August 12, 1904.] 



SCIENCE. 



213 



a solid globe. The very high specific gravity 

 of the earth's interior as compared with that 

 of the lithosphere, is believed by the author to 

 be due to an increase in density of the ma- 

 terials composing the deeper parts of the 

 earth's interior, due to pressure, and is not, 

 according to him, to be attributed to a dif- 

 ference in character of these materials as is 

 commonly supposed. 



The great continental or epirogenic uplifts 

 above referred to are not to be confused with 

 the comparatively trivial expansions and con-' 

 tractions to which mountain building is due 

 and which are dealt with by Mr. Mellard Eeade 

 in his ' Origin of Mountain Ranges,' as well 

 as in part two of the present work. These 

 latter are local and due to tangential ' creeps ' 

 in the lithosphere and surface rocks, which are 

 accompanied by a lateral transfer of material 

 from one place to another, and result from the 

 uneven heating of great masses of sediment. 

 The gTeat continental movements result from 

 . alteration in volume of certain portions of the 

 earth's crust, unaccompanied except to a minor 

 extent by lateral movement. 



These great movements, moreover, have a 

 very important influence on the secular varia- 

 tion of sea level, since there can be no altera- 

 tion in the contour of that portion of the sur- 

 face which is covered by the ocean without 

 a corresponding change of oceanic beach levels 

 over the whole surface of the globe. 



In the second part of the book, the author 

 enters upon a description of the results of an 

 experimemtal investigation into the forms de- 

 veloped in certain materials by heating and by 

 compression. These are presented for the 

 elucidation of the problem of the origin of 

 mountain ranges, and represent a continua- 

 tion of the results already set forth in the au- 

 thor's former volume on the subject. The 

 materials employed in these experiments were 

 varied in character. At first the action pro- 

 duced by alternately heating and cooling a 

 lead plate, fixed about the edges in a solid 

 framework, was investigated. Anticlinal 

 folds, simple and overturned, were thus de- 

 veloped in the plate, which became thinner 

 in portions of its area owing to the transfer- 

 rence of lead to the site of the fold. 



Subsequently a series of experiments were 

 carried out on the effects of lateral compres- 

 sion on narrow plates of lead alternating with 

 strips of calico and covered by pieces of board, 

 so arranged as to leave a vacant space above 

 the middle of the composite plate. On com- 

 pression anticlinal folds of several types were 

 developed. 



Bars of soap were then compressed in a sim- 

 ilar manner, but could not be made to bend, a 

 fault with slickensided surfaces always devel- 

 oping. Alternate layers of damp sand and of 

 sand mixed with coal dust were then tried, 

 and again the material would not fold, but 

 sheared, developing a double set of sharply de- 

 fined overthrust faults. Layers of moist sand 

 were then alternated with sheets of tea lead 

 and submitted to compression in the same way. 

 In this case the lead prevented the sand shear- 

 ing, but developed a complicated series of over- 

 turned folds to which the sand accommodated 

 itself. 



A series of experiments were then carried 

 out on the circular compression of disks of 

 various materials, with the development of 

 domed folds of many types, some of them 

 showing spiral or screw-like movements, sim- 

 ilar to those described by Mrs. Gordon in her 

 paper on ' The Torsion Striicture of the 

 Dolomites.' 



The third part of the book consists of ' Re- 

 prints, Speculations and Closing Remarks.' 



Among the reprints are the author's well- 

 known papers on the ' Denudation of the Two 

 Americas,' ' The ISTorth Atlantic as a Geo- 

 logical Basin,' and a ' Theory of Slate Struc- 

 ture and Slaty Cleavage.' It also includes 

 chapters on ' Time as a Geological Factor,' 

 and on the bearing of the present investiga- 

 tions in the supposed permanence of ocean 

 basins and continents, on which latter much- 

 debated question the conclusion is reached that 

 ' interchanges of such magnitude have oc- 

 curred in the distribution of the oceans and 

 land masses during geologic time that it would 

 be a misnomer to call them permanent.' 



The book, while containing many interest- 

 ing observations and embodying much re- 

 search, would be improved by a more careful 

 elaboration of the material which it contains. 



