“Dark Lightning.”—The attention of meteorologists and photographers has been engaged to a considerable extent, within a few months past, with the appearance on photographs of lightning of what seemed to be dark flashes as well as bright ones. In the effort to account satisfactorily for the phenomenon it has been referred to photographic reversal, due to extreme brilliancy; to a predominance of infra-red radiations; to the existence of flashes deficient in actinic rays; to changes in the density of the air occasioned by the spark, when a dark line with a light line within it is shown if the air is compressed, and a light line inclosing a dark one if it is rarefied; and to some qualities of the photographic plate. The first real light was thrown on the subject by some experiments described by Mr. A.W. Clayden, who, having photographed some electric sparks of different intensities, before developing the plates exposed them to the diffused light of a gas flame. The brilliant sparks then yielded images which might either be called normal with a reversed margin, or reversed with a normal core, while the fainter images were completely reversed—or, in other words, came out darker than the background. The “fogging” of the picture, to produce this reversal, must be done after the image of the flash is impressed; for if it is done before, the image appears lighter than the background. This effect, which is called the “Clayden effect,” is accepted as a satisfactory explanation of the phenomenon by two of the authors who have most studied it—Dr. W.J.S. Lockyer and Prof. R.W. Wood, of the University of Wisconsin. Professor Wood, on repeating Mr. Clayden’s experiment, obtained dark flashes without any difficulty, but as they failed to appear when the light of an incandescent lamp was substituted for the electric spark, he concludes that there is something in the spark essential to the reversal. Dr. Lockyer summarizes his conclusion by saying that dark-lightning flashes “do not exist in Nature, but their appearances on photographs are due to some chemical action which takes place in the gelatin film.”

“Warming Up.”—“Warming up” is the expressive term of general currency, which Dr. E.G. Lancaster adopts to denote the process in which one starting on any work in a little while suffers a short period of fatigue, from which he soon recovers, to go on with new and increased vigor. This occurs in the course of walks, with students engaged in earnest reading or in writing, and in animals, as in dogs on the chase, the animals pursued, and racehorses. “It is said of two famous trotters, each of which has reduced the world’s record within a few years, that the period of warming up was very characteristic.... Athletes, especially ball players, realize the importance of practice just before the games, to be followed by a slight rest. A pitcher would hardly enter the box till he had got his arm in working order by a few minutes’ practice. Orators often are dull at first, but warm up. It is said that Wendell Phillips was often hissed for his slow, uninteresting speech, but rallied to the occasion at such times with his masterly oratory.” Dr. Lancaster has experimented on the phenomena, using a method like those of Mosso and of Lombard in the psychological laboratory at Clark University, and publishes the results, with details and curves, in the papers of the Colorado College Scientific Society. He tried ten or twelve subjects, experimenting on the middle finger of the right hand, and gaining most of his results from four or five persons. He finds that warming up is general, but not universal. One subject always did his best work first. He likewise showed no warming up in his mental work. The phenomenon called “second mind” is closely allied to warming up, but is not the same. The author is of the opinion that the importance of this process is greatly misunderstood.

Sixty Years’ Improvements in Steamships.—A review of what has been accomplished in sixty years in the improvement of transatlantic traffic, given by Sir William H. White in his address at the British Association on Steam Navigation at High Speeds, shows that speed has been increased from eight and a half to twenty-two and a half knots an hour, and the time of the voyage has been brought down to about thirty-eight per cent of what it was in 1838. Ships have been more than trebled in length, about doubled in breadth, and increased tenfold in displacement. The number of passengers carried by a steamship has been enlarged from about one hundred to nearly two thousand. The engine power has been made forty times as great. The ratio of horse power to the weight driven has been quadrupled. The rate of coal consumption per horse power per hour is now only about one third what it was in 1840. Had the old rate of coal consumption continued, instead of three thousand tons of coal, nine thousand would have been required for a voyage at twenty-two knots. Had the engines been proportionately as heavy as those in use sixty years ago, they would have weighed about fourteen thousand tons. In other words, machinery, boilers, and coal would have exceeded the total weight of the Campania as she floats to-day. “There could not be a more striking illustration than this of the close relation between improvements in marine engineering at high speed. Equally true is it that this development could not have been accomplished but for the use of improved materials and structural arrangements.”

