278 The Phosphates used in Agriculture. 



This proves to us that a great amount of phosphates has 

 been diffused through the Upper Green Sand formations, may-be 

 by the accumulated excrement of myriads of fish and large rep- 

 tiles which inhabited this country at the remote geological 

 periods to which these formations belong. 



I have since analyzed many other sedimentary rocks and 

 fossils, in order to discover whether they contained any notable 

 quantity of phosphate of lime, but rarely found more than one 

 or two per cent., frequently a mere trace only. However, there 

 exist, doubtless, other sources of phosphate yet to be dis- 

 covered. 



If we admit that the mineral phosphate Sombrerite and that 

 of Monk Island be similar minerals, and have been derived, by 

 some unknown geological process, from guano; if we admit, more- 

 over, that the coprolites found in Cambridge and Suffolk are, like 

 those of the Coal and Lias formations, true fossil excrements, 

 mixed here and there with bone ; and, thirdly, if we admit that 

 the other numerous and above-named fossils (wood, sponges, 

 polyps, etc.) fossilized by phosphate of lime, be the result of 

 an impregnation of organic substances by the excrementitious 

 matter of animals now extinct, what a splendid example we 

 have here of applied palaeontology. For since agricultural 

 chemistry began its rapid development, all these " fossil excre- 

 ments " have become valuable as a means of aiding us to keep 

 up the fertility of our soils, to increase our wheat crops, and to 

 have an abundant and cheap supply of bread. We are thus 

 tempted to class all phosphates used in agriculture, including 

 bones, bone- ash, etc., as derived from organized beings that 

 have once flourished upon our globe. 



But we have another source of phosphate of lime in the 

 coarse variety of apatite of Estrcmadura, which appears to have 

 had no connection with organized beings of any description, 

 and cannot be considered as a fossil. The Estremadura phos- 

 phate met with in commerce is the mineral apatite in the massive 

 form ; it is abundant in Spain, and may bo in other countries 

 also, but up to the present time it does not appear to be so 

 plentiful as the other phosphates mentioned in this paper. 

 However, it is of all known substances found in nature that 

 which contains the most, phosphate of lime, the per-centage of 

 which in tho commercial specimens averages from 85 to 87 per 

 cent., and in absolutely pure specimens as much as 92. 



The remaining phosphates used in agriculture are bones, 

 bone-ash, and animal charcoal. The two latter are merely burnt 

 bone. Bones contain the peculiar phosphato known as " bone- 

 earth/' equivalent to about 56 per cent, of ordinary tribasic 

 phosphato of lime. When ground, they often becomo mixed 

 with silica and other impurities. Enormous cargoes of ox- 



