No 4.] CHEMICAL AND FARM MANURES. 169 



In the above calculations the l)a8is of composition used 

 was, for dried blood, 11 per cent of nitrogen ; for tankage, 

 6 per cent of nitrogen and 5 per cent of available phosphoric 

 acid; for fish, 7.5 per cent of nitrogen and 4 per cent of 

 available phosphoric acid; and for fine-ground bone, 2 per 

 cent of nitrogen and 11 per cent of available phosphoric acid. 



As a general rule, if dissolved phosphate rock containing 

 between 12 and 13 per cent of soluble phosphoric acid can 

 be bought at $15 per ton, that is about the same from the 

 farmer's stand-point as dissolved bone-black at $19.50 per 

 ton ; or, for a rule that will fit all cases, multiply the price 

 of dissolved phosphate roch hy 1.3, and, if the result is above 

 ihejjrice at which dissolved bone-black is offered, then buy the 

 latter; if the result falls below the quotation for dissolved 

 bone-black, then take the fonner. If double superphosphate 

 can be bought at three thnes, or less than three times, the cost 

 of dissolved phosphate rock, then it is usually more economical 

 than the latter. 



Prof. W. P. Brooks (of Amherst). In rising to speak, 

 I wish in the first place to express my most hearty apprecia- 

 tion of the very able paper to which we have listened. It was 

 full of good things, so full that I fear very few of us will be 

 able to carry them all away with us I want to say that in 

 my opinion this paper is one which, to a very unusual degree, 

 will repay careful reading and careful study. It will become 

 available to all of you, and I sincerely hope that you will 

 not conclude that, having heard it, you do not need to pay 

 further attention to it. You will find by reading it with 

 care that there are many hints that will pay you many times 

 over to act upon. 



There are just a few of the points referred to by the essayist 

 to which I wish to refer. You will remember, in the first 

 place, the paper discussed the question of potash, the sources 

 of potash, — wood ashes, cotton-seed hull ashes, nitrate of 

 potash, carbonate of potash and magnesia, were all spoken 

 of. Wood ashes, as you are well aware, are used in the 

 Connecticut valley, where tobacco is grown, more largely, 

 probably, than in almost any other part of our country, and 

 I am convinced, as a result of observation, that they con- 