American Advances in Forestry.—The Department of Agriculture having determined to prepare a book for the Paris Exposition, reviewing what has been accomplished in scientific agriculture in the United States, the Division of Forestry will contribute to it a short history of forestry in the United States, with an account of the efforts of private landholders to apply the principles of forestry. Much more has been accomplished in the United States in the way of forestry than has been supposed. Mr. Pinchot, the forester of the division, holds that wherever private owners have made the effort to use the merchantable timber on their woodland without injuring its productive power, and to establish new forests, there has been the intention of true forestry. The methods may have been imperfect, but they have tended toward economic forest management so far as their object was the continued use of the land for producing woods. Among the measures looking in this direction Mr. Pinchot mentions in his circular the practice which has been adopted “because it pays,” in some of the spruce lands of the Northwest, of leaving the small trees standing, so that the lumbermen can return for a second crop earlier than would otherwise be possible; and the adoption by farmers of methods in getting their wood, for saving the best trees and promoting their growth and that of the new ones; of keeping sprout lands to be cut over regularly and systematically, for periodical renewal, and of tree planting on waste places, hillsides liable to be washed, and the banks of streams. Other forms of planting are the institution of wind breaks in the treeless West, and special plantations for fence posts, etc. A kind of forestry practice is likewise indicated in the special pains that are taken by farmers and in lumbering districts to lessen the danger of fires. Forester Pinchot desires that all the information that can be gained be communicated to him for the proposed article.

Professor Putnam on the Origins of the American Races.—In his address as retiring President of the American Association, Prof. F.W. Putnam, after expressing his high opinion of the late Dr. D.G. Brinton and his scientific labors, referred to the differences of opinion that had existed between them in respect to the origin of the American peoples, and proceeded to expound his own views on the subject. He regarded the term “mound-builders” as comprehensive enough to include all the peoples who had left the marks of their former presence in this country. Even the shell heaps could not be regarded as the work of one people. From the time of the earliest deposits—which were of great antiquity—to the present, such refuse piles had been made and many of the sites reoccupied, sometimes even by a different people. So with the mounds of earth and stone; many of them are of great antiquity, while others were made within the historic period, and even during the first half of the present century. These works were devoted to a variety of purposes, and there are many different kinds of them. Besides the mounds, there are groups of earthworks of a different order of structure, that must be considered by themselves—great embankments, fortifications, and singular structures on hills and plateaus that are in marked contrast to the ordinary conical mounds, and mounds in the form of animals and of man. The considerable antiquity of these older earthworks is proved by the accumulation of mold and the forest growth upon them. “If all mounds of shell, earth, or stone, fortifications on hills, or places of religious and ceremonial rites, are classed, irrespective of their structure, contents, or time of formation, as the work of one people, and that people is designated as the ‘American Indian’ or the ‘American race,’ and considered the only people ever inhabiting America north and south, we are simply ... not giving fair consideration to differences, while overestimating resemblances.” Citing analogies between our earthworks and Mexican structures, and looking upon the Pueblos as a connecting link, “we must regard the culture of the builders of the ancient earthworks as one and the same with that of ancient Mexico, although modified by environment. Our northern and eastern tribes came in contact with this people when they pushed their way southward and westward, and many of their arts and customs still linger among some of our Indian tribes. It is this absorption and admixture of the stocks that has in the course of thousands of years brought all our peoples into a certain uniformity. This does not, however, prove a unity of race.”

