance alone would not have been sufficient (as I shall endeavour to show) to produce that gradual change of temperature in the various climates which we find to exist, and which doubtless is indispensably necessary to the preservation of animal and vegetable life....

But in very cold countries the ground is frozen and covered with snow, and all the lakes and rivers are frozen over in the very beginning of winter. The cold then first begins to be extreme, and there appears to be no source of heat left which is sufficient to moderate it in any sensible degree.

Let us see what must have happened if things had been left to what might be called their natural course—if the condensation of water, on being deprived of its heat, had followed the law which we find obtains in other fluids, and even in water itself in some cases, namely, when it is mixed with certain bodies.

Had not Providence interfered on this occasion in a manner which may well be considered miraculous, all the fresh water within the polar circle must inevitably have been frozen to a very great depth in one winter, and every plant and tree destroyed; and it is more than probable that the region of eternal frost would have spread on every side from the poles, and, advancing towards the equator, would have extended its dreary and solitary reign over a great part of what are now the most fertile and most inhabited climates of the world!...

Let us with becoming diffidence and awe endeavour to see what the means are which have been employed by an almighty and benevolent God to protect His fair creation.

He then goes on to explain how large bodies of water are prevented from freezing at great depths on account of the expansion which takes place on cooling below 39° Fahr., and the further expansion which occurs on freezing, and mentions that in the Lake of Geneva, at a depth of a thousand feet, M. Pictet found the temperature to be 40° Fahr.

"We cannot sufficiently admire the simplicity of the contrivance by which all this heat is saved. It well deserves to be compared with that by which the seasons are produced; and I must think that every candid inquirer who will begin by divesting himself of all unreasonable prejudice will agree with me in attributing them both to the same Author....

"But I must take care not to tire my reader by pursuing these speculations too far. If I have persisted in them, if I have dwelt on them with peculiar satisfaction and complacency, it is because I think them uncommonly interesting, and also because I conceived that they might be of value in this age of refinement and scepticism.

"If, among barbarous nations, the fear of a God, and the practice of religious duties, tend to soften savage dispositions, and to prepare the mind for all those sweet enjoyments which result from peace, order, industry, and friendly intercourse; a belief in the existence of a Supreme Intelligence, who rules and governs the universe with wisdom and goodness, is not less essential to the happiness of those who, by cultivating their mental powers, HAVE LEARNED TO KNOW HOW LITTLE CAN BE KNOWN."

Rumford, in connection with his experiments on the conducting power of liquids, tried the effect of increasing the viscosity of water by the addition of starch, and of impeding its movements by the introduction of eider-down, on the rate of diffusion of heat through it. Hence he explained the inequalities of temperature which may obtain in a mass of thick soup—inequalities which had once caused him to burn his mouth—and, applying the same principles to air, he at once turned his conclusions to practical account in the matter of warm clothing.

After an attempt to determine, if possible, the weight of a definite quantity of heat—an attempt in which very great precautions were taken to exclude disturbing causes, while the balance employed was capable of indicating one-millionth part of the weight of the body weighed—Rumford, finding no sensible effect on the balance, concluded that "if the weight of gold is neither augmented nor lessened by one-millionth part, upon being heated from the point of freezing water to that of a bright red heat, I think we may very safely conclude that ALL ATTEMPTS TO DISCOVER ANY EFFECT OF HEAT UPON THE APPARENT WEIGHTS OF BODIES WILL BE FRUITLESS." The theoretical investigations of Principal Hicks, based on the vortex theory of matter and the dynamical theory of heat, have recently led him to the conclusion that the attraction of gravitation may depend to some extent on temperature.

A series of very valuable experiments on the radiating powers of different surfaces showed how that power varied with the nature of the surface, and the effect of a coating of lamp-black in increasing the radiating power of a body. In order to determine the effect of radiation in the cooling of bodies, Rumford employed the thermoscope referred to by Cuvier. The following passage is worthy of attention, as the truth it expounds in the last thirteen words appears to have been but very imperfectly recognized many years after it was written:—

"All the heat which a hot body loses when it is exposed in the air to cool is not given off to the air which comes into contact with it, but ... a large proportion of it escapes in rays, which do not heat the transparent air through which they pass, but, like light, generate heat only when and where they are stopped and absorbed."

