the Contortions in Palceozoic Strata. 63 



have taken place, and below the ocean strata may still lie 

 horizontal as when first laid down. 



It will be objected further, that the strike of palaeozoic 

 strata is not always meridianal. This, I think, is no more 

 than might naturally be expected. The contortions of strata 

 could only take place over such portions of the substratum 

 as gave way under the gravitating pressure. If any of these 

 yielding areas happened to run in a zig zag direction, like 

 the course of the Andes, for example, the strike of the super- 

 incumbent rocks would be materially influenced. And, 

 again, local disturbances, such as might be caused by 

 volcanic action, may have materially tended to give certain 

 local directions to the strike. 



It must not be lost sight of, either, that if the earth is 

 really formed of a thin crust covering a still molten centre, 

 and if even this crust at one time existed in a molten state, 

 there is no possible alternative but to suppose that, as the 

 heated mass gradually lost heat, the whole would greatly 

 contract. The result of such contraction would be somewhat 

 to diminish the tendency to bulge out at the poles, to in- 

 crease the puckers at the equator, to remove the regions of 

 quiescence to higher and higher northern and southern 

 latitudes, and, perhaps, a little to increase the complication 

 of the various puckerings seen upon the earth's surface. 



This idea of the earth contracting by loss of heat is by no 

 means new, the only difficulty being an astronomical one, 

 since any diminution in the earth's volume would result in 

 an increased rate of diurnal revolution, and no such increase 

 is to be detected by the nicest observations. But may it 

 not happen that, just at the present moment, these two 

 results balance each other ? May not the acceleration con- 

 sequent upon contraction be, at this time, exactly counteracted 

 by the retardation arising from friction of the tidal wave 

 and currental influence ? 



It will, perhaps, be objected, that the time requisite to 

 bring about the observed changes in this manner would be 

 immensely beyond the limits of all reasonable hypothesis. 

 I am, however, not quite sure of that. Take the whole series 

 of rocks, and, in imagination, run over the list, from the 

 granite upwards to the last bed of tertiary deposits. In 

 Victoria alone Mr. Selwyn calculates the Silurian rocks to 

 be upwards of 35,000 feet (nearly seven miles) in thickness, 

 and this is only a fraction of the great thickness of strata 

 manifested in other parts of the world. Kemember that a 



