Clarence King — Age of the Earth. 



The following analysis is by Gr. "W". Hawes :* 



Silica - 53-13 



Alumina 13*74 



Ferrous oxide . . 9*10 



Ferric oxide 1*08 



Manganous oxide 0'43 



Lime .__ 9-47 



Magnesia 8*58 



Soda 2-30 



Potash 1-03 



Io-nition 0-90 



99-76 



Astronomical and geodetic requirements make necessary 

 that density should proceed downward in shells of successively 

 greater value, but the surface density is 2*75 and the mean 

 density of the whole earth is not twice that of diabase, whence 

 it appears that no probable chemical distribution of material 

 could result in a surface couche of '05 of radius having a 

 greater specific gravity than 3 # to 3*3. 



Waltershausenf in his interesting scheme of chemical distri- 

 bution attempts to account for the augmentation of density 

 chiefly by the increase of the heavy bases, but leaves the 

 whole surface tenth of radius in silicates. Eruptions of alka- 

 line earths or metals are unknown, in fact, with the exception 

 of carbonates of superficial origin the whole visible body 

 of the crust is of silicates, and the earliest rocks are seen to 

 be made of the debris of still older ones. All that can be 

 said is that there is absolutely no known reason why the surface 

 tenth of radius may not be of silicates, nor why specific material 

 of widely different thermal properties from diabase should be 

 postulated. 



The two principal conditions within the interior of the earth 

 upon which physical state and all purely physical reactions of 

 the specific materials depend, are the distributions from center 

 to surface of pressure and heat. Secular or sudden variations 

 of either or both have the power, if carried sufficiently far, to 

 disturb chemical and physical equilibrium and produce changes 

 of volume, rigidity, viscosity, and conductivity, as well as changes 

 of state from liquidity to solidity, and the reverse. Before 

 proceeding to consider in detail some of the results of heat 

 and pressure as existing in the surface '05 of radius, it is desir- 

 able to glance at the relations of these two great antagonistic 



* This Journal, III, vol. ix. 



f '• Rocks of Sicily and Iceland." 



