220 [Senate 



for the growth of all the crops which may be produced on the land 

 for thousands of years. Yet other chemists dwell on the importance 

 of these substances applied as manures, and direct experiment shows 

 their utility. * Liebig says that " wheat does not flourish in a sandy 

 soil, and that a calcareous soil is also unsuitable for its growth unless 

 mixed with a considerable quantity of clay" — " because these soils 

 do not contain alkalies in sufficient quantity." But Johnston shows 

 not only that excellent wheat crops are reaped from those soils, but 

 that turnips, universally admitted to be finely adapted to sandy land, 

 contain in a single crop of ordinary productiveness, nearly ten times 

 as much potash and soda, as a crop of fifty bushels of wheat with the 

 straw included. The contradictions of chemists on the single article 

 of gypsum alone would perhaps fill a volume. According to Koll- 

 ner, its action depends on the power possessed by lime to form, with 

 the oxygen and carbon of the atmosphere, compounds which are 

 favorable to vegetation ; according to Mayer and Brown, it merely 

 improves the physical properties of the soil ; ^vhile according to Riel, 

 it is an essential constituent of the plant. Hedwig called it the sa- 

 liva or gastric juice of the plant ; Humboldt and Thaer considered 

 it a stimulant ; Chaptal ascribed its action to a supposed power of 

 supplying water f and carbonic acid to plants ; and Davy regarded 

 it as an eessential constituent of plants. J According to Liebig, it 

 fixes the ammonia of the atmosphere ; according to Sprengel, it sup- 

 plies sulphur for the formation of the legumin of leguminous plants ; 

 and according to Dana it merely assists the decomposition of other 

 substances in the soil. 



The question has been much oftener asked than answered, " Who 

 shall decide when doctors disagree 1" If great men, ^who have 

 spent their whole lives in examining such questions, are so much at 

 variance, to what power is the farmer to look, to dissolve the thick 



* It has been asserted by Liebig and others, that the benefit of lime is owing to the 

 potash it contains. Lime has been applied with great success to soils in Western 

 New-York, which contained many broken fragments of limestone. The lime was 

 from localities, where, by the analysis of Dr. Beck, no potash existed. 



f The opinion that gypsum owed its efficacy to the absorbtion of moisture, has been 

 common in this country. H. Davy exposed a portion of gypsum to the air three fog- 

 gy nights, and found it absorbed only a 720th part. Calculation will show that 

 two bushels spread over an acre, would absorb at the same rate, a stratum of moisture 

 only one-millionth of an inch in thickness, or five thousand times thinner than paper. 



I Hlubeck. 



