314 MANURES AND THEIR APPLICATION. 



by the plough in a state of very good preservation. No tenant- 

 farmer in using half-incli or coarsely crushed bones need hope 

 to reap the benefit of the application during the term of his 

 lease. 



Bones are valuable on account of the phosphate and also of the 

 ammonia they contain. Good bones contain about 50 per cent, 

 of phosphate of lime, and 4| per cent, of ammonia, and should be 

 used in the form of bone meal ground down to as fine a povjder 

 as possible. The expense of extra grinding is far more than 

 compensated by the greater certainty and rapidity with which 

 the manure comes into operation. 



There are two ways of reducing bones to a state of extreme 

 fineness ; the one is by laborious grinding, and the other is by 

 dissolving them with sulphuric acid. Bones, in their natural 

 state, can be only partially dissolved with sulphuric acid, so as 

 to obtain a manure which is dry enough to be spread upon the 

 land, and though manure manufacturers have acquired great 

 skill in the dissolving of bones so as to be able to produce a 

 sample of genuine dissolved bones containing a much higher 

 percentage of soluble phosphate than was formerly able to be 

 obtained, there is no doubt that a large proportion of what is sold 

 as dissolved bones, containing a high average of soluble phos- 

 phate, is really a mixture of bone phosphate with some other 

 phosphate of mineral origin. There is no form of manure so 

 easily sophisticated as dissolved bones, and it is often impossible 

 to tell by analysis or otherwise whether what is called dissolved 

 bones, is dissolved bones, or whether it is in part a dexterous 

 imitation. There is an old prejudice in favour of dissolved 

 bones, rather than any other dissolved phosphate ; and as a high 

 percentage of soluble phosphate is usually demanded, manufac- 

 turers have been forced into the production of a superphosphate, 

 consisting more or less of bone, and have sold it under the name 

 of dissolved bones, in order to satisfy this popular predilec- 

 tion. 



The difference between dissolved bones and other kinds of 

 dissolved phosphate, is that the former contains or ought to con- 

 tain from two or three per cent, of ammonia, while superphos- 

 phates usually contain none at all. It is, therefore, quite unfair 

 to compare the manurial effect of equal weights or of equal values 

 of these two forms of manures. Wliere both phosphates and 

 ammonia are required to enrich the soil, no amount of phosphates 

 will ever compensate for the want of ammonia ; and it is an 

 entire fallacy to suppose that the fine grinding, or dissolving, 

 or any other treatment whatever, of a phosphate, is equivalent 

 to the addition of a certain quantity of ammonia. My own 

 experience, and the experience of all unbiassed experimenters 

 with whose work I am acquainted, show clearly that there is no 



