368 n. nicxs on the occubrence 02? 



24. On the Occurrence of Phosphates in the Cambrian Rocks. 

 By Henry Hicks, Esq., F.G.S. With an Appendix on the 

 Chemical Analyses of the Rocks, by W. H. Hudleston, Esq., 

 M.A., F.G.S., F.C.S. (Read February 24, 1875.) 



In a paper by the late Dr. Daubeny, F.R.S., in the Quart. Journ. 

 Chemical Society, vol. vii., entitled " On the produce obtained from 

 Barley sown in rocks of various ages," he endeavoured to prove, by 

 experiments made with rocks from different parts of the Cambrian 

 strata of North Wales, that there was an almost entire absence of 

 phosphoric acid in the rocks of that age. Having failed to extract 

 any phosphoric acid from these by direct analysis, he adopted the 

 plan of testing the relative capacity of rocks of various ages to 

 yield this ingredient to the crops which grew in them ; and by this 

 process he calculated that the Cambrian rocks did not in any case 

 contain more than about . 6Q q Q0Q part, some containing only t 0Q * 00u - 

 The rock-specimens examined were taken from the slate-quarries 

 near Bangor, the quarries of Llanberis, and from near Dolgelly, 

 probably Lingula-flags. In addition to these, he experimented 

 also with Skiddaw slate from Cumberland, and with micaceous slate 

 from near Glasgow, and from them obtained only much the same 

 proportions. From these results he was led to infer that the seas in 

 which these deposits had accumulated contained little or no animal 

 life, and that we had here approached the borders at least of the 

 lower limit of organic existence, especially as there seemed in addi- 

 tion to be an almost entire absence of lime in any form. In the 

 last edition of ' Siluria,' these views are prominently brought forward 

 to prove that very few organic remains could ever have existed in 

 the Cambrian strata ; and it is further mentioned that "in subsequent 

 researches Dr. Daubeny could detect no traces of phosphoric acid in. 

 certain specimens from the Longmynd (which fundamental rock of 

 the Silurian region is no more altered than the overlying Silurian 

 strata), whilst the Ludlow rocks contained as much of it as any of 

 the younger fossiliferous rocks on which he experimented"*. 



I have already shown, in papers communicated to the Geological 

 Society, that these views as to the probable absence of life in these 

 early seas have not been supported by subsequent researches in the 

 Cambrian rocks, and that we have evidence now, in the occurrence of 

 zones of fossil remains to the very base of these rocks, that certain 



* Until after this paper was written, I was unaware that Mr. D. Forbes, 

 F.R.S., had published in the Phil. Mag. May 1857, analyses of Silurian and 

 Cambrian Limestones, which showed results very different from those obtained 

 by Dr. Daubeny. He does not give analyses of rocks of so early an age as those 

 referred to by Dr. Daubeny and in the present paper ; but there is one analysis 

 of a limestone, probably of "Menevian" age, at Church Stretton, which gives 

 as much as 056 per cent, of P 2 5 and 63'10 of carbonate of lime. The other 

 analyses include: — Llandeilo Limestone from Dinover Park, Llancleilo, P.,0_- 

 0-56; Bala Limestone, P 2 5 0'16; Dudley Limestone, P 2 5 046. 



