EXPERIMENT WITH APATITE. 239 



sulphuric acid. The growth of tops, as we should expect, was 

 not so much promoted by the calcined bones as by the farm- 

 yard manure. 



But experiments have also been made with native mineral 

 phosphates, which, in some parts of the world, occur in sufficient 

 abundance to admit of their being used for economical purposes. 

 Thus 



1. With apatite , a comparatively pure native phosphate of 

 lime, Mr Lawes made an experiment in 1844, with the follow- 

 ing effect on the weight of turnip bulbs, per imperial acre : 



No manure gave ... 2 tons 4 cwt. of bulbs. 



Farm -yard manure, 12 tons, . 10 ...15 ... 



Apatite, ground, 3 cwt., . . 3 ... 1 ... 



Do., 200 lb., dissolved in about ) 

 1 cwt. of sulphuric acid, j 



Do., 270 lb., with 104 lb. of acid, 7 ... 3 * 



Here, also, the mineral phosphate also produced a notable 

 increase in the produce. Reduced to powder merely, it could 

 not act either so efficiently or so quickly ; but, when minutely 

 divided by means of sulphuric acid, its sensible effects were 

 largely augmented. Of course, it may be said that the sul- 

 phuric acid employed had a share in the effect produced, and 

 no doubt it may have had, but we are not at present in a 

 condition to say how much ought really to be ascribed to its 

 influence. 



2. With the fossil phosphates of the green sand. Of the 

 occurrence of phosphate nodules and marls in the green sand 

 and in the crag formations, I have already treated in the pre- 

 ceding chapter.f An experiment with these phosphatic nodules, 

 (coprolites, as they were at first called,) dissolved by means of 

 sulphuric acid, was made, in 1846, upon his turnip crop, (variety, 

 white loaf,) in comparison with bones, by Mr Cooper, of Blyth- 

 burgh Lodge, near Langford, with the following results, per 

 imperial acre. The whole field had been manured with farm- 

 yard manure on the clover stubble, preparatory to the wheat- 

 crop of 1845 : 



* Journal of the Royal Agricultural Society, viii., p. 510. 

 t See also Use of Lime in Agriculture, p. 236. 



