ANALYSIS OF ARABLE SOILS. 45 



I shall not point out the process of an analysis with the 

 most minute exactness ; this would place it beyond the 

 skill of the greater part of agriculturists to perform ; and 

 the precision of the results would be useless for the pur- 

 pose which I have in view. I shall limit myself to de- 

 scribing the steps which ought to be taken for ascertaining 

 the nature of the principal substances, whether earthy, 

 saline, metallic, vegetable, or animal, which enter into the 

 composition of a soil, whilst it is necessary to insist only 

 upon those which concur most powerfully in rendering it 

 fertile. 



In analyzing an earth, a small quantity of it should be 

 worked carefully by the hand before weighing it. The 

 first operation consists in drying this specimen carefully, 

 in order to know the weight of water it contains. For 

 this purpose it is placed in a vessel over the fire, of which 

 the heat must be just sufficient to evaporate the water. 

 This temperature must be preserved from fourteen to 

 twenty minutes. In order that no more heat than is 

 necessary may be applied, it is customary to put a bit of 

 wood at the bottom of the vessel, or a few bits of straw 

 into the earth subjected to the experiment, and to with- 

 draw it from the fire as soon as these begin to turn brown. 



The next operation is to weigh the earth a second time ; 

 and the loss it has sustained will be equal to the weight of 

 the water which has been evaporated. This operation 

 does not determine exactly the weight of water contained 

 in the earth, because one part of it is nearly solidified by 

 its combination with some of the earthy principles, as 

 alumina, the salts, and many other substances, animal 

 and vegetable ; but it ascertains the quantity which served 

 to moisten the earth. In performing experiments upon 

 earths at a high degree of temperature, it is easy to ascer- 

 tain the power which they have of absorbing moisture, 

 and from this some judgment may be formed of their fer- 

 tility. 



As soon as the quantity of free moisture contained in 

 the earth is ascertained, the sample must be bruised in a 

 mortar till it becomes only a collection of small particles. 

 By means of shaking upon a sieve, the gravel and other 

 hard substances, which enter into the composition, may be 

 separated from the other matters, which, having been ren- 

 dered finer, will pass through readily. The coarsest par- 

 ticles should be assayed separately from the others; if 