Rumford then investigated the absorption of heat by different surfaces, and established the law that good radiators are good absorbers; and recommended that vessels in which water is to be heated should be blackened on the outside. In speculating on the use of the colouring matter in the skin of the negro, he shows his fondness for experiment:—

"All I will venture to say on the subject is that, were I called to inhabit a very hot country, nothing should prevent me from making the experiment of blackening my skin, or at least, of wearing a black shirt, in the shade, and especially at night, in order to find out if, by those means, I could contrive to make myself more comfortable."

In his experiments on the conduction of heat, Rumford employed a cylinder with one end immersed in boiling water and the other in melting ice, and determined the temperature at different points in the length of the cylinder. He found the difficulty which has recently been forcibly pointed out by Sir Wm. Thomson, in the article "Heat," in the "EncyclopÆdia Britannica," viz. that the circulation of the water was not sufficiently rapid to keep the temperature of the layer in contact with the metal the same as that of the rest of the water; and he also called attention to the arbitrary character of thermometer-scales, and recommended that more attention should be given to the scale of the air thermometer. It was in his visit to Edinburgh, in 1800, that, in company with some of the university professors, the count conducted some experiments in the university laboratory on the apparent radiation of cold. Rumford's views respecting frigorific rays have not been generally accepted, and Prevost's theory of exchanges completely explains the apparent radiation of cold without supposing that cold is anything else than the mere absence of heat.

We must pass over Rumford's papers on the use of steam as a vehicle of heat, on new boilers and stoves for the purpose of economizing fuel, and all the papers bearing on the nutritive value of different foods. The calorimeter with which he determined the amount of heat generated by the combustion, and the latent heat of evaporation, of various bodies has been already alluded to. Of the four volumes of Rumford's works published by the American Academy of Arts and Sciences, the third is taken up entirely with descriptions of fireplaces and of cooking utensils.

Before deciding on the best way to light the military workhouse at Munich, Rumford made a series of experiments on the relative economy of different methods, and for this purpose designed his well-known shadow-photometer. In the final form of this instrument the shadows were thrown on a plate of ground glass covered with paper, forming the back of a small box, from which all extraneous light was excluded. Two rods were placed in front of this screen, and the lights to be compared were so situated that the shadow of one rod thrown by the first light might be just in contact with that of the other rod thrown by the second light. By introducing coloured glasses in front of the lights, Rumford compared the illuminating powers of different sources with respect to light of a particular colour. The complementary tints exhibited by the shadows caused him to devise his theory of the harmony of complementary colours. One result is worthy of mention: it is a conclusion to which public attention has since been called in connection with "duplex" burners. Rumford found that with wax tapers the amount of light emitted per grain of wax consumed diminished with the diminution of the consumption, so that a small taper gave out only one-sixteenth as much light as an ordinary candle for the same consumption of wax. He says:—

"This result can be easily explained if we admit the hypothesis which supposes light to be analogous to sound.... The particles ... were so rapidly cooled ... that they had hardly time to shine one instant before they became too cold to be any longer visible."

An argand lamp, when compared with a lamp having a flat wick, gave more light in the ratio of 100 to 85 for the same consumption of oil.

One of the latest investigations of Rumford was that bearing on the effect of the width of the wheels on the draught of a carriage. To his own carriage, weighing, with its passengers, nearly a ton, he fitted a spring dynamometer by means of a set of pulleys attached to the under-carriage and the splinter-bar. He used three sets of wheels, respectively 1-3/4, 2-1/4, and 4 inches wide, and, introducing weights into the carriage to make up for the difference in the weights of the wheels, he found a very sensible diminution in the tractive force required as the width of the wheels was increased, and in a truly scientific spirit, despising the ridicule cast upon him, he persisted in riding about Paris in a carriage with four-inch tyres.

But the piece of work by which Rumford will be best known to future generations is that described in his paper entitled "An Inquiry concerning the Source of the Heat which is excited by Friction." It was while superintending the boring of cannon in the arsenal at Munich that Rumford was struck with the enormous amount of heat generated by the friction of the boring-bar against the metal. In order to determine whether the heat had come from the chips of metal themselves, he took a quantity of the abraded borings and an equal weight of chips cut from the metal with a fine saw, and, heating them to the temperature of boiling water, he immersed them in equal quantities of water at 59-1/2° Fahr. The change of temperature of the water was the same in both cases, and Rumford found that there was no change which he could discover in regard to its capacity for heat produced in the metal by the action of the borer.

