246 Mr. J. Croll on the ' Challenger's 3 Crucial Test of the 



of columns A and B which lies above the equilibrium level of 

 its base. And of course in computing the extent of the expan- 

 sion of columns A and B, I have taken into account not the 

 entire length of these columns, but only that portion which lies 

 above that level. Suppose a depth of ocean equal to that of 

 column C to extend to the North Pole and the polar water to have 

 a uniform temperature of 33° from the surface to the bottom, 

 then, in order to equilibrium, the surface of the ocean at the 

 equator would require to be 4 feet 6 inches above that at the 

 pole. But the surface of the ocean at B would be 7 feet, and 

 at A 8 feet above the pole. Gravitation never could have 

 caused the ocean to assume this form. It is impossible that 

 this immense mass of warm water, extending to such a depth 

 in the North Atlantic, can have been brought from equatorial 

 regions by means of gravitation. And even if we suppose this 

 accumulation of warm water can be accounted for by some other 

 means, still its presence precludes the possibility of any such 

 surface-flow as that advocated by Dr. Carpenter. For so long 

 as the North Atlantic stands 3J- feet above the level of the 

 equator, gravitation can never move the equatorial waters 

 polewards. 



It will not do as an objection to assert that according to the 

 gravitation theory the ocean never attains to a condition of static 

 equilibrium. This is perfectly true, as I have shown on a former 

 occasion*; but then it is the equator that is kept below and the 

 poles above the level of equilibrium ; consequently the disturb- 

 ance of equilibrium between the equatorial and polar columns 

 would actually tend to make the difference of level between the 

 equator and the Atlantic greater than 3 J feet, and not less, as 

 the objection would imply. 



There is another feature of this section irreconcilable with the 

 gravitation theory. It will be observed that the accumulation 

 of warm water is all in the North Atlantic, and that there is little 

 or none in the south. But according to the gravitation theory, 

 it ought to have been the reverse. For, owing to the unrestricted 

 communication between the equatorial and antartic regions, the 

 general flow of water towards the south pole is, according to 

 that theory, supposed to be greater than towards the north ; and 

 consequently the quantity of warm equatorial water in the South 

 Atlantic ought also to be greater ; Dr. Carpenter himself seems 

 to be aware of this difficulty besetting the theory, and meets it 

 by stating that " the upper stratum of the North Atlantic is not 

 nearly as much cooled down by its limited polar underflow as 

 that of the South Atlantic is by the vast movement of antarctic 

 water which is constantly taking place towards the equator." 

 * Phil. Mag. October 1871 ; 'Climate and Time,' Chapter ix. 



