APPENDIX H: LYELL 435 



We shall first advert briefly to many difficulties which formerly 

 appeared insurmountable, but which, in the last forty years, have 

 been partially or entirely removed by the progress of science ; and 

 shall afterwards consider the objections that still remain to the doc- 

 trine of absolute uniformity. 



In the first place, it was necessary for the supporters of this doc- 

 trine to take for granted incalculable periods of time, in order to ex- 

 plain the formation of sedimentary strata by causes now in diurnal 

 action. The time which they required theoretically, is now granted, 

 as it were, or has become absolutely requisite, to account for another 

 class of phenomena brought to light by more recent investigations. 

 It must always have been evident to unbiassed minds, that succes- 

 sive strata, containing, in regular order of superposition, distinct 

 beds of shells and corals, arranged in families as they grow at the 

 bottom of the sea, could only have been formed by slow and insen- 

 sible degrees in a great lapse of ages, yet, until organic remains were 

 minutely examined and specifically determined, it was rarely possible 

 to prove that the series of deposits met with in one country was not 

 formed simultaneously with that found in another. But we are now 

 able to determine, in numerous instances, the relative dates of sedi- 

 mentary rocks in distant regions, and to show, by their organic re- 

 mains, that they were not of contemporary origin, but formed in 

 succession. We often find, that where an interruption in the consecu- 

 tive formations in one district is indicated by a sudden transition 

 from one assemblage of fossil species to another, the chasm is filled 

 up, in some other district, by other important groups of strata. 



The more attentively we study the European continent, the greater 

 we find the extension of the whole series of geological formations, 

 No sooner does the calendar appear to be completed, and the signs 

 of a succession of physical events arranged in chronological order, 

 than we are called upon to intercalate, as it were, some new periods 

 of vast duration. A geologist, whose observations have been confined 

 to England, is accustomed to consider the superior and newer groups 

 of marine strata in our island as modern, and such they are, compara- 

 tively speaking; but when he has travelled through the Italian 

 peninsula and in Sicily, and has seen strata of more recent origin 

 forming mountains several thousand feet high, and has marked a 

 long series both of volcanic and submarine operations, all newer than 

 any of the regular strata which enter largely into the physical struc- 



