FACTS ABOUT NITRATE OF SODA. 79 



cobs, yet these results have been obtained at different times 

 and by different parties, and therefore have no comparative 

 value, because our modes of inquiry are still imperfect, and 

 success depends a great deal upon the skill of the investi- 

 gator. 



There has been some discussion here to-day in regard to 

 the effect of the use of nitrate of soda, to which I wish to 

 add a few facts which may be of interest ; for the importance 

 of nitrate of soda as a source of nitrogen for plant-growth 

 is daily more recognized in Europe as well as in this coun- 

 try; nitrate of soda furnishing nitrogen in the best form 

 for assimilation, at least so far as actual experiments demon- 

 strate ; and, besides being a plant-feeder, it is a distributer 

 of plant-food, it aids in the diffusion of other articles of 

 plant-food through the body of the soil. An instance of 

 that kind came lately under my observation in a case where 

 several hundred pounds of super-phosphate had been applied 

 to the soil. The drainage was tested, coming from that soil 

 afterwards, and it showed no trace of phosphoric acid : in 

 other words, the phosphoric acid had been entirely retained. 

 But in treating the same soil subsequently with nitrate of 

 soda, and repeating the test in regard to the di-ainage-waters 

 passing through, I found phosphoric acid in the drainage- 

 waters. For these reasons, chemists are in the habit of 

 calling it a chemical plough doing the mechanical work. 



I take the liberty of referring to the question discussed of 

 chemical fertilizers, and their action on the soil. There is, 

 undoubtedly, a specific action of agricultural soil in various 

 descriptions of chemical fertilizers, modifying their compo- 

 sition, and controlling to a large degree their action. If it 

 is to be recognized as an established fact that the form in 

 which plant-food is presented for the absorption of soil 

 affects the growth of the plant, it is of the utmost im- 

 portance to know what changes a fertilizer undergoes by 

 being mixed with the soil. Changes are taldng place which 

 no inspection on general chemical principles would entitle 

 us to assume. To illustrate this point, I will state two 

 observations of my own. I took, in one case, sulphate of 

 lime (common gypsum), and brought it in contact with mag- 

 nesia limestone, or dolomitic limestone, frequently found in 

 our soils as a detritus, broken up, and placed this mixture 



