450 L, Scemann on the Unity of Geological 



becoming solid while the interior is yet liquid, the natural con- 

 traction of this portion is prevented, and from this necessarily re- 

 sult vacant spaces in the mass, which are afterwards compressed 

 by the action of the hammer. In calculating from the dififerences 

 in density the volume of the vacant spaces thus produced, we find 

 for iron a contraction of O'O'ZS; for nickel 0*045 ; for aluminum 

 0'041 ; for copper 0*011 ; for gold 0*005 ; while the contraction of 

 the earth necessary to absorb the whole atmosphere, would be 

 only 0*004. From this it results that an ingot of gold, the most 

 solid obtained by the fusion of a metal, contains more vacant 

 space in proportion to its volume than would be required in the 

 globe for the absorption of its gaseous envelope ; it is scarcely pos- 

 sible that any crystalline rock should be wanting in this slight 

 degree of porosity. 



From the preceding considerations, the successive absorption of 

 the air and water by the solid portions of the globe, becomes in 

 the highest degree probable, and we may conclude that our earth 

 will one day present that same total absence of ocean and atmos- 

 phere which we now remark in the moon. It is evident that this 

 progress of the waters towards the earth's centre must have long 

 been in operation, and it becomes interesting to consider the 

 effect which this must have had upon the level of the ocean. Let 

 us suppose that the rocks near to the surface of the earth contain 

 one hundredth of water, a proportion which from the above calcu- 

 lation will not be regarded as excessive, and that the water more- 

 over does not exist in this proportion at a depth beyond that at 

 which the terrestrial heat equals 100 degrees centigrade. If we 

 take the augmentation of heat in descending to be one degree for 

 thirty-three meters, this will give a depth of about 3000 meters, 

 while one part of water by weight in one hundred parts of a rock 

 whose density is equal to 2*5, will correspond to a volume 

 of one-fortieth. We shall now calculate the volume of this 

 external layer which we have supposed to be thus im- 

 pregnated with water, regarding it as a prism having for 

 its base the surface of the earth, with a height of 3000 meters, 

 which would give a mass of 1,530,000 cubic myriameters, con- 

 taining 38,000 cubic myriameters of water. The total volume of 

 the ocean being one-forty-eighth thousandth that of the globe, or 

 225,000 cubic myriameters, it follows that this layer of 3000 

 meters of earth would contain a volume of water equal to one- 

 sixth of the present ocean. Whatever may be the real value of 



