750 



SCIENCE 



[N. S. Vol. XXVI. No. 674 



reviewer the work of Gilbert and "Wood- 

 ward on Lake Bonneville seems of funda- 

 mental suggestion, in considering suborustal 

 fluidity. Consideration of the early stages of 

 the planet without mentioning Winchell, of 

 the cooling at the surface without mentioning 

 Angstrom, of the increase of heat in deep bor- 

 ings without mentioning Darton or Hallock, 

 of the coolness of the Keweenaw copper 

 mines without mentioning Wheeler or Agassiz 

 or Jackson, or Pierce or the reviewer (hinc 

 illse lacrimse!) seems seriously defective. He 

 mentions earthquake vibrations, which are a 

 most promising source of enlightenment, but 

 without mentioning Milne. Two excursuses 

 on the age of the earth and the cause of glacial 

 periods might have been omitted, and might 

 certainly have had more value. The reviewer 

 wonders if Thiene ever saw Joly's paper which 

 he pronounces wholly worthless ! One is led 

 to doubt if he had good command either of 

 English or of mathematics. The caliber of his 

 mathematics may be gauged quite early by his 

 critique of Suckow, taking his own account of 

 it, as the reviewer has not access to Suckow's 

 paper. Suckow " tries to prove that the tem- 

 perature of the earth can not decrease with 

 the square of the distance from the center " 

 (x). " Let C/x" be the drop at the distance x, 

 and the intensity of the heat decrease by du 

 if X increases by dx then " differentiating and 

 noting the peculiar definition of du which 

 eliminates the minus sign customary 



du 20 _ ,, x^ du 



dx x^ ' ' 2 dx 



"Letting du = l°, dx^lOO feet and r" {■=x 

 when a; = radius of earth) "19,608,944, 

 would be 75,398 X 10"° "—or really half this— 

 and, substituting in C/x^ the surface of the 

 earth if it was independent of this heat of the 

 sun, would have a temperature of 196,090° " 

 (or rather half this and helow that at the 

 center). 



Now Thiene criticizes this calculation be- 

 cause " it is dependent upon the unit chosen 

 to measure the earth radius." But while the 

 calculation as Thiene gives it is slightly in 

 error, his criticism is not right. The expres- 

 sion C/x' would vary with the unit chosen for 



X, were it not that G also depends on that unit 

 and is of the same dimensions. One can 

 hardly fairly criticize for lack of mathematical 

 equipment, except that by criticism the author 

 had laid himself open, since this difficult 

 subject requires really a scientific syndicate to 

 handle. We are not surprised, therefore, that 

 in giving account of the results of various 

 authors he has often not shown their bearing 

 one on the other. For instance, he does not 

 show how the theory of a metallic core affects 

 Kelvin's theories, nor is there any discussion 

 of the effect of varying diffusivities in detail, 

 though a table of them is cited from Winkel- 

 mann. The greater the diffusivity the lower 

 the gradient unless there is a constant source. 

 It is clear that if we imagine a large core of 

 metal of high diffusivity covered by a stony 

 rind of relatively low diffusivity we are likely 

 to have the flow of heat, in the latter, reduced 

 to the constant state, the gradient depending 

 not on the time but upon the difference in 

 temperature of the earth and the hot core, 

 which will take billions of years to cool, and 

 also upon the varying diffusivity and thick- 

 nesses of the rocks composing the crust or 

 rind. It is the reviewer's belief that it is more 

 than probable that the flow of heat in the crust 

 early attained this constant condition. 



The author rejects the theory of a gaseous 

 interior, as he rejects the theory that the 

 greater density of the interior is due to 

 pressure. Would it not be better to ask rather 

 to what extent is each factor important? 

 Pressure must have some effect on density. 

 What will it be in view of the various probable 

 or possible changes in temperature and com- 

 position ? 



Without making a sweeping statement 

 at the start as to the gaseous interior 

 of the earth, it is perhaps safe to say in 

 view of what we know of solid solutions 

 and of the gas-like behavior of molecules in 

 dilute solutions, that some of the elements of 

 the earth's interior are in a gaseous condition, 

 and the earth, for them at least, might be 

 likened to a toy balloon, but one in which the 

 gas was so condensed, under such pressure, 

 that one could easier dent a steel ball than it. 

 Under conditions of temperature not easy to 



