COAL MEASURES MENEATH ESSEX. 1 33 



(far greater in those early stages than anything of which we have 

 experience), which was brought to bear upon those gradually rising 

 portions of the crust, which have formed the nuclei of present 

 continents, before their final emergence above the waters of the 

 universal ocean. By a series of sketch maps Professor Dana, of 

 America, attempted years ago to trace the outlines of the growth of 

 the North American continent from the earliest elevation of the 

 Archaean region of the Canadian Dominion ; and if we turn our 

 attentiorf to the European continent, we can trace in a similar way 

 its gradual growth by deposition of later (stratified) formations 

 going on pari />assii with differential movements of tlie lithosphere 

 of this part of the globe, from the earliest elevation of the Archx-an 

 regions of Scandinavia (with Lapland and Finland), continued 

 through the western flank of the British Kles into Brittany ; while 

 another region of earliest elevation probably extended through 

 Auvergne, Central Germany, Bohemia, and Upper Austria. A 

 portion of the present Spanish Peninsula may perhaps have 

 formed a third and minor region of elevation. 



I have dealt with this matter in papers published back in the 

 " eighties " in its relation to the distribution of the younger Red 

 Rocks of Europe (the Permian and the Trias) with the aid of the 

 writings of some leading Continental geologists, added to my own 

 observations in Germany and in Britain. We are thus brought to 

 see that in later Palaeozoic time, that is to say, in the great Carboni- 

 ferous Period, together with the Post-Carboniferous (the Permian or 

 Dyas), while the crust of the globe was still thinner than it is now, 

 the lithosphere must have been in a very unstable condition of 

 equilibrium, and that, as a rule, those broad belts of its surface, 

 which formed the margins of the earliest regions of elevation 

 (being subjected to less hydrostatic pressure than those portions 

 which served as the beds of the deeper oceanic basins), would furnish 

 conditions of greatest instability ; that is to say, conditions most 

 favourable to the relief of the general strain of the lithosphere by up 

 or down movements. Of such a condition of things we have the 

 actual record in the general facies of those formations, which consti- 

 tute the strata of the Carboniferous Period, to the later portion of 

 which our Coal-measures, as a rule, belong. 



The sequence of changes recorded in the rocks of the later 

 PaUeozoic Period, speaking generally, is as follows (beginning with 

 the older strata) : 



