Mineralogy and Geology. 423 



Mr. Austen re£ards the phosphoric acid of the nodules as of animal 

 origin. When the nodules are rubbed down they present a concentric 

 arrangement of parts, resembling bodies formed, like agates, by infil- 

 tration into cavities ; and our colleague points out that, where the casts 

 of bivalve shells and ammonites are filled with matter conlainin 

 phosphate of lime, these forms must have been first inclosed in the 

 sand, that then the proper shelly matter was removed, and finally that 

 the earthy phosphate occupied the place of the hollow. He supposes 

 that the phosphoric acid may have formed part of the coprolitic matter 

 of the time, this matter in part preserved with its original external form, 

 while more frequently it was broken up and the component portions 

 diffused amid the sand and ooze. He also draws attention to the con- 

 ditions to which the beds containing these substances have been ex- 

 posed since their formation, having been covered by thick deposits and 

 having descended to depths beneath the level of the sea, where they 

 were exposed to an elevated temperature corresponding with the depth 

 and the amount of bad heat-conducting bodies above them, so that 

 many chemical changes were effected, and among them a more general 

 diffusion of phosphoric acid in the mass. 



Mr. Nesbit has also communicated to us some remarks on the pres- 

 ence of phosphoric acid in the subordinate members of the cretaceous 

 series. He states that he mentioned to Mr. Paine, in November, 1847, 

 the existence of a large amount of phosphoric acid in a fertile Farn- 

 ham marl, and that he subsequently obtained 28 per cent, of phosphoric 

 acid from portions of this marl, the general mass containing about 2 

 per cent. Nodules from the Maidstone gault also gave him 28 per 

 cent, of phosphoric acid. Other localities are noticed, and as much 

 as 69 per cent, of phosphoric acid is mentioned as contained in a dark 

 red sandstone rock occurring in masses in the upper portion of the 

 lower greensand at Hind Hill. 



Mr. Wiggins has sent us a notice of the fossil bones and coprolitic 

 j substances discovered in the crag of Suffolk, remarking on the value of 



the latter for agricultural purposes, 200 tons of them having been ob- 

 tained from about a rood of ground, — an additional instance of the re- 

 gains of animals and their freces entombed in rocks of different geolog- 

 ical ages becoming available for the growth of existing plants. 



As regards phosphate of lime and its dissemination, which modern 

 researches have shown is much greater, when sufficient quantities of 

 rocks are examined, than appeared from the analyses of the small por- 

 tions usually employed, — a matter of interest when we consider the 

 phosphate of lime required for certain plants, — we should recollect that 

 when free carbonic acid is present in water, the phosphate, like car- 

 bonate of lime, though not to the same amount, is very soluble. Hence, 

 especially when, as^noticed by Mr. Austin, phosphate of lime is dis- 

 seminated in the state of fresh coprolites amid detrital matter, and 

 water containing free carbonic acid is present and can have access to 

 «, the phosphate of lime would be in a condition to be removed and 

 disseminated. Mr. Austen has alluded to the mixture of such bodies 

 with vegetable matter, to the decomposition of which, with animal 

 tatter also, we might look for some, at least, of the carbonic acid that 

 *ouid aid the solution of the phosphate of lime. As in the case of 



