25 
been elevated within a period geologically modern ; and Mr. 
Darwin states, " that there is little hazard in assuming that 
" this large portion of the earth's crust floats on a sea of 
" molten rock." And it is not so very improbable that the 
two continents of America and Africa, as suggested by 
Professor Jamieson, may not once have been united. The 
north-east shores of Sweden are rising about (according to 
Lyell) four feet vertically per century. In other parts of 
Scandinavia (see Lyell) the coast is now rising ; and so un- 
certain is it that Great Britain is not partaking of this upward 
movement, that in 1833 the British Association had a level 
line measured or laid down from the British Channel to the 
English Channel, under the direction of Professor Whewell.* 
Fissures and joints. Hade in throws. Origin of mineral 
veins. — Professor Phillips, in his quarto volume on the 
Geology of Yorkshire, has devoted one chapter to the 
" Symmetrical structures of Rocks." The thick massive 
beds of sandstone (says he) are irregularly cracked rather 
than fissured, — the limestones are locally cracked, always 
fissured and jointed. The laminated lias clays are regularly 
jointed. Conglomerates of all kinds have little symmetry, 
but are transversed by great fissures. Every sandstone 
quarry, whatever its geological age, is traversed by cracks, 
larger or smaller, and the upper limestone over large tracts 
from Knottingley to Ferrybridge has large openings 15 to 20 
yards in width, into which the subjacent red marl is squeezed 
up, and there is no doubt that with the exception of the 
jointed structure in the very compact crystallised limestones, 
all the above-named cracks or fissures are only the effects of the 
expansion of the crust of the earth. 
* If there be a gradual expansion from within, sea and earth will both 
arise, and a level line would show no change, although the earth might have 
expanded some 100 feet in diameter. The earth portion would probably arise 
more than the water ; but a visible rise of only four feet in the land might be 
caused by 400 feet in diameter of the earth. 
