OL. XX, Second Series. 



ROCHESTER, N. Y., AUGUST, 1859. 



No. 8. 



ON SOME POINTS IN AGSICULTURAL SCIENCE." 



crcii is the unpretending heading of an able and 

 terestiug article in the last number of Sillimaii's 

 ournal, from the pen of Prof. S. "W. Johnson, of 

 ale College, It will be recollected that we have 

 squently alluded to the experiments of Wat and 

 :<i0MPS0N " On the Power of Soils to absorb Ma- 

 ire." That the soil has the power of absorbing 

 ors, has long been known. Hence we bury gar- 

 3nts upon which the fetor of the skunk has 

 len ; and it is said that the Indians sweeten the 

 rcass of the skunk, and render it fit for eating, 

 th© same simple process. Dogs and foxes bury 

 nes and meat in the ground, and afterwards ex- 

 .me them in a state of comparative freedom from 

 ensive odors. But by what means these effects 

 re produced, we had, previous to Way's inves- 

 ations, only very vague conceptions. The ab- 

 bent power of the soil, like that of charcoal, 

 IS referred " to the surface attraction of porous 

 dies." Wat discovered that it was due to the 

 sence in the soil of double silicates. He found 

 it ordinary soils possess the power of separating 

 im solution in water the different earthy and 

 aline substances presented to them in manure. 

 us, when solutions of salts of ammonia, of pot- 

 magnesia, &c., were made to filter slowly 

 ough a bed of dry soil, five or six inches deep, 

 aiiged in a flower-pot, or other suitable vessel, 

 was observed that the liquid which ran through 

 longer contained any of the ammonia or other 

 t employed. The soil had, in some form or 

 ler, retained the alkaline substance, while the 

 ter in which it was previously dissolved passed 

 ■ough. 



[t was also found that the combination between 

 soil and the alkaline substance was rapid, if 

 instantaneous, partaking therefore of the nature 

 the ordinary union between an acid and an alkali. 

 [a the course of his experiments, several differ- 

 ; soils were operated upon, and it was found that 



all soils capable of profitable cultivation possessed 

 the property in question in a greater or less degree. 



These double silicates were found to have a 

 strong attraction for ammonia — lime, soda, or 

 potash silicate being decomposed when ammonia 

 in solution is filtered through the soil — the ammo- 

 nia being retained. But it would appear that the 

 lime silicate alone has the power of attracting am- 

 monia from the air; and hence, perhaps, one of 

 the advantages of liming land. 



These important experiments not only opened 

 up a new field for investigation, but materially 

 affected our views in regard to the action of ma- 

 nures. Thus Wat found that the ammonia-sili- 

 cate was much more soluble in water to which a 

 little common salt had been added than in pure 

 water ; and he suggested that the eifect of salt on 

 some soils might be ascribed not to its furnish- 

 ing chlorine and sodium to plants, but in increas- 

 ing the solubility of ammonia in the soil. In the 

 experiments on wheat, at Eothamstead, Mr. Lawes 

 found that though the increase of the crop was, 

 other things being the same, always in proportion 

 to the quantity of ammonia supplied in manure ; 

 yet the quantity of nitrogen (ammonia) in the in- 

 crease of wheat and straw was far less than the 

 quantity of ammonia supplied in the manure; and 

 therefore concluded that ammonia or its elements 

 was evaporated from the wheat plants during their 

 growth. When Wat made his important discov 

 ery of the formation of ammonia-silicates, he sug- 

 gested that the large quantity of silica found in the 

 straw of wheat and other cereals, was taken up as 

 an ammonia-silicate — the silica being deposited on 

 the straw and the ammonia evaporated into the 

 atmos],>here. Hence the loss of ammonia in grow- 

 ing wheat. 



If the fact of the loss of ammonia in growing 

 wheat was admitted, the celebrated " mineral ma- 

 nure theory" of Liebig fell to the ground; and 

 accordingly, in " Liebig's Reply to Lawea," he 

 pronounced the experiments of Wat, and the 



