60 PliOF, EDWARD HULL, LL.D., F.R.S., P.G.S., ON 



circulate over the surface of tlie ocean — but a vertical circula,tion. 

 As the waters of the Arctic and Antarctic regions pass down — at a 

 very slow rate it is true, but still they do pass down — along the bed 

 of the ocean towards the equator ; those on either hand gradually 

 rise and replace the warm water which is constantly given off by 

 the surface currents in the equatorial regions. As to the theory 

 which the Chairman has mentioned that sodium may have been in 

 a gaseous condition in the original highly heated circumincum- 

 bent air surrounding the incandescent globe — sodium gives a very 

 marked line indeed in the spectroscopic analysis of the sun and 

 of many of the heavenly bodies. But my paper refers to a more 

 advanced stage in its course of consolidation, and I start from the 

 period in which sodium, and calcium would have entered into 

 combination in the formation of rocks during the cooling of the 

 crust owing to the radiation of the original heat into space. 

 Crystalline rocks of the granitic or volcanic tyj)e may have been 

 thus formed, and then the sodium would of course be in a com- 

 bined state. It is the reaction of the supposed highly saline 

 waters, which would still have remained as an envelope outside the 

 incandescent globe, which, according to the view I have advanced, 

 would result in the formation of various salts — sodium chloride 

 being the principal and the most abundant. 



I will now refer to the communications that have been received. 



Let me say how much, gratified I feel by Professor Tyndall's 

 approval of my views. Ai regards Professor Prestwich's com- 

 munication, which gives what may be considered the alternative 

 theory regarding the origin of oceanic salinity, there is much to 

 be said. But I have for a long time regarded it as an insufii- 

 ciont hypothesis; and as regards the statement that gypsum 

 (sulphate of lime) "was deposited first," this is not generally the 

 case ; at least not in Worcestershire where the gypsum lies above 

 the rock salt, nor can I admit that the Triassic strata are of marine 

 origin in England. 



Mr. Postlethwaite's letter is of very great interest to me, 

 because it is the first case in which I have 'leard in the British 

 Isles of such highly saline water as he describes being found in 

 strata of the lower Silurian age. • I do not know of any case 

 in England, Ireland, Wales, or Scotland where these old rocks 

 have yielded such highly saline waters as he describes. They seem 

 to represent those which have been worked for so long a period 



