METEOROLOGY. ^TEMPERATURE 415 



the farmer of a foreknowledge of the quantity of manure which he 

 may reasonable calculate on obtaining from a known weight of forage 

 consumed upon his premises. Of the various methods proposed foi 

 arriving at this information, that which I have employed, and which 

 is based on ascertaining the amount of azote, appears to me the best 

 calculated to supply satisfactory results, particularly when experience 

 shall have corrected or confirmed the numbers which I have adopted 

 as the elements of my calculations. 



I have already said that any supplementary forage, or forage 

 added to that which is indispensable to the production of manure, 

 generally acquires, by the fact of its conversion into power or into 

 exportable substances, a value superior to that which it could have 

 had of itself in the market place. This additional forage is that 

 fraction of the provender, the azote of which figures in the statements 

 that have just been made as azote exhaled or assimilated and fixed. 

 We find, in fact, in representing this forage which is lost to the 

 dung-heap, but gained to power and exportable articles, that in the 

 stall, 100 lbs. of hay yield 8.6 lbs. of live weight, and 40.8 lbs. of 

 milk, and that in the hog-stye, 100 lbs. of hay yield 21 of living 

 weight. In the stable, again, the azote fixed, exhaled, or lost amounte 

 to nearly 1540 lbs., represented by about 1218 cwts. of hay, which 

 have yielded 1504 lbs. of live weight, due in great part to the birth 

 and growth of foals, in addition to the force represented by 8370 

 days' work. 



CHAPTER IX. 



METEOROLOGICAL CONSTDERA.TIONS. 

 g 1. TEMPERATURE. 



The phenomena of vegetation are always accomplished under the 

 influence of a certain temperature. If, in addition, the concurrence 

 of light, air, moisture, and various inorganic substances, be required, 

 it is still perfectly certain that all of these agents only contribute to 

 the development of a plant when they are assisted by a due measure 

 of heat, variable with reference to the different vegetable species, 

 and comprised within limits that are rather far apart, but essential. 

 Germination, for example, takes place at a temperature a few degrees 

 above the freezing point of water, 38° or 39° P., and at one indica- 

 ted by 100° or 120° of the same scale. The forests of tropical 

 countries thrive in a hot, moist atmosphere, which often marks up- 

 wards of 100° P. ; and I met with a saxifrage upon the Andes at 

 an elevation of 15,748 feet above the level of the sea, beyond the 

 line of perpetual snow, and very near the line of perpetual con* 

 gelation. 



Some families of plants require a temperature not only high, but 

 that never falls bolow a certain very limited degree ; the majority 



