Notices respecting New Books. 215 



pression. The mean rise of temperature o£ the whole sedimentary 

 mass is half the total rise of the lowest beds." (P. 326.) 



The author then goes on to show that at a certain depth the 

 " cubical expansion " of the mass must cause the heated though 

 still solid materials to actually flow, and in so doing they will pene- 

 trate along the lines of least resistance, giving rise to the gneissic 

 axial cores so constantly exhibited in all great mountain-chains. 

 The actual transfer of this flowing material adds corsiderably to the 

 solidity and the consequent permanency of mountain-ranges. 



That this rise of temperature in the lower portions of a sedi- 

 mentary mass is competent to produce the results he ascribes to 

 it, the author illustrates by many ingenious experiments, and en- 

 forces by very cogent reasoning. He shows that flat masses of 

 lead, stone, and other material ridge up during heating in their 

 centre if their edges be not free to move outwards ; and he further 

 insists upon a consideration which has not hitherto received the 

 attention which it deserves, namely, that the effects of repeated 

 heating and cooling are to a great extent cumulative. A local in- 

 crease of temperature causes expansion ; but in the subsequent fall 

 of temperature, the contraction, or drawing back of the particles is 

 very partial, and thus the changes all work towards the same end. 

 This principle is illustrated by a number of ingenious experiments, 

 and it is argued that in the corrugation of strata we have illustrated 

 the results of accumulations o2 small effects from simple causes. 



Wherever it is possible, the author endeavours to test his own 

 results and those of others by calculations based on data obtained 

 by actual experiment. He has determined the coefficients of ex- 

 pansion of a number of sandstones, marbles, slates, and granites, 

 and the results of these experiments show a very satisfactory agree- 

 ment with those previously published by Adie and Totten. The 

 mean of the whole of his results is a linear expansion of 2*77 feet 

 per mile for every 100° Fahr. This the author points out is equal 

 to about 8*25 feet of cubic expansion ; that is to say, the surface of 

 a cubic mile of rock, if the base and sides were not free to move, 

 would be raised, not 2-75 feet, but 8*25 by a rise of temperature of 

 100° F. In a mass of rock 500 miles square and 20 miles thick — 

 one which would equal only the gj^th part of the bulk of the 

 globe — an increase of 1000° F., or, what would amount to nearly 

 the same thing, a series of alternations in temperature amounting 

 to 1000°, would, it is calculated, cause an expansion of no less than 

 52,135 cubic miles ! 



The latter part of the work before us is occupied by descriptions 

 of varieties of mountain-structure, and an explanation of the 

 manner in which these may be accounted for on the author's 

 theory, as outlined above. Incidentally, many important geological 

 problems are discussed, such as the origin of cleavage, foliation 

 and jointing, the causes of ordinary and reversed faulting, the 

 significance of the "fan-structure," the connection between vol- 

 canic activity and mountain-building, the time required for the 

 formation of mountain-chains, the cause of earthquakes and earth- 



