BONES. 279 



iowns. The large quantity of azote contained in these manures 

 sliows how their value may be such as to permit of their being 

 advantageously exported to great distances beyond seas. 



Bones are employed in agriculture after having had the fat which 

 they contained extracted from them by boiling. They are crushed 

 by being passed between the teeth or grooves of a couple of cast- 

 iron rollers. They must be regarded as a manure, the action of 

 which is of long duration, because the animal matter contained in 

 them decomposes slowly, protected as it is by the earthy casing 

 which surrounds it. In England from 50 to 60 bushels of bruised 

 bones per acre are usually put upon land prepared for turnips. 



The employment of bones as manure has given rise to the most 

 various and contradictory observations. In certain circumstances 

 their effect upon vegetation has been almost null ; in others their 

 action has been decisive and most favorable. M. Payen has given 

 a solution of these anomalies which is perfectly satisfactory. Ac- 

 cording to my learned colleague, bones in their interstices, contain 

 a quantity of fat of various consistency, which may be removed by 

 long boiling in water ; the average quantity of grease obtained from 

 fresh bones is about 10 per cent. It has been observed that this fat- 

 ty matter diminishes gradually in bones that dry by long exposure ; 

 it even disappears almost entirely when they are dried at a high 

 temperature. This happens from the water which is disengaged 

 from the bony tissue by the effect of evaporation, being replaced by 

 fat melted by the heat. The consequence of this is, that the organic 

 tissue of bone, which was already sufficiently rebellious to decom- 

 position, becomes still less alterable when it is impregnated with 

 grease. The grease, in fact, by reacting upon the carbonate of 

 lime of the bone, has formed an earthy soap which long resists at- 

 mospherical influences and change under ground. 



It will readily be understood that bones in this condition can have 

 little or no action upon vegetation, unless indeed they be reduced to 

 very fine powder. This alone will explain how it may happen that 

 somg bones, after having remained four years in the ground, have 

 been found to have lost no more than 8 per cent, of their Vi^eight, 

 while those, the grease of which has been removed by boiling water, 

 have lost in the same space of time from 25 to 30 per cent, of their 

 weight.* 



These observations of M. Payen show how completely Schwertz 

 was mistaken when he ascribed the indifferent quality of the ma- 

 nure prepared from old bones, or from bones that had been boiled, 

 to the absence of fat, which he regards, I know not on what 

 authority, as a substance extremely favorable to vegetation. It is 

 not very obvious how fatty substances should act as manures. I 

 myself ascertained, from experiments made some years ago with 

 a view to test the conclusions of an agriculturist who ascribed 

 the good effects of cake to the fatty matters which it containen, 

 that rape-oil had no kind of favorable influence upon the growth 



* Paj-en, Maison Pusfique, v. i. p. 194. 



