THE PRIMITIVE OCEAN 13 



continents would be felt is difficult to say, though the 

 problem is probably not beyond the reach of mathematical 

 analysis ; if it affected an outer envelope twenty-five miles 

 in thickness, a lineal expansion of 4 per cent, would 

 suffice to explain the origin of ocean basins. If now we 

 refer to the dilatation determined by Carl Barus for rise 

 in temperature in the case of diabase, we find that 

 between 1,093 and 1,112 C. the increase in volume is 

 3'3 per cent. As a further factor in deepening the ocean 

 basins may be included the compressive effect of the 

 increase in load over the ocean floor ; this increase is 

 equal to the pressure of a column of water 0*675 mile in 

 height, and its effect in raising the fusion-point would be 

 2 C., from which we may gain some kind of idea of the 

 amount of compression it might produce on the yielding 

 interior of the crust. To admit that these views are 

 speculative will be to confess nothing ; but they certainly 

 account for a good deal. They not only give us ocean 

 basins, but basins of the kind we want, that is, to use a 

 crude comparison once made by the late Dr. Carpenter, 

 basins of a tea-tray form, having a somewhat flat floor 

 and steeply sloping sides ; they also help to explain how 

 it is that the value of gravity is greater over the ocean 

 than over the land. 



The ocean when first formed would consist of highly 

 heated water, and this, as is well known, is an energetic 

 chemical reagent when brought into contact with silicates 

 like those which formed the primitive crust. As a result 

 of its action saline solutions and chemical deposits would 

 be formed ; the latter, however, would probably be of no 

 great thickness, for the time occupied by the ocean in 

 cooling to a temperature not far removed from the present 

 would probably be included within a few hundreds of 

 years. 



The course of events now becomes somewhat obscure, 



