Ixxxii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



when there had been no pumping at the large breweries in London 

 from the deep wells on Sunday, Dr. Lyon Play fair remarks that this 

 would give about twenty miles for filtration through the chalk to the 

 deep wells in London, for so much water as may be supplied from the 

 direction of Watford. 



The agricultural importance of phosphate of lime has of late years 

 caused more search to be made for this substance than formerly, 

 though its occurrence as a component part of certain organic remains 

 and of some rocks has been long known. Mr. Paine, of Farnham, 

 having pointed out that certain beds contained phosphate of lime in 

 sufficient abundance to render them of much agricultural value, our 

 colleague, Mr. iVusten, was induced to investigate the mode of occur- 

 rence of the phosphate of lime in his own neighbourhood, that of 

 Guildford. He found that the phosphate of lime nodules are abun- 

 dant in the upper greensand. They also occur in the gault, in two 

 distinct beds, remarkably persistent in the district. In describing 

 the position of these beds, Mr. Austen takes occasion to point out 

 the inaccuracy of the published geological maps and sections of the 

 district, calling attention to the beds of very different parts of the 

 cretaceous series which are brought up along the escarpment of the 

 North Down range. Having ascertained the facts connected with 

 the layers of phosphate of lime nodules in the vicinity of Guildford, 

 Mr. Austen examined the neighbourhood of Farnham, and found the 

 component parts of the cretaceous series the same as near Guildford, 

 with the exception that sandstones, occasionally cherty, represent near 

 Farnham the firestone on the eastward and the malm rock on the 

 west, differing however from them in containing scarcely any car- 

 bonate of lime. This Mr. Austen infers to have happened from a 

 stream of water, having a course somewhat north and south, drifting 

 rather coarse materials with little calcareous matter in this locality. 



Mr. Austen regards the phosphoric acid of the nodules as of animal 

 origin. When the nodules are rubbed down they present a concen- 

 tric arrangement of parts, resembling bodies formed, like agates, by 

 infiltration into cavities ; and our colleague points out that, where 

 the casts of bivalve shells and ammonites are filled with matter con- 

 taining phosphnlc 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 conditions to which the beds containing these 

 substances h^ve been exposed 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 tem- 

 perature 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. 



