Rural economy, in its relations with chemistry, physics and meteorology, tr. with an intr. and notes by G. Law (Google eBook)

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1845
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Page 677 - Humboldt, after the most careful examination of all the circumstances, did not hesitate to ascribe the diminution of the waters of the lake Valencia to the extensive clearings which had been effected in the course of half a century in the Aragua valley. " In felling the trees which covered the crowns and slopes of the mountains...
Page ix - ... obtained, are displayed with such absolute perspicuity as to be intelligible and instructive to every agricultural inquirer, however superficial his previous acquaintance may be with the details of chemical science. Nothing from the pen of the editor could throw additional light upon the author's most interesting elucidation of vegetable physiology ; his exposition is at once masterly and complete, and contains much that is both valuable and new.
Page 654 - This result is not only remarkable in so far as it seems to indicate that upon every parallel of latitude, at all elevations above the level of the sea, the same plant receives in the course of its existence an equal quantity of heat, but it may find its direct application by enabling us to foresee the possibility of acclimating a vegetable in a country, the mean temperature of the several months of which is known.
Page 266 - Chemists of great talent have made many complete analyses of soils noted for their fertility ; still practical agriculture has hitherto derived very slender benefits from labours of this kind. The reason of this is very simple ; the qualities which we esteem in a workable soil depend almost exclusively upon the mechanical mixture of its elements ; we are much less interested in its chemical composition than in this ; so that simple washing which shows the relations...
Page ix - The chemical portion of the work is of inestimable value and conducted with consummate skill and knowledge ; and with a minuteness and accuracy perfectly unexampled. At the same time the results of the writer's researches, as well as the means and processes by which these results were obtained, are displayed with such absolute perspicuity as to be intelligible and instructive to every agricultural inquirer, however superficial his previous acquaintance may be with the details of chemical science....
Page 654 - ... shorter as the mean temperature of the cycle itself is lower or higher. In other words, the duration of the vegetation appears to be in the inverse ratio of the mean temperature ; so that if we multiply the number of days during which a given plant grows in different climates, by the mean temperature of each, we obtain numbers that are very nearly equa...
Page 714 - SIX ETHNOGRAPHICAL MAPS, as a Supplement to the Natural History of Man, and to the Researches Into the Physical History of Mankind.
Page 493 - Beets about 11 pounds, of phosphoric acid, besides a very large quantity of potash and soda. It is obvious that such a process tends continually to exhaust arable land of the mineral substances useful to vegetation which it contains, and that a time must come, when, without supplies of such mineral matters, the land would become unproductive from their abstraction...
Page 216 - An English farmer," says Washington, in a letter addressed to Arthur Young, " must have a very indifferent opinion of our soil when he hears that with us an acre produces no more than from 8 to 10 bushels of wheat; but he must not forget that in all countries where land is cheap and labor is dear, the people prefer cultivating much to cultivating well.
Page 521 - ... their azotised principles, and consequently that their nutritious powers are in proportion to the quantity of azote they contain. From what precedes, however, it is obvious that I am far from regarding azotised principles alone as sufficient for the nutrition of animals ; but it is a fact, that very highly azotised vegetable nutritive substance is generally accompanied by the other organic and inorganic substances which concur in nutrition.

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