380 BOARD OF AGRICULTURE. 



To these amounts should be added the value of the minor con- 

 stituents, which although not adding largely to the sum total, 

 really add something ; as for instance, the sulphate of lime, of 

 which there must necessarily be rather more than twice as much 

 as there is of soluble phosphoric acid, and if the phosphatic mate- 

 rial used contains carbonate of lime, as most frequently occurs, 

 there will be more. This being formed and precipitated in the 

 process of manufacture, is in a state of very minute division, and 

 therefore more readily soluble than the mineral gypsum com- 

 monly sold. So, too, there is usually present more or less of 

 alkaline salts of variable composition and vaMie. 

 * We see, therefore, that one of the superphosphates exceeds in 

 . value (estimated by our scale) the selling price, and several others 

 make a close approach to it. 



"We might with propriety have included among the superphos- 

 phates Wilson's "tobacco grower," since it is neither more nor 

 less than a superphosphate, except that it contained between three 

 and four per cent, of potash. Estimating the soluble and insoluble 

 phosphoric acid and ammonia, by our scale of prices, and leaving 

 out of account the "II pounds of potash contained in one ton, it 

 would come to $35.30. It may appear strange that an article 

 bearing so good a reputation as that, does should show so small a 

 value, but it may be accounted for by the fact that it is mainly a 

 by product of another manufacture, namely Horsford's phosphatic 

 bread preparation, and by reason of this its mechanical and mo- 

 lecular condition is remarkably good, and thus manifests greater 

 immediate efficacy than would naturally be expected from a bare 

 statement of its contents as the result of analysis. 



This brings to view a thought which was presented at some 

 length on a former occasion, namely, that it cannot be justlj'- claimed 

 that analysis will reveal all which is desirable to be known about 

 a manure. It will show with certainty what is in it, but not so 

 certainly about the combinations, or chemical, or mechanical con- 

 dition in which the constituents exist in it, and this is sometimes 

 a matter of importance, for even with regard to mechanical con- 

 dition, which one might suppose could be determined with 

 sufficient accuracy by sight and touch, there may really be a very 

 wide difference between two articles which appear equally well 

 to ordinary inspection. 



Nor is it claimed that the scale of values here adopted is all that 

 is to be desired. From tlie nutna'o of the case np absolute stand- 



