 
3. A siphon, as is well known, is a bent tube, having one leg longer than the other. When this tube is filled with any liquid, and the shorter end is immersed in a vessel containing liquid of the same kind, the weight of the column in the longer leg will cause the liquid to begin to run out, and it will continue running till the vessel is emptied. This arises from the pressure of air on the exposed surface of fluid, forcing it up through the tube to prevent vacuum, which would otherwise be formed at the highest point; and the extreme limit of length at which the siphon will act is therefore determined by the height of a column of the fluid equal to the pressure of the atmosphere (fifteen pounds on the square inch). The limit in the case of water is something more than thirty feet. 4. ‘The Polar World,’ p. 54. 5. Liebig’s ‘Annalen,’ translated in ‘Reports and Memoirs of the Cavendish Society,’ London, 1848, p. 351. 6. See Chapter on Mines in general, for a short account of earth-boring operations. 7. ‘Die vulcanischen Erscheinungen der Erde.’ Liepzig, 1865. 9. A detailed account of this eruption, one of the most dreadful on record, is given in ‘The Polar World,’ chap. vi. p. 81. 10. Mallet, ‘The Great Neapolitan Earthquake of 1857,’ vol. i. p. 323. 11. Philosophical Transactions, vol. xlix. part i. p. 404. 12. It is almost superfluous to mention that in the Alps many of the peasants lead a migratory existence. During the summer they ascend, with their herds, into the higher valleys, where they remain, separated from their families, until the first night-frosts force them to return to their homes on a lower level. 13. ‘The Geology of South Australia.’ 14. ‘The Sea and its Living Wonders,’ 3rd edit. p. 49. 15. ‘The Sea and its Living Wonders,’ 3rd edit. p. 52. 16. ‘Description of the Island of Saint Michael.’ 17. ‘The Polar World,’ p. 58. 18. ‘Die HÖhlenkunde des Karstes.’ Wien, 1854. 19. ‘Flora Fribergensis Plantas Cryptogamicas prÆsertim subterraneas 20. ‘Vegetabilia in HercyniÆ Subterraneis collecta NorinbergÆ.’ 1811. 21. Torches are not allowed to be carried in the Grotto of Adelsberg, that the whiteness of the stalactites may not be tarnished by the smoke. 22. Voyages in the Lighthouse Yacht, published in Lockhart’s ‘Life of Sir Walter Scott.’ 23. Kinglake. 24. Shakespeare, ‘Tempest,’ iv. 1. 25. ‘The Crescent and the Cross.’ 26. ‘Ice Caves of France and Switzerland: a Narrative of Subterranean Exploration.’ By the Rev. G. F. Browne. Longmans, 1865. 27. Burslem, ‘A Peep into Toorkistan.’ 28. The Cave of Suitshellir. 29. ‘The Crescent and the Cross.’ 30. ‘On the Moa Caves of New Zealand.’ Edinburgh New Philosophical Journal, vol. lvi. 1854. 31. See also the article on Lacustrine Abodes, in the Edin. Review, July 1862. 32. Lyell, ‘Antiquity of Man,’ p. 101. 33. ‘Wanderungen durch Sicilien.’ 34. ‘Italy.’ 35. In the North of England the prices of boring in the ordinary strata of that coal-field are as follows:—
and so increasing 5s. 6d. per fathom on each succeeding depth of five fathoms. In boring through very hard strata the prices are from 80 to 100 per cent. higher. 36. ‘Life of Sterling,’ p. 278. 37. London: Longmans, 1857. 38. ‘Cornwall, its Mines and Miners.’ 39. Mr. Samuel Plimsoll (‘Letters on the Iron Trade,’ Times, February 10, 1868) informs us that in the Belgian coal mines the ventilation is carried on in a more economical and effective manner. Here no furnaces are lighted at the bottom of the upcast, because one-twentieth of the coal required for a furnace will make steam for an engine to work fans which act somewhat in the manner of huge paddle-wheels in steam-ships, and by rapid rotation over the shaft produce a draught which the incoming air rushes to meet, and thus powerfully promote ventilation. These fans they can work and control, and are therefore independent of those atmospheric influences to which some of our greatest calamities have been ascribed—the damp, heavy atmosphere of early winter. In the great colliery of SacrÉe Madame, near Charleroi, one of these fans will draw 34,000 cubic metres (about 918,000 cubic feet) per minute. 40. Recent improvements have done much to render the Davy lamp a more perfect instrument of safety. These more or less insure increased illumination, prevention of bad usage by locking, and more perfect combustion. By an ingenious contrivance, one of these improved lamps cannot be opened without previous extinguishment. 