IMPERFECTION OF GEOLOGICAL RECORD 277 



the palaeozoic and secondary periods, neither continents 

 nor continental islands existed where our oceans now 

 extend ; for had they existed there, palaeozoic and 

 secondary formations would in all probability have 

 been accumulated from sediment derived from their 

 wear and tear ; and would have been at least partially 

 upheaved by the oscillations of level, which we may 

 fairly conclude must have intervened during these 

 enormously long periods. If then we may infer any- 

 thing from these facts, we may infer that where our 

 oceans now extend, oceans have extended from the 

 remotest period of which we have any record ; and on 

 the other hand, that where continents now exist, large 

 tracts of land have existed, subjected no doubt to great 

 oscillations of level, since the earliest silurian period. 

 The coloured map appended to my volume on Coral 

 Reefs, led me to conclude that the great oceans are 

 still mainly areas of subsidence, the great archipelagoes 

 still areas of oscillations of level, and the continent 

 areas of elevation. But have we any right to assume 

 that things have thus remained from the beginning 

 of this world? Our continents seem to have been 

 formed by a preponderance, during many oscillations 

 of level, of the force of elevation ; but may not the 

 areas of preponderant movement have changed in thf 

 lapse of ages? At a period immeasurably antecedt 

 to the silurian epoch, continents may have existed 

 where oceans are now spread out ; and clear and open 

 oceans may have existed where our continents now 

 stand. Nor should we be justified in assuming that if, 

 for instance, the bed of the Pacific Ocean were now 

 converted into a continent, we should there find forma- 

 tions older than the silurian strata, supposing such to 

 have been formerly deposited ; for it might well happen 

 that strata which had subsided some miles nearer to 

 the centre of the earth, and which had been pressed 

 on by an enormous weight of superincumbent water, 

 might have undergone far more metamorphic action 

 than strata which have always remained nearer to the 

 surface. The immense areas in some parts of the 



