PHOSPHOEIC ACID. 3 



oxides of iron, manganese, lead and copper, this body constantly 

 reveals its presence to the expert chemist who makes a special search 

 for it. Its proportions are most often very minute, but that 

 matters little, as plants have a marvellous faculty of freeing from 

 the soil the principles necessary to their development. And let 

 us remark with Bobierre, "how everything hangs on a chain, to 

 explain to us the distribution of phosphoric acid in our crops. Let 

 us go back, in imagination, to the origin of things, to those great 

 natural phenomena, all the traditions in regard to which are in ac- 

 cordance with what geology reveals to us of these gigantic phases. 

 The igneous rocks contain phosphoric acid. The disintegration of 

 these rocks under the combined influence of Vv^ater, air, temperature, 

 and carbonic acid, soon favours the physical divisions of the rock 

 masses. Vegetation develops, vivacious, luxuriant, immense, ac- 

 cumulating at the same time both carbon from the atmosphere — 

 which it is to return as coal to far-off generations — and phosphates 

 which its organs, immersed in a virgin soil, assimilate to abandon 

 one day in a fine state of division on the surface of the soil. And 

 as an energetic, active, incessant medium of this providential dis- 

 tribution, the animal world supervened with its powerful capacity 

 of condensation of principles, rich in phosphorus and in nitrogen. 

 Thus it is that vegetation supplies phosphates clothed in a new dress 

 for the alimentary needs of new individuals. The molecule of phos- 

 phoric acid is no longer the inert crystalline portion of the igneous 

 rock, it is no longer the mineral framew^ork of the plant, it is the 

 osseous substance of the animal, it is both its skeleton and its flesh, 

 its nervous fibre, and its entire being. Our ideas of the organism 

 and of phosphorus are inseparable the one from the other." The 

 beds of the different geological periods all contain fossils, more or less 

 rich in phosphoric acid. The Cambrian yields Licjulides and Dis- 

 cenides, forerunners of the Brachmpods, whose calcareous shells were 

 comparatively rich in phosphoric acid. At a later period vertebrae 

 appear ; first, the Silurian fish, then the saurians of the Carbonifer- 

 ous and Permian, and finally, the birds (Jurassic) and mammals 

 (Trias), the skeletons of which form the principal elements of the 

 accumulation of phosphoric acid. Thus the soil of all formations 

 may contain phosphates, but they are not found in large quantity 

 except in certain formations and under peculiarly favourable circum- 

 stances, which we vaguely perceive, but of which it is impossible 

 to give a really satisfactory explanation. The solution of phosphoric 

 acid by rain water, charged with carbonic acid, traversing the 

 superficial layer of soil covered with vegetation and thus rich in 

 humus, its entrainment into the subsoil, and its accumulation 

 in the subjacent rock, the chemical affinity of which favours its 

 combii.ation — such seems to be the genesis of phosphate deposits. 

 I leeting hme, oxides of iron, and alumina the phosphoric acid solu- 



