326 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



and about 19 per cent, of mineral matter. 13 A, May 14, 



1870,208. 



SOURCE OF MINERAL PHOSPHATES. 



The source of phosphatic manures, such as are found in the 

 mineral form in various deposits, is a subject that has attract- 

 ed much attention on the part of chemists and agriculturists. 

 Of course, as regards guano, the phosphoric acid is readily 

 referable to the excrement and offal of sea-fowl. Certain gua- 

 no, such as Sombrerite, is derived from the action of water 

 on this matter, and the subjacent calcareous coral rocks. It 

 is thought that much of the palaeozoic phosphatic rocks may 

 have been produced in this way ; at any rate, those which 

 have been formed subsequent to the evolution of terrestrial 

 and vertebrate animals. There are, however, many beds the 

 origin of which can not be referred to any of the causes just 

 mentioned. Professor Dyer, in an article on this subject in 

 JVatwe, suggests the same view that was presented at the 

 late meeting of the American Association by Professor Kerr, 

 namely, that the brachiopods may have supplied a large per- 

 centage, the recent Lingula, as is well known, having over 

 eighty per cent, of phosphate of lime in the mineral ingredi- 

 ent of its shell. In fact, he is of the opinion that the large 

 quantities of phosphate of lime in the Laurentian and Siluri- 

 an, as well as in the Devonian and carboniferous strata, are 

 derived from this source. In the mesozoic and tertiary stra- 

 ta, instead of finding the mineral phosphate in veins and beds, 

 it occurs mostly in the form of nodules. Mr. Dyer coincides 

 with the hypothesis previously presented by Mr. Lankester, 

 based upon the property possessed by clay of detaching phos- 

 phate of lime from its solution in carbonated water. The 

 nodules in question are believed to be bits of clay, which have 

 been imbedded with great quantities of bones, as perhaps, 

 also, with sea-weed, from which, by the intervention of gas- 

 charged water, they have extracted the phosphate. Hence 

 the almost invariable occurrence of beds of phosphatic nod- 

 ules near argillaceous strata. 



This same view has been used to explain the origin of the 

 phosphatic nodule beds which have lately been detected in 

 immense extent in the vicinity of the city of Charleston, 

 forming a mineral fertilizer which is coming into very ex- 



