ADMIXTURE OF SOILS. 29 



has been found in all the argillaceous earths in which it has 

 been sought. The fact that they contain potash may be proved, 

 in the clays of the transition and stratified mountains, by simply 

 digesting them with sulphuric acid, by which process alum is 

 formed. Land of the greatest fertility contains argillaceous 

 earths and other disintegrated minerals, with chalk and sand in 

 such a proportion as to give free access to air and moisture/ 



The remarks of Boussingault on this subject are, in my opinion, 

 well worth giving to my reader. &quot; The qualities which we 

 esteem in a workable soil depend almost exclusively upon the 

 mechanical mixture of its elements. We are much less interested 

 in its chemical composition than in this : so that simple wash 

 ing, which shows the relations between the sand and the clay, 

 tells, of itself, much more that is important to us than an elab 

 orate chemical analysis. The quality of an arable soil depends 

 essentially on the association of these two matters. Sand, 

 whether it be siliceous, calcareous, or felspathic, always renders 

 a soil friable, permeable, and loose. It facilitates the access of 

 the air and the drainage of the water ; and its influence is more 

 or less favorable, as it exists in the state of minute subdivision, 

 or in the state of coarse sand or of gravel. Clay possesses physi 

 cal properties entirely opposed to those of sand. United with 

 water, it forms an adhesive, plastic paste, which, once moistened, 

 becomes almost impermeable. With such characters, it will 

 easily be conceived how it is impossible to work to advantage a 

 soil that is entirely argillaceous. The proper character, or, if you 

 will, the quality of soil, depends, then, essentially on the element 

 which predominates in the mixture of sand and clay that composes 

 it ; and between the two extremes, which arc alike unfavorable 

 to vegetation, viz., the completely sandy soil and the unmixed 

 clay, all the other varieties, all the intermediate shades, can bo 

 placed.&quot; * 



An account is given in the Journal of the Agricultural Society 

 of the application of bituminous shale to land, with very bene 

 ficial effects. This shale may be considered as an imperfectly- 

 formed coal, a slaty stone, which is found on the opening of coal 

 quarries, and is generally deemed an indication of the neighbor 

 hood of coal. A quantity of this substance had been thrown out 



* Rural Economy, p. 26G. 

 3* 



