240 EXPERIMENT WITH PHOSPHATIC NODULES. 



No manure gave ... 5 tons 15^ cwt. of bulbs. 



Bone-dust, 184 lb., . ) \ 



Sulphuric acid, 70 lb., . J gav 



Phosphate nodules, 3 cwt., ) . . . 



Sulphuric acid, 168 lb., ' J 



Thus the 3 cwt. of the impure mineral phosphate gave sensi- 

 bly the same weight of bulbs as the four bushels or 184 lb. of 

 bones. It was remarked, however, that the boned turnips 

 came away quicker, and for three months maintained a more rapid 

 growth than the others. Two things are not stated by Mr 

 Cooper, which it would have been desirable to know ; first, the 

 proportion of phosphate of lime which the nodules employed 

 by him contained ; and, second, the relative weights of tops 

 produced by the several patches. 



It is satisfactory, however, to be able to conclude that these 

 mineral phosphates, when prepared by means of sulphuric acid, 

 are really powerfully fertilising substances, and to learn from 

 Mr Cooper that the nodules he employed were purchased at the 

 low price of three shillings a hundredweight. These facts ought 

 not only to stimulate our search for further deposits of such 

 nodules, but to urge practical men to more numerous and more 

 precise experiments with them when found. 



2. Suggestions for comparative experiments with burned limes 

 containing the phosphate of lime in different proportions. 



If limestones or burned limes contain the phosphate in dif- 

 ferent proportions, they ought to produce sensibly different 

 effects upon the land. They ought also, in consequence, to be 

 more or less valuable to the practical farmer. 



The analyses of limestones introduced into the preceding 

 chapter show that they do thus differ. Though probably always 

 present, yet, in some cases, the proportion of phosphate is ex- 

 ceedingly small. Thus, two specimens of magnesian limestone 

 from the county of Durham gave me only 0.07 and 0.015 per 

 cent respectively, while the mountain limestone from Carluke, 

 of which I have already spoken, (p. 226,) contained 1.39 per 

 cent, and, in the burned state, 2.33 per cent. 



