FARMERS' INSTITUTES. 247 



bone at from $30 to i^oO a ton, or as superphosphate, whicli is more soluble, 

 and therefore more beneficial :is a manure. As su[)crphos|)hate is the only 

 concentrated fertilizer that will probahly be used to any uxtent in this State, I 

 especially invite your attention to this manure, first as to its manufacture. 

 Superpiiosphate is made by taking some material rich in i)hos[)hate of lime, 

 such as bones, or spent bone-black from the sugar refineis, or the fossil or rock 

 pho3|iliate, as it is called, from South Carolina, and acting on it with sulphuric 

 acid (oil of vitriol). Mow, in these substances all the phosphate is but very 

 slightly soluble in water. In them three parts of lime are united with one of 

 acid. Jiut when the oil of vitriol is added it unites with two parts of the" 

 lime, forming twu parts of sulphate of lime, which is plaster. This leaves the 

 phosphoric acid united with one part of limo; then it is called superphosphate 

 of lime, and is very soluble iu cold water. The only reason why the acid was 

 added was to change the phosphate into a solul)le form. Then usually there 

 is added sul[)hate of putush, and dried blood from the slaughter-liouse to furnish 

 the necessary amount of nitrogen, and the whole is sent into the market and 

 sold as "superphosphate." 



Let us look a little closer into the form iu which phosphoric acid exists in 

 superphosjihate. There is first the suluble i)ortion of which we liave already 

 spoken. Tiien there is always some bone or bone black that the acid did not 

 act upon, which is called insoluble 2jho,'<phal.e ; and last, some of the soluble 

 phosi)hate is sure to seize on some lime that is near and go back into a form 

 insoluble in water, which is called re verled phosphate. 



The fpiestion naturally ai'ises, how can we tell the value of a fertilizer? A 

 person might say, for example, that he sowed so muny })ounds of su|)erphos- 

 phate on a part of his wheat-field and obtained a certain number of bushels 

 more than where the fertilizer was not applied, and therefore the superphos- 

 j)hate is worth so much. Such a conclu-iion would be cerrect so far as that 

 crop for that year was concerned. But no fact of general application can be 

 deduced from this exjwriment, because of the variation iu the composition of 

 soils and the character of seasons. Judged by this standard, no two persons 

 would agree on what the selling price of a fertilizer should be. The only way 

 to judge of the value — that is the market price — is to see at what price per 

 pound phosphoric acid, potash and nitrogen are selling in the market. With 

 this data we can tell very nearly what the selling price of a fertilizer should be, 

 knowing its composition. During the past season, on the average, soluble 

 phosphoric acid has been selling at 121 ceuts a pound, nitrogen at 20 cents, 

 and potash at five cents a pound. Now, knowing how many pounds there are 

 in a hundred of the fertilizer of these materials, it is very easy to calculate how 

 much a ton of 2,000 pounds is worth in the market. If we could go into the 

 market and buy superphosphates with the same confidence that we are getting 

 a good article as when we purchase cotton cloth or sugar, the fertilizer ques- 

 tion would be very much simplified. But we cannot. Of all the immense 

 number of superphosphates sold comparatively few are worth near the price 

 asked. Many of them are heavily ballasted with sand or ground oyster or clam 

 shells, i^laster, etc. One cannot judge of the value of a fertilizer from its 

 ajjpearance. It may "smell to heaven,"' and seem very "rich,'' and yet be 

 nearly valueless as a manure. A good example of a fraud in this line is 

 Poj)plein's silicated superphosphate. This company Hooded tlie country with 

 samples of their fertilizer, and issued circulars containing extracts from the 

 works of Liebig and other writers as to the necessity of soluble silica for crops 

 — ideas long since exploded. Let us see what their fertilizer for cereals, for 



