TRANSACTIONS Ol'' THK SECTIONS. 73 



fossible shifting of the earth's axis might have on our estimate of geological time, 

 shall return to the phraseology whose amendment seems advisable. 



The confusion which exists is well illustrated in a remark by an eminent Avriter 

 to the effect that the progress of geological research tends to prove the " continuity 

 of geological time." The phrase in itself involves an absurdity ; but what is meant 

 is, that the successive so-called formations pass into each other by imperceptible 

 gradation, and that, as time goes on, we shall be more and more able to intercalate 

 strata so as to present a continuous scale of animal and vegetable forms. This is 

 one out of many samples of the extreme length to which the thirst for strict 

 cori'elation may go. We find in Murcliison's writings and elsewhere pointed pro^ 

 tests against the succession of strata in one district being held to rule that in other 

 districts ; but these are rather concessions wrung from their author by the pressure 

 of particular instances than acknowledgments of a rule applicable to contiguous 

 and to distinct localities alike. I could not perhaps take a better example than the 

 strata which contain the remains of the fossil Equidcc. If we arrange the fossils in 

 any series representing the modification of particular structures, or averaging the 

 modifications of all the structures, we shall find that the terms of the series are met 

 with, now in Europe, now in America ; yet no one would venture to intercalate 

 the European in the American Tertiary series so as to square the geological record 

 with an assumed zoological standard. The notion of gi-adations, the extreme view 

 of correlations, has led to results which are, to put it mildly, of doubtful value. 

 Yet it was a natural result of the work of Cuvier and other palaeontologists among 

 the Mesozoic and Eocene fossiliferous deposits. The statistical method invented 

 by Lyell is simply a mode of gradations. Intercalation of strata is therefore a 

 siu'vival from an earlier stage of the science, and can-ies with it a distinct echo of 

 the catastrophic notion that strata were formed simultaneously and generally over 

 the earth's surface, if not universally. 



The geological record has been compared to a volume of which pages have 

 here and there disappeared ; and the incompleteness of the record has been in- 

 ferred from the frequency of pronounced gaps in the succession of strata. Of these 

 gaps, these unconformities. Prof. Ramsay has shown the importance by demon- 

 strating that they represent the lapse of unknown, but varj'ing, and in all cases 

 considerable periods of time. The intercalation of strata, assumed to fill up the 

 gap, and hereby to give symmetry to systematic classifications, can only be done by 

 an appeal to the statistical method, a fauna containing forms characteristic of higher 

 and lower beds being assumed to represent an intermediate point in time, whereas 

 it might be equally well claimed as representing an intermediate area in space, and 

 as being possibly representative of the whole gap and of some of the strata above 

 and below it. 



The definition of a formation as representing a certain period of time, still re- 

 peated with various modifications, is to blame for this and several other cm-iosities 

 of procedure. But the climax of symmetrical adjustments is reached when we find 

 " natural groups " established — when, in other words, an attempt is made to show a 

 regular periodicity of plienomena in Geology. Dawson proposed a quaternary, 

 Hull a ternary classification — to neither of which should I now refer, but that tlie 

 deserved estimation of these writers is apt to perpetuate what seems to be an unsafe 

 view of geological succession. 



Hull's arrangement has the merit, by force of its simplicity, of bringing the 

 A'ainness of the attempt into prominence. Dawson has complicated his classification 

 so as to render it impracticable. A natural group of strata, one in which elevation, 

 deep depression, elevation, record themselves in rocks so as to establish geological 

 cycles, implies several things for which we have no evidence. Most important of 

 all, it implies that the events above noted should recur in every area in the same 

 order, that they should recur at equal intervals of time, and therefore yield equal 

 masses of strata, and, above all, that the superior and inferior limits of each natiu'al 

 and conterminous group should consist of a mass of similar strata, one portion of 

 which shall belong to the earlier, the other to the later group. Here then we have 

 implied, not catastrophic simplicity as regards the strata, but something very like 

 it as regards the subterranean forces. 



Mr. Hull has not, however, been able to surrender himself wholly to his specula- 



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