24 Missing Chapters of Geological History. 



rocks being absent in England, and others of more recent date 

 might be made out, but there is more continuity than interrup- 

 tion, in spite of enormous changes, and there has been a 

 frequent but gradual introduction of new species, both of 

 marine and land animals. 



To sum up the result, we may thus recapitulate : — 



There are between the oldest known fossiliferous rocks and 



the upper Silurian rocks 6 physical breaks. 



In the Old Red Sandstone .... I „ 



In the Carboniferous system .... 1 ,, 



Between Carboniferous and Permian . 1 „ 



Between Permian and New Red Sandstone 1 ,, 



In the New Red Sandstone .... 1 „ 



In the Lias 1 ,, 



Between the Oolitic andCretaceous systems 1 „ 



Between the lower and upper Greensand 1 „ 



Between Secondary and Tertiary 1 ,, 



In the Tertiary series 1 „ 



There are thus nine breaks in the Palaeozoic series, four in 

 the Secondary, and one in the Tertiary, besides the breaks be- 

 tween Palaeozoic and Secondary, and Secondary and Tertiary 

 respectively, making in all sixteen important physical breaks 

 in the succession of the strata in England. The number of 

 less important interruptions is very large ; but it would be 

 difficult to estimate them, or to decide, in the present state of 

 knowledge, whether the facts justify the assumption of a break 

 of the nature here described. 



The conclusions to be drawn from the consideration of these 

 facts in geology well deserve careful study. In the first place, 

 there is the general inference, which may be given nearly in the 

 words of Professor Ramsay, that "in cases of superposition of 

 fossiliferous strata, in proportion as the species are more or 

 less continuous, that is to say, as the break in the succession of 

 life is partial or complete, so was the time that elapsed between 

 the close of the lower and the commencement of the upper 

 strata a shorter or a longer interval.'" It is important to note 

 here, that " the break in life may be indicated not only by a 

 difference of species, but yet more importantly by the absence 

 of older and appearance of newer allied or unallied genera." 



It results from this inference, if correct, that " strata only 

 a few yards in thickness, or even the absence of such strata, 

 may serve to indicate a period of time as great as that required 

 for a considerable accumulation of fossiliferous deposits." 



But again we see that a recognition of the importance due 

 to the absence of certain links in the chain — links found per- 

 haps elsewhere — tends to increase enormously the time, already 

 very great, that seems to have been needed for the deposition 