Heat Insulators.—Mr. C.L. Norton has made experiments, at the request of Mr. Edward Atkinson, in order to determine the relative efficiency of several kinds of steam-pipe covering now on the market; to ascertain the fire risk attendant upon the use of certain methods and materials employed for insulation of steam pipes; to show the gain in economy attendant upon the increase of thickness of coverings; and to find the exact financial return that may be expected from a given outlay for covering steam pipes. A method of experimentation was adopted which represented as nearly as practicable the conditions existing in the actual use of steam pipes. Of sixteen non-conducting preparations tried, the most efficient were found to be those made of cork; next was a cover composed of an inner jacket of earthy material and an outer jacket of wool felt; and next magnesia. In reference to the last substance it is, however, observed that, while it is a most effective non-conductor, the name has been applied to many compounds of which the greater part consist of carbonate of lime or plaster of Paris, materials which are not good as heat retardents. Asbestos is merely a non-combustible material in which air may be entrapped, but, when non-porous, is a good conductor of heat. Generally speaking, a cover saves heat enough to pay for itself in a little less than a year at three hundred and ten ten-hour days, and in about four months at three hundred and sixty-five twenty-four-hour days. The decision as to the choice of cover must, however, come from other considerations, as well as from that of non-conductivity. Ability to withstand the action of heat for a prolonged period without being destroyed or rendered less efficient is of vital importance. The cork coverings were found to respond to this test extremely well, and there can be no question respecting magnesia; but Mr. Norton does not consider it safe to put upon a steam pipe wool, hair, felt, or woolen felt in any form, though the danger is not likely to accrue when an inch of fireproof material stands between the felt and the pipe. In general it may be said that if five years is the life of a cover, one inch is the most economical thickness, while a cover which has a life of ten years may to advantage be made two inches thick. The method of judging a pipe cover by the warmth felt on putting the hand upon it is fallacious; the sensation depends so much upon the nature of the surface that it utterly fails to give any idea of the actual temperature.

Effect of Sea Water on Soil.—In a paper read at the British Association, 1899, on the chemical effect of the salts of the salt-water flood of November 27, 1897, on the east coast of England, Messrs. T.S. Dymond and F. Hughes recorded the remarkable result that, although the proportion of salt left in the soil was insufficient to prove injurious to growing crops, the earthworms were entirely removed, with the consequence that very few crops were worth harvesting the following year. In the next year nine tenths of the salt at first present had disappeared from the soil, and young worms had again made their appearance, but still the condition of the soil remained unsatisfactory, the rate of percolation of water through the flooded earth being only one half as rapid as through the unflooded. The authors ascribe this to the action of the chlorides of the sea water on the silicates of the soil with the formation of silicate of alumina in a gelatinous condition.

The War against Monopolies.—Mr. Robert Ewen writes, in the Westminster Review, demanding free bank circulation as likely to be a very effective weapon to be used in “the coming contest with monopolists.” The subject seems to have attracted official attention in England in 1875, when Sir Stafford Northcote was Chancellor of the Exchequer. As chairman of the committee appointed to inquire into the working of the Bank Acts, he submitted a memorandum showing that, while certain items of the monopoly enjoyed by the Bank of England had been withdrawn, a residuum of restrictions on issuing banks still remained unrepealed. Some other countries have found a way of giving elasticity to the currency by buying in and laying aside their bonds, as the United States has recently been doing. This can not be done in Great Britain, because the Bank of England and the other bank monopolists block the way. The bank is tied down by acts of Parliament to buy and sell gold at a fixed price, and this restriction has been a cause of panics, whereas had gold been allowed to rise and fall in price, according to supply and demand, and the bank got a free hand in dealing with that commodity and in issuing legal notes to supply the circulating medium, “all would have gone well.” Foreign protectionists now have the power to prevent British goods from getting into their markets by imposing heavy duties on them, and at the same time forcing their produce into British markets, because English laws allow them to get gold from the English cheaper than their goods can be obtained. “Suppose a merchant in Britain buys £100,000 worth of corn from America and gives a check on the Bank of England for the amount of the purchase. The American draws the £100,000 in gold and takes it home; he will have to pay no export or import duty thereon—indeed, the probability is he may get a premium on the gold in America. But reverse the transaction: Suppose the British merchant sold £100,000 worth of his goods to America, there would, in the first place, be the exorbitant duty imposed there upon our manufactures of from forty to fifty per cent. Or suppose our merchant wished to buy corn or any American produce in exchange for his goods in place of bringing money, the case would be different—it would tell against the American farmer, who would get a less price for his corn, etc., than he would have done by free trade.” This instance is given “to show how free trade in gold would bring about free trade and reciprocity between the United States and Britain, and is applicable to every other state with which we trade.... There should be full scope given to all good banks in the country, large or small, to carry on banking business in the best modern manner for the benefit of all parties, so as to encourage and develop all trades and industries.”