In order to prevent the honeycombing of the castings by the escaping gas, the cannon were cast in a vertical position with the breech at the bottom of the mould and a short cylinder projecting about two feet beyond the muzzle of the gun, so that any imperfections in the casting would appear in this projecting cylinder. It was on one of these pieces of waste metal, while still attached to the gun, that Rumford conducted his experiments. Having turned the cylinder, he cut away the metal in front of the muzzle until the projecting piece was connected with the gun by a narrow cylindrical neck, 2·2 inches in diameter and 3·8 inches long. The external diameter of the cylinder was 7·75 inches, and its length 9·8 inches, and it was bored to a depth of 7·2 inches, the diameter of the bore being 3·7 inches. The cannon was mounted in the boring-lathe, and a blunt borer pressed by a screw against the bottom of the bore with a force equal to the weight of 10,000 pounds. A small transverse hole was made in the cylinder near its base for the introduction of a thermometer. The cylinder weighed 113·13 pounds, and, with the gun, was turned at the rate of thirty-two revolutions per minute by horse-power. To prevent loss of heat, the cylinder was covered with flannel. After thirty minutes' work, the thermometer, when introduced into the cylinder, showed a temperature of 130° Fahr. The loss of heat during the experiment was estimated from observations of the rate of cooling of the cylinder. The weight of metal abraded was 837 grains, while the amount of heat produced was sufficient to raise nearly five pounds of ice-cold water to the boiling point.

To exclude the action of the air, the cylinder was closed by an air-tight piston, but no change was produced in the result. As the air had access to the metal where it was rubbed by the piston, and Rumford thought this might possibly affect the result, a deal box was constructed, with slits at each end closed by sliding shutters, and so arranged that it could be placed with the boring bar passing through one slit and the narrow neck connecting the cylinder with the gun through the other slit, the sliding shutters, with the help of collars of oiled leather, serving to make the box water-tight. The box was then filled with water and the lid placed on. After turning for an hour the temperature was raised from 60° to 107° Fahr., after an hour and a half it was 142° Fahr., at the end of two hours the temperature was 178° Fahr., at two hours and twenty minutes it was 200° Fahr., and at two hours and thirty minutes it ACTUALLY BOILED!

"It would be difficult to describe the surprise and astonishment expressed in the countenances of the bystanders on seeing so large a quantity of cold water heated and actually made to boil without any fire.

"Though there was, in fact, nothing that could justly be considered as surprising in this event, yet I acknowledge fairly that it afforded me a degree of childish pleasure which, were I ambitious of the reputation of a grave philosopher, I ought most certainly rather to hide than to discover."

Rumford estimated the "total quantity of ice-cold water which, with the heat actually generated by the friction and accumulated in two hours and thirty minutes, might have been heated 180 degrees, or made to boil" at 26·58 pounds, and the rate of production he considered exceeded that of nine wax candles, each consuming ninety-eight grains of wax per hour, while the work of turning the lathe could easily have been performed by one horse. This was the first rough attempt ever made, so far as we know, to determine the mechanical equivalent of heat.

In his reflections on these experiments, Rumford writes:—

It is hardly necessary to add that anything which any insulated body or system of bodies can continue to furnish without limitation cannot possibly be a material substance; and it appears to me to be extremely difficult, if not quite impossible, to form any distinct idea of anything capable of being excited and communicated in the manner the heat was excited and communicated in these experiments, except it be MOTION.

It has been stated that, if Rumford had dissolved in acid the borings and the sawn strips of metal, the capacity for heat of which he determined, and had shown that the heat developed in the solution was the same in the two cases, his chain of argument would have been absolutely complete. Considering the amount of heat produced in the experiments, there are few minds whose conviction would be strengthened by this experiment, and it is only those who look for faultless logic that will refuse to Rumford the credit of having established the dynamical nature of heat.

Davy afterwards showed that two pieces of ice could be melted by being rubbed against one another in a vacuum, but he does not appear to have made as much as he might of the experiment. Mayer calculated the mechanical equivalent of heat from the heat developed in the compression of air, but he assumed, what afterwards was shown by Joule to be nearly true, that the whole of the work done in the compression was converted into heat. It was Joule, however, who first showed that heat and mechanical energy are mutually convertible, so that each may be expressed in terms of the other, a given quantity of heat always corresponding to the same amount of mechanical energy, whatever may be the intermediate stages through which it passes, and that we may therefore define the mechanical equivalent of heat as the number of units of energy which, when entirely converted into heat, will raise unit mass of water one degree from the freezing point.