their Relation to Geological Formations. 203 



with its most abundant calcic constituent. The same process, it 

 may ho urged, would take place over the shallower areas covered 

 with toraniiuiter-ooze. Admitted, but with this difterence : in 

 the "red-clay" basins foraminifer life evidently approaches 

 zero, whereas in shallower areas it is unquestionably in the 

 ascendant ; therefore any loss of lime the latter areas may 

 sustain through the action of sulphurous acid, would be made 

 up by livinfj Foraniinifera converting the sulphate of lime in 

 the surrounding water into the carbonate comj)Osing their 

 shells. 



Doubtless, whatever the agent may be that produces the 

 "red-clay" deposit, it has contributed more or less to the pro- 

 duction of similar or related formations belonging to different 

 geological periods — though they may be of any colour, depend- 

 ing on the relative amount of their constituents and the nature 

 of their combination. Certain supersilicated rocks (as nova- 

 culite, fuller's earth, chamoisite, &c.) suggest themselves in con- 

 nexion with this idea ; and it is highly probable that many of 

 the glauconites were originally red clays (the residue of forami- 

 nifer-ooze), part of the peroxide of iron of the latter having 

 been reduced to a protoxide by organic matter. I cannot, 

 however, think it is correct to associate the Oldham ian 

 schists (Cambrian) with this idea — that is, "to suspect that 

 they may be organic foi-mations like the modern red clay 

 of the Atlantic and Southern sea, accumulations of the in- 

 soluble ashes of shelled creatures." The thousands of feet 

 of Cambrian schists would require the existence somewhere 

 of vastly more thousands of feet of synchronous limestones. 

 But where are they ? In the recently published paper by 

 Mr. T. Davidson and myself on the T rimer ellidie this ques- 

 tion was briefly discussed *. Failing to ascertain the existence 

 of any limestones of the kind, we made the suggestion that 

 the Cambrian seas were not inhabited by organisms furnished 

 with calcareous skeletons, or they did not contain the ordi- 

 nary amount of calcic constituents. I do not dispute that 



bicarbonate of lime carried into the sea bj' rivere, he naturally concluded 

 that this salt was appropriated by shell-fish. Nevertheless I must still 

 adhere to the opinion I expressed in 1862, that pelagic animals obtain 

 calcic matter from the sulphate of lime contained in the surrounding 

 water. I find that Forchhammer is of opinion " that Testacea decompose 

 the latter substance by means of carbonate of ammonia formed by tneir 

 agency." Bischof thinks that '* it might likewise be decomposed by the 

 organic matter of marine animals into sulphide of calcium, which would 

 be decomposed by the carbonic acid produced by them" (see 'Chemical 

 Geology,' vol. i. p. 180, footnote). 



• Quarterly Journal of the Geological Society, May 1874. 



