On the Physical Properties of Soit. 



213 



Note A (referred to in page 185). 



On the Employment of the Power of Containing Water in the 

 Examination of the Constituents of a Soil. — Cadet de Gassicourt, 

 in modern times, has proposed what he considers an easj and 

 practicable method for farmers to ascertain with great probability 

 the fertility and constituents of a soil, founded on its power of 

 containing water, and without their having recourse to chemical 

 re-agents a method we cannot omit noticing in detail on this occa- 

 sion, as many agricultural works have already referred to it, with- 

 out however at the same time subjoining any accurate comparative 

 trials of its practicability. We place 400 grammes (that is, a little 

 more than 14 avoirdupois ounces) of earth, previously sifted and 

 dried at 122°, on a filter of which the weight has also been found, 

 and pour over it an equal quantity of water, observing the increase 

 of weight in the moistened earth, and the time the water takes to 

 pass through it : we repeat this experiment four times, and take 

 the average of the whole. In order to obtain the probable fer- 

 tility, we look into the following Table, and ascertain which of the 

 calculations it is that the quantity of absorbed water, and the time 

 of absorption, most nearly approaches : in order to be able to 

 compare these results more nearly with those already given, I in- 

 clude in a column of the Table the power of containing water per 

 cent, as calculated from these data : — 



Quantity of 

 \ ater absorbed 



by 400 

 grammes, or 

 7527 grains. 



Power of con- 

 taining 

 water per 

 cent. 



Time of 

 tlie 

 experiment, 

 in 

 hours. 



Probable Constituents of the Eartli. 



Grammes. 



80 to 90 

 100 , , 110 

 120 130 



120 130 

 180 , , 195 

 180 195 

 240 , , 250 

 320 . , 350 

 325 , , 335 

 350 ,, 360 

 390 ,, 400 



20 to 22 

 25 ,, 27.5 

 30 ,, 32.5 



,,32.5 

 ,,49 

 ,,49 

 ,,62 

 ,,87 

 81.2 83.7 

 87.5 ,, 90.0 

 97.5 100 



3 to 



Almost pure sand, or with very little lime. 



Almost pure sterile limestone. 



Light sandy earth, heath-land, with 



about ith clay. 

 But little fertile, doubtless calcareous. 

 Arid, and when grey probably calcareous. 

 Rather heavy soil, with almost |rds clay. 

 Heavy, and without doubt very fertile. 

 Firm clay soil. 

 Almost pure clay. 

 Marl soil, calcareous sterile clay. 

 Vegetable garden-manure-soil, good to 



use as manure, or to mix with heavy 



soil or sand. 



Let us compare the resul ts of this Table with what has already 

 been said on the power of the several earths to contain water, and 



* Bibliotheque Universelle, section ' Agriculture,* tome J, p. 97. Ge- 

 neve, 1816. 