41. Experience has proved that when sulphuret of iron undergoes a chemical change into vitriol it disengages a sufficient quantity of heat to set fire to the coal with which it is often found mixed. 42. These names were borrowed from the Greek Drachma and the Latin Denarius. 43. ‘The Polar World,’ p. 231. 44. A very primitive contrivance for raising the water in skin bags. 45. Illustrated London News, No. 1477, Saturday, April 11, 1868. 46. The seventeenth chapter of ‘The Tropical World’ is devoted to the Erythroxylon Coca. 47. ‘Transactions of the Royal Geological Society of Cornwall,’ vol. v. p. 11. 48. ‘Cornwall, its Mines and Miners.’ London, 1860. 49. A reverberatory furnace is a furnace in which intense heat is produced by a flame which, while passing through a furnace, reverberates from the roof over the substance to be fused, the draught being created by means of a lofty chimney. 50. ‘Geological Travels through Sweden.’ 51. ‘Good luck upwards!’ or ‘A happy return to daylight.’ 52. This hybrid name, a vile compound of English and Greek, is enough to excite the wrath of a philologist. 53. Since the discovery of the rich North American and Chilian mines the price of copper has fallen about 30 per cent. The consequence has been a great diminution of our copper production. Thus Cornwall and Devonshire, which in 1856 yielded 206,177 tons of copper ore, worth 1,241,835l., saw their produce gradually diminish from that time, and in 1865 furnished no more than 159,409 tons, worth only 753,427l. In 1856 the mean average price of copper was 123l. per ton; in 1865 it was no more than 94l. 7s. 54. ‘Cornwall, its Mines and Miners.’ 55. The lodes in the Cornish tin and copper mines are divided by shafts and galleries into rectangular compartments, called ‘pitches.’ These are open to the inspection of all the labouring miners in the county, and, by an admirable system, each ‘pitch’ is let by public competition, for two months, to two or four or more miners, who may work it as they choose. These men agree to break the ores, wheel them, raise them to the surface, and bring them (if desired) into a fit condition for the market. The ores so raised are sold every week, and the miner immediately receives his tribute, or percentage for which he agreed to work. The sinking of shafts and the driving of levels is paid by tut-work, or task work, at so much per fathom. 56. The weight of the mass found at Otumpa, in the Gran Chaco Gualamba, in South America, by Don Rubin de Celis (1783) was estimated at about fifteen tons. A piece from this mass, weighing 1,400 pounds, is now in the British Museum. 57. ‘Quarterly Review,’ vol. cix. p. 114. 58. ‘History of the Iron Trade.’ 59. The metal was formerly so scarce in their country that in the times of the Edwards the Scotch were accustomed to make predatory incursions into England for the sake of the iron they could carry off. Now they not only manufacture sufficient for their own use, but actually export above half-a-million tons. 60. From the official reports of the International Jury of the Universal Exhibition of 1867 in Paris. 61. A coin of Nero, analysed by Arthur Phillips, was found to consist of 81·07 per cent. copper, 1·06 tin, and 17·73 zinc; another, of Hadrian, of 85·78 copper, 1·19 tin, 1·81 lead, 6·43 zinc, and 0·74 iron. 62. Kopp, ‘Geschichte der Chemie,’ vol. iv. p.221. 63. Lignite, or brown coal, is of more modern origin. 64. Vol. cxi. p. 80. 65. ‘Edinburgh Review,’ vol. cxi. p. 86. 66. Volume cx. 67. ‘Zeitschrift fÜr allgemeine Erdkunde,’ No. 84, Juni, 1860. 68. ‘The Polar World,’ p. 52. 69. ‘Urgeschichte Deutschlands.’ 70. The carat is equal to 3¼ grains Troy weight. 71. In the Brazilian diamond trade, the oitava (17½ carats) is considered as the unity of weight. It is subdivided into 4 quartas or 32 vintems; the vintem is equal to 218/100 grains. Stones of half a vintem still pass as good ware (fazenda ainda boa), when well-shaped and colourless. Middling ware (fazenda mediana) consists of from 64 to 100 stones to the oitava, while all below that weight is sold as refuse. Works by the same Author. THE SEA AND ITS LIVING WONDERS. With several hundred Wood Engravings; and an entirely New Series of Illustrations in Chromoxylography, representing the most Interesting Objects described in the Work, from Original Drawings by Henry Noel Humphreys. Third English Copyright Edition. 