PHOSPHATES IN THE CAMBRIAN ROCKS. 



369 



forms of animal life did exist, and in great abundance, in those early 

 seas. It seemed questionable therefore whether Dr. Daubeny's results 

 as to the absence of phosphoric acid from some of these rocks could 

 be relied upon as in any way indicative of the general condition of 

 the Cambrian rocks. To test this I recently made analyses of rocks 

 from different portions of the Cambrian strata, selecting some beds 

 which were known to contain certain forms only of organic remains, 

 others in which different forms occurred together, and some which 

 hitherto had proved to be unfossiliferous. 



The results obtained tend to show that although some portions 

 of the Cambrian rocks, like some series in comparatively recent for- 

 mations, do not contain more than a mere trace of phosphoric acid, 

 yet there are other portions of the strata, both underlying and inter- 

 stratified with these beds, which give evidence of the presence of 

 this ingredient in considerable quantity, it being equal in amount in 

 some cases to that found in the very richest of the more recent de- 

 posits. It is evident, therefore, that the conclusions arrived at 

 by Dr. Daubeny, and supported by so great an authority as Sir 

 R. Murchison, are entirely fallacious when applied to the whole 

 Cambrian epoch, and that they can now only be accepted for 

 those special portions of the strata examined by him. The follow- 

 ing analyses are sufficient to illustrate these facts, as they include 

 rock-specimens from the very base of the Longmynd (or Harlech) 

 group to the top of the Arenig group. Several of these analyses 

 were made for me by my friends, Mr. Hudleston, P.C.S., and Mr. 

 J. Hughes, F.C.S. 



1. Lower red beds (Longmynd group) 



with Lingulella primceva. 



2. Grey flaggy and purple sandstones, 



unfossiliferous (Longmynd 



group). 



3. Grey flaggy beds (Longmynd group) 



with Trilobites (these beds con- 

 tain a considerable amount of 

 carbonate of lime). 



4. Grey flags (junction of Longmynd 



group with Menevian group) 

 containing fossils sparingly (car- 

 bonate of lime in considerable 

 quantity). 



5. Grey flags, very calcareous-looking , 



(Menevian group), with abun- 

 dance of Trilobites, but only a few 

 other fossils (carbonate of lime 

 as much as 50 per cent, in many 

 parts). 



6. Dark grey and light blue flags (Me- ^ 



nevian Group) with Paradoxides \ 

 Davidis and other large Trilo- }■ 

 bites (carbonate of lime in some 

 parts over 42 percent.). 



7. The same bed, but from another 



part. 



}l 



P 2 5 per cent. 

 0-30 



A trace only. 

 1-50 



0-50 



From 2-00 to 4-00, in 

 proportion to the 

 amount of fossils 

 present. 



From 2-36 to 3-00. 

 1-52 



H. Hicks. 

 H. Hicks. 



H. Hicks. 

 H. Hicks. 



H. Hicks. 



J. Hughes. 



W. H. Hudles- 

 ton. 

 2c2 



