" movements, different from the agitation of currents or 
" the tide." p. 145. 
On the close of the primary period he says again, 
" There is almost a total absence of proof in the mineral 
" composition and organic remains of the primary strata of 
" the contemporary existence of dry land, for all the early 
" periods, at least, the absence of land plants, and the non- 
" occurrence of conglomerates, seem to justify a doubt 
" w hether the sea of that period was subject to anything of 
" the nature of land flood or littoral agitation. In the slate 
" and Silurian systems the marks of agitation in the sea 
" become more distinct, and from land plants in the 
" grauwacke rocks of the Rhine, and from North Devon, 
" the proof of upraised land is conclusive" p. 146. " There is 
" nothing to contradict the assumption that till the close of 
" the primary period nearly all the strata of the British Isles 
" and the continent of Europe were covered by the sea in 
" which they were formed, and it is doubted whether any 
" certain proof can be shown that any part of the European 
" region was subjected to any great displacement during the 
" primary period." 
If, therefore, at this early period of the earth's history, 
there had been as yet no elevation of land or breakage of its 
crust, the pressure upon the internal and central parts of the 
globe must have been at its maximum. 
The density of the planet Mercury is 2,585, while that of 
the earth at the present time is 1,000, therefore that of Mer- 
cury is two-and-a-half times that of the earth. It may be, 
however, that at the end of the primary period the densities 
of both planets were nearly equal, and therefore, according 
to Kepler's laws, their orbits could not have been very dis- 
similar. 
The primary strata, above the gneiss and mica schist, 
contain marine fossils, proving their aqueous origin ; these 
