ORIGIN OF MOUNTAIN RANGES. 569 



i. reade's expansion theory. 



This, the most prominent among alternative theories, was first 

 brought forward in Mr. Reade's book on "Origin of Mountain 

 Ranges." Although I have carefully read all that Mr. Reade 

 has written on the subject, I find it difficult to get a clear idea of 

 his views. But, as I understand it, it is in outline as follows : ( 1 ) 

 Accumulation of sediments off shore and isostatic subsidence of 

 the same. (2) Rise of isogeotherms and heating of the whole 

 mass of sediments and of the underlying crust in proportion to 

 the thickness of the sediments. (3) Expansion of the whole 

 mass in proportion to the rise of temperature. If there were no 

 resistance, this expansion would be in all directions (cubic expan- 

 sion). (4) But since the containing earth will not yield to expan- 

 sion laterally, this lateral expansion is satisfied by folding, and this 

 in turn produces vertical iipszvelling. Thus the whole cubic expansion 

 is converted into vertical expa?/sion, which is therefore three times as 

 great as the linear expansion in any one direction. (5) Eleva- 

 tion would of course anyhow be greatest along the line of thickest 

 sediment ; but this by itself would not be sufficient to produce a 

 mountain. (6) But farther — and here the theory is more obscure 

 — there is a concentration of the effects of expansion, along a 

 comparatively narrow line of thickest sediment, by a flozv of the 

 hydrothermally plastic or even liquid mass beneath, toward this 

 central line and then upward through the parted strata, folding 

 these back on either side and appearing at the crest as the gran- 

 itic or metamorphic axis. (7) In his latest utterances he seems 

 to adopt the view of Reyer, viz., that the uplifted strata slide 

 back down the slope, producing the enormous crumpling so often 

 found, and exposing a wider area of granite axis. (8) From the 

 same liquid mass which lifts the mountain, come also the great 

 fissure eruptions and the volcanoes. 



Mr. Reade makes many experiments to determine the linear 

 expansion of rocks, and he thinks that these experiments show 

 that when cubic expansion is converted into vertical expansion 

 and this again concentrated along a line one-fourth to one-fifth 

 the whole breadth of the expanding mass, it would explain the 



