158 



ON 



TPIE ORIGIN OF MOUNTAIN RANGES. 



compression involved and not expand at all lioiizontally, but 

 simply become about one-hundredth of an inch higher. Or 

 else the whole expansion would take place in tlie vertical, the 

 block suffering slight deformation, and becoming about tlii-ee- 

 hundredths of an inch higher than it was originally." " As 

 a homely instance of the effect I suppose, may be talccn the 

 case of a loaf of light bread baked in a ' tin.' " (Geol. Mag., 

 vol. X. p. 251). Mr. Reado is thus not the first to draw 

 attention to this effect. Nor (2) when ho comes to work 

 out the results of expansion, does ho take the expansion of 

 volume as " the most potent of all in its geological effects." 

 For in dealing with the effective increase in cubic miles of a 

 given heated area, he disregards vertical expansion, tolling us 

 in a note that "it does not contribute to horizontal displace- 

 ment and consequent permanent ridging tip." He thus lays a 

 good deal of stress on volunio expansion on one page only to 

 abandon it on tho next. 



That however is a minor poiiii). A much more serious 

 criticism is this. In his enthusiasm for his expansion hypo- 

 thesis, he practically neglects to consider whctlior tlie super- 

 induced metamorphism in tho heated rock may not lessen 

 or oven neutralise the effects of mere expansion by heat. 

 What are the views of others on this head ? Dr. Storry 

 Hunt, no mean authority on such a question, says : " The 

 effects of heat and water upon the buried sediments would 

 be condemation, from tho diminution of porosity, and still 

 more from the conversion of tho earthy materials into 

 crystalline species of higher specific gravity, thus causing 

 contraction of tho mass " (quoted in Fhy.sics of the Earth's 

 Crust, p. 202). And Mr. Osmond Fisher inclines to the 

 same 'view; for in a criticism on Captain Hutton's theory, 

 of which Mr. Mellard Roado's is in part a revival, ho says : 

 " But I would go farther, and inquire whether the internal 