Rats and the Plague.—In his introductory address at the opening of the London School of Tropical Medicine, Dr. Manson preached a war of extermination against rats with the vigor of Cato calling for the destruction of Carthage. “Were I asked,” he said, “how I would protect a state from plague, I would certainly answer, Exterminate the rats as a first and most important measure.” He added, “At the present juncture, were I the responsible sanitary head of any town in Europe, in anticipation of a possibility compared to which in horror and in destructiveness a general European war would be a trifle, I would do my best to have every rat and, if possible, every mouse in my district promptly exterminated.” Dr. Manson does not reveal his plan of campaign. Wholesale poisoning of sewers might have serious disadvantages, and there would be difficulties about inveigling the rodent population of these subterranean health resorts (as some enthusiasts consider them to be) into a lethal chamber. Are we to cry havoc and let slip the cats of war? or to hurl an army of snakes against the foe? In either case we might find ourselves in the awkward position of a king who had called a too powerful auxiliary to his aid. Already action is being taken on the rat theory of plague. The French Government has ordered that special precautions are to be taken to prevent the importation of rats in vessels from plague-stricken places. It is to be hoped that similar precautions will be taken in regard to the transports which convey the Indian contingent to the Cape, or the situation there may become complicated by the intervention of an enemy who will deal destruction impartially to Boers and to Britons.

Forestry in California.—As a remedy for the devastation of the forest lands of California, Marsden Manson, having shown that Government administrations with politics in them can not be trusted in the matter, recommends that all forest reservations and public lands upon mountain slopes within the borders of the State be granted to the University of California in trust, for the purpose of maintaining, developing, and extending the water supply of those regions forever. For this purpose the regents should be empowered to lease, under proper control, the timber cutting and pasturage privileges of those areas, and to use the resultant fund to protect the catchment areas, to maintain a college of practical forestry, to construct reservoirs at such points as may be necessary to the industries of the State, and dispose of the water for the benefit of the trust, to acquire mountain lands to be added to the catchment areas, and to do all such things as may maintain wise systems of forest and water conservation and use. The extent of income-bearing property which can be made available for forest preservation and storage of flood waters, Mr. Manson says, is far beyond the general idea.

Another New Element.—The mineral pitchblende is distinguished for its radio-activity, or the property it has of emitting the peculiar light-rays which have recently attracted attention. The property has been attributed to the presence of uranium, one of the most radio-active among the known metals. About a year ago the chemists M. and Madame Curie, examining the different substances in pitchblende, found among them two new radiant substances, both more active than uranium, which they called polonium and radium. Polonium was found to be closely akin to bismuth, accompanying that metal in all its reactions, but separable from it by fractionation. Radium resembles barium in its chemical reactions. Recently M.A. Debierne, examining one of the products of solution and precipitation of pitchblende, observed intensified radio-active properties in a portion containing titanium, and on further investigation found still another substance showing the principal analytical properties of titanium, but which emitted extremely active rays. While these rays were comparable with those observed from polonium and radium, the chemical properties are entirely different from those of these substances. Radium, however, is spontaneously luminous, while the new substance is not.