404: Jones — Review of Chamberlin' s Groundwork . 



higher density than is actually the case. As Daly has 

 pointed out 26 the extrusive rocks should contain conspic- 

 uous proportions of the metallic alloys of low tempera- 

 ture fusion. Their absence from the visible extrusive 

 rocks implies their absence from whence these rocks 

 come. Either then the magmas are derived from surficial 

 depths or the metals do not constitute even a small por- 

 tion of the earth. But this conclusion is not compatible 

 with meteoritic composition nor with the earth's magnetic 

 properties. 



Furthermore high pressure experiments indicate that 

 density increases so slowly with increased pressure that 

 even at normal temperatures the pressures within the 

 earth could not give to visible rocks the required density. 

 Again transmitted seismic waves imply a concentric 

 arrangement not only of physical state but of material. 



Nor can deductions favoring increase of density by self 

 compression be safely drawn from a consideration of the 

 masses and densities of nearby planets. Chamberlin has 

 stated 27 that as between the Moon, Mars, Venus, and the 

 earth there is "an accelerated rate of increase for each 

 increment of mass/' and that "this clearly implies that 

 their densities arise from their own massiveness." This 

 implication would carry more weight if the densities of 

 the Moon and of Venus were more accurately known. In 

 so far as the densities are determined these, when plotted 

 against masses, do not fall on an increment curve. The 

 earth's density is too low to even fall on a straight line 

 drawn through the Mars and Moon points, much less 

 showing an accelerated density increase. If the Earth, 

 Venus and Mars points are taken as points on an incre- 

 ment curve, then the Moon's density is too low, and if the 

 earth, Venus and Moon points are taken then the density 

 of Mars is too high. The density of Venus is doubtful 

 so if the Earth, Mars and Moon points be taken as points 

 on a curve these three bodies show a decreasing rate of 

 increase of density for each increment of mass rather 

 than an increasing rate. 



To say that "simple pressure experiments are incom- 

 petent to determine the limit of self -compression" 28 and 



26 E. A. Daly : Igneous Eocks and Their Origin, New York, 1914, p. 161. 



27 Jour. Geology, vol. 29, p. 401, 1921. 



28 T. C. Chamberlin : Op. cit., p. 402. 



