BOOK NOTICES. 



The Origin of Mountain Ranges, considered Experimentally^ Struc- 

 turally^ Dynamically^ and in Relation to their Geological History. 

 By T. Meilard Reade, C.E., F.G.S., F.R.I.B.A. 1886, London. 

 8vo, xviii and 359 pp. and xlii plates. 



The well-known ex-President of the Liverpool Geological Society 

 must be congratulated on the boldness of conception and thorough- 

 ness of treatment evinced in this his latest contribution to dynamical 

 geology. He brings to bear upon this much-vexed problem, or series 

 of problems, the experience of a civil engineer as well as the 

 observation of a geologist, and applies the test of numbers to his 

 speculations whenever such a check is possible. 



The author does not enter very fully into the theories held by most 

 writers on the subject of mountain ranges. For a good historical 

 review of the question we may consult Professor Heim's great work 

 Mechanismus der Gebirgsbildung, which is also the best exponent of 

 the current theory ascribing the phenomena of mountain-building to 

 lateral crushing of the earth's crust, caused by the secular contraction 

 of the interior. The inner portion of the globe is constantly losing 

 heat and therefore contracting, while the exterior probably suffers 

 little or no diminution of temperature. Accordingly the interior of 

 the earth must shrink away from the crust, and the weight of the latter 

 will produce in it enormous tangential or lateral thrusts, resulting in 

 local yielding by compression, folding, and upheaval. Mr. Mellard 

 Reade regards this theory as inadequate to explain the appearances 

 seen in mountain ranges, and offers an entirely different hypothesis. 



He begins by pointing out the variabihty of temperature actually 

 observed in the earth's crust. The rise of temperature with increasing 

 depth varies from 1° F. in 28-1 feet to i' in 157*2 feet, and there is 

 eveiy reason to suppose that the rate at any given spot is subject to 

 variation. Assuming an average rise of F. for every 60 feet, the 

 temperature at a depth of 30 miles would probably be approaching 

 the melting point of surface rocks ; but owing to the immense 

 pressure the rocks would not be fused. In supposing the globe to 

 be solid throughout, the author is in accord with the physicists and, 

 perhaps, the majority of geologists. He, however, allows to the 

 rocks at this and greater depths that power of slowly changing form 

 or 'flowing' under unequal strains which has been so much discussed 

 under the name of 'plasticity.' 



After some experiments on sheets of metal and blocks of stone, 

 showing that variations of temperature may produce permanent 

 deformations, we come, in Chapters V and VI, to a consideration of 

 the principal geological phenomena associated with mountain ranges. 



Naturalist, 



