ECONOMY OF FARMING. 67 



Here also we are reminded of Professor Schubler's numerous experiments of tliis 

 kind. He found the following results : 



100 parts in weight of dry earth spread on a pane 

 beneath a glass bell, water-tight, absorbed in 

 Kinds of earth. 12 hours, 24 hours, 48 hours, 72 hours, 



(iuiirtz-sand, parts. parts. parts. parts. 



Lime-sand, 2 



Gypsum of earthy form. . . .1 

 Carbonate of hme, in the form of powder, 26 

 Carbonate of magnesia, in powder, 69 



Potters' clay, 21 



Loamy clay, 25 



Pure gray clay, .... 37 



Humic acid, 80 



Plough-land, loam soil, ... 16 



" As to gypsum, we see that it attracts scarcely no water from the air. But it is usu- 

 ally believed that gypsum, employed as a manure, especially promotes vegetation, in 

 that it attracts moisture from the air, which it transmits to plants. Thus, theories 

 which are written down, often fall to nothing when tested by experiment." 



Speaking of the absorption of oxygen from the air, to which acid he attributes an 

 important part in vegetation, he remarks, p. 296, that '' the working over of the soil 

 has this benefit, that thereby new strata of the earth always come in connexion with 

 the air, and thus absorii much oxygen, by which they are more and more fertilized. 

 Other gases also, as carbonic acid, nitrogen, hydrogen, are absorbed." The decrease 

 of the volume of different earths, by being dried. Professor Schubler found to be 

 the following : 



1000 cubic lines 1000 parts by weight 



Kinds of Earth. diminution of diminished there- 



volume in fore in its volume 



auartz sand, .... 0— C. L. 0— 



Potters' clay, . . , 940 " 60 



Loamy clay, .... 911 " 89 



Pure gray clay, ... 817 « 183 



Humic acid, .... 800 " 200 



Carbonate of lime, as powder, 950 '♦ 50 



Plough-land loam soil, . . 880 " 120 



From this table it is evident that the degree of the decrease of the volume of the 

 earth stood in no direct proportion with its power of retaining water." 



" The property of some kinds of the soil, especially marl, by moisture and then by 

 being dried again, to fall into small pieces and become crumbly, is sufficiently explained 

 by the great difference of the decrease of their volumes, which the constituents of 

 the soil undergo, as clay, lime, humus, &c. ; since, be the soil or marl ever so inti- 

 mately mingled, yet their constituent parts always only lie near together. But the 

 particular parts change by the shrinking together, in different proportions, of their 

 volumes, which naturally produces their separation, and soon their decomposition." 



"According to Schubler's experiments (see Sprengel, p. 301) the following are 

 the results as to the capacity of different earths to retain for a longer or shorter time 

 the warmth they have received : 



Po 



Kinds of Earth. 



Limestone sand, .... 



duartz sand, 



Gypsum earth, .... 



Potters' clay, 



Loamy clay 



Pure gray clay, .... 



Ciirbonate of magnesia finely powdered, 

 Carbonate of lime " " 



Humic acid, 



Plough-land loam soil, 



" Hence it appears that the sandy kinds possess tlie orreatest power of retaining 

 warmth, if the earths are compared in equal quantities. Have the sandy soils reached 



