264: 



EARTHY PHOSPHATES. 



magneisa, and ammonia. The Baker guano contains 

 as much as 80 per cent., the Jarvis gua.no 33 or 34 per 

 cent, of phosphate of lime ; the latter having, besides, 

 44 per cent, of gypsum. In diffusibility, these guanos, 

 when equally finely powdered, approach nearest to bone- 

 dust: their condition also enables the farmer who wishes 

 to accelerate their action, to convert them most readily 

 into superphosphates (100 parts by weight of Baker 

 guano require 20 to 25 per cent, of concentrated, or 30 

 to 40 per cent, of the lead chamber sulphuric acid). 



The influence of these neutral phosphates upon the 

 produce of a field is generally less marked in the first 

 than in the following years, as it takes a certain time 

 to effect their diffusion through the soil. The speedier 

 or slower manifestation of their action upon a field 

 depends, in a great measure, upon the state of fine- 

 ness of the powder, to which they have been reduced, 

 the greater or less porosity of the soil, the presence in 

 it of decaying matters, and careful tillage ; but, under 

 any circumstances, they require a certain store of sol- 

 uble silicic acid, and of soda and potash in the soil. 



The subjoined table giving the produce obtained, 

 in the years 1847-50, by H. Zenker, at Klein wolmsdorf, 

 in Saxony, shows the difference between guano and 

 bone-dust as regards rapidity and duration of action. 

 In the first year the guano gave the larger produce, 

 which became smaller in each following year ; in the 

 first year the crop from the bone-dust was smaller, but in 

 the succeeding years the increase was most remarkable. 