8vo. price 21s. ‘Dr. Hartwig’s volume is a perfect model of the popular treatment of a large subject. It is at once full, clear, concise, and attractive; and it possesses the merit, absolutely unique as far as our experience goes in works of this kind, of being readable from end to end. Though closely packed with details—sufficiently so indeed to be a good, though of course not an exhaustive, book of reference for practical use—these are so well selected and arranged, so concisely related, and so carefully subordinated to general views, that they never produce any sensation of weariness, monotony, or confusion. There are some admirable chromoxylographs, and an infinitude of excellent woodcuts scattered up and down the pages with a profuse hand. In short, the Sea has received from Dr. Hartwig a recommendation to public attention which can scarcely perhaps increase its popularity, but which will certainly enable many of its admirers to regard it with a more enlarged and intelligent admiration. The title, large as it is, does the work some injustice, for we are apt to forget the Sea itself in the Living Wonders which it nourishes; and we scarcely include, in our conception of life, the vegetation of the ocean. This, however, is no fault of Dr. Hartwig’s; for he fairly exhausts his subject. The first seventy pages are devoted to a very clear account of the general features of the sea. Its extent and depth and colour, its coast-line and currents, the height and velocity of its waves, the theory of its tides, the mighty circulation whereby the life-currents of the earth rise in evaporation from the ocean surface, are dispersed through the upper regions of the air, are condensed in rain, and, trickling through the soil, return in rivers to their native reservoir, are all set forth with great skill and beauty of language. Dr. Hartwig then passes on to the inhabitants of the sea. First come the “hugest of living things,” the Cetaceans, with their kindred the seals and walruses—animals which in their anatomy and habits form a curious link between the tribes of earth and Guardian, First Notice. ‘This is the third edition, considerably enlarged, of the first and best of Dr. Hartwig’s beautiful and popular volumes on natural history. The size of the book is increased by a hundred pages; a good deal of it is remoulded; two whole new chapters have been added, one on Marine Caves, the other on Marine Constructions, such as Lighthouses and Breakwaters; some of the old illustrations have disappeared, but their place has been supplied by more and better; so that the new edition really amounts to a recasting of the entire book. It was a very good book before; it is better and more complete now. Whether we regard the letterpress or the numerous illustrations, it takes a rank second to none among ornamental and popular books of science.’ Guardian, Second Notice. THE TROPICAL WORLD: a Popular Scientific Account of the Natural History of the Animal and Vegetable Kingdoms and the Equatorial Regions. With 8 Chromoxylographic Plates and about 800 Woodcuts. 8vo. price 21s. ‘This work well deserves popularity, and is just the book to interest young persons who have the sense to perceive that the truths of nature are not only stranger but far more profitable than some fictions. All that intelligent women and children desire to know about the tropics will be found here—the aspects of nature, the rivers and coasts, the great sandy deserts, the gigantic vegetation, and the animal denizens from insects to apes; but excluding the tropical varieties of man.’ Medical Times and Gazette. ‘Dr. Hartwig has followed up his admirable book on the Sea by another, not less admirable, on the Tropical World. The same wide erudition, vivid powers of description, and happy intermixture of popular and scientific treatment are displayed in it; and its pages are adorned by the same profusion of elegant illustration. Within the tropics Nature revels in her wildest luxuriance: bird, beast, reptile, and plant take there strange forms and colours, or attain unusual magnitude. Dr. Hartwig has steeped his pen in the glowing atmosphere of the tropics; and with it, as with a wand, he leads us through successive regions of a sunny fairyland teeming with beautiful natural objects in inexhaustible variety, changeful and brilliant as the effulgent landscapes amid which they flourish.’ Guardian. ‘The tropics give us something like a picture of the antediluvian world. The heat and moisture, with the consequent luxuriance of vegetation in tangled overgrowth, the violence of the storms, and the ferocity and hideousness of many animal forms, mark out these equatorial regions as very striking, very picturesque, very interesting, but not very Saturday Review. ‘We ought not to conclude these gleanings without a brief notice of Dr. Hartwig’s popular book. There are those who look with contempt on popular science of all kinds, and regard with undisguised aversion such compilations as the one before us. We do not share these feelings in the least degree; on the contrary, we welcome most heartily such introductions to the study of natural history. True, they may be sometimes of little scientific value, but they are very useful stepping-stones to something more solid. They are more especially intended for the young, but those of mature years may derive much profit by a perusal of many of these works, and even the naturalist may read them with pleasure and instruction. The numerous beautifully illustrated and carefully compiled works on natural history, such as the Tropical World, together with the Sea and its Living Wonders, by the same writer, and several others which have appeared within the last few years, are an encouraging sign of the growing interest which the rising generation takes in the study of the great Creator’s works, and we heartily wish them Godspeed.’ Quarterly Review. Works by the same Author. THE HARMONIES OF NATURE, OR THE UNITY OF CREATION. With 8 full-page Engravings on Wood, from Original Designs by F. W. Keyl, and about 200 Woodcuts in the Text. 8vo. price 18s. Globe. ‘Dr. Hartwig’s book at first looks like a system of natural history: it swarms with woodcuts of zoology and comparative anatomy. But it properly belongs to general psychology; for its object is comparison and deduction, and a view of the chain of being, which ... after some general cosmogony, begins at the lowest phases of vegetable life and ends with man.... The book is very interesting, and fills a very useful place.’ AthenÆum. ‘The nature of Dr. Hartwig’s Harmonies of Nature will perhaps be better understood if we call it a popularised Kosmos. Beginning with the starry heavens, the Author leads us through air and ocean, and shows in broad outline how material nature is adapted to the organic life which fills it. He then traces out the ascending grades of organic life itself from plants to sponges and jelly-fishes, and from them up through molluscs, Guardian. ‘The Harmonies of Nature will add to its Author’s well-deserved reputation as the most correct and philosophic as well as the most entertaining writer of the day on popular natural history. Unlike most of the compilers of this class of works, Dr. Hartwig has a very extensive knowledge of his subject, a knowledge sufficient to enable him to present to his readers a well-arranged work, that may be read with profit as well as with pleasure. The object of the work is to point out and illustrate the unity of plan which prevails throughout creation.... Compared with the popular natural histories current in France and England, the works of Dr. Hartwig are of much higher excellence; and for those readers who desire to know something about physical science without becoming painful and diligent students, no volume can be recommended as more delightful than the Harmonies of Nature.’ The Field. THE POLAR WORLD; A POPULAR DESCRIPTION OF MAN AND NATURE IN THE ARCTIC AND ANTARCTIC REGIONS OF THE GLOBE. With 8 Chromoxylographic Plates, 3 Maps, and 85 Woodcuts. 8vo. price 21s. Land and Water. London: LONGMANS and CO. Paternoster Row. Transcriber’s Note At At 198.9>, the paragraph ending ‘pillars supporting the roof’, includes a single closing quote, the opening of which is either missing, or it is itself a mistake. Given the wording of the paragraph, it is likely the latter. Errors deemed most likely to be the printer’s have been corrected, and are noted here. The references are to the page and line in the original, or where two columns were employed, the page, column, and line. Where the spelling of index entries disagree with their references in the text, they have been corrected.
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