Penny Blood: Serial Sensation and Working-Class Entertainment — page 217: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

200 COMPRESSION AND VOLCANIC ACTION. [cu. xv. expansion-coefficient of the rocks which compose it, and the inconsiderableness of the changes of temperature which occur in them, and the cracks thus formed may here come together again, provided no chemical or mechanical sediment has been deposited in them, as is, perhaps, often the case. On the other hand, the forces operate in the earth’s crust during millions of years, and I doubt not that in the circumstances here noticed the cause of the strata being contorted, dislocated and thrown over each other, is to be sought for. This last, perhaps, to judge by the observations I had the opportunity of making on the polar ice, happens far oftener than we commonly suppose, and when it takes place there often occurs no considerable disturbance in the original horizontal position of the stratum. Certainly in most cases the veins filled with foreign minerals, by which the upper strata of the earth in particular are intersected in all directions, derive their origin from similar causes; that is to say, from cracks which have, in consequence of changes of tempera- ture, many times over opened and come together again, pro- vided they were not prevented by the falling in of débris. This has however often taken place, considerable masses of sediments, formed chemically or mechanically, have frequently collected in the cracks, and during the immense duration of geological ages they have hardened and been metamorphosed to solid crystal- line rocks, limestone, quartz, felsite, pegmatite, &c.”’ We find in this extract a theory of the compression of the strata of the earth, proposed by a philosopher of high repute, and no doubt suggested to him by the analogy between ice and rock. It is remarkable however that he does not attribute any part of the compression of ice to the expansion of the water when it freezes in the cracks, and he has missed that part of the analogy on which we insist, which arises from the flotation both of the ice and of the earth’s crust. It is rather to a cause analogous to the expansion of the freezing water, than to variations of temperature im the ice, that we should be disposed to attri- bute such part of the compression as may possibly be connected with the solidification of fluid rock in chasms, It will be noticed 1 s¢The Arctic Voyages of Adolf Erik Nordenskidld,” 1858—1879. London, Macmillan, 1879, p. 239. : COMI1CHOOOKS.EO