PEIMORDIAL OCEAX OP OUR GLOBE. — 117 



to take place ; and as the temperature of the solid globe and its at- 

 mosphere, chiefly of aqueous vapour, was reduced, successive portions 

 of this vapour were condensed into water and deposited in the liquid 

 form, and at a temperature which, in the then state of things, was 

 its boiling-point. The boiling-point of water upon our globe was 

 therefore a maximum when all water was held as vapour in suspen- 

 sion; and as secular cooling proceeded the boiling-point became 

 lower and lower, as the water was divided between the vapour atmo- 

 sphere stiU. in suspension and the liquid water already condensed and 

 deposited from it ; and this continued, the boiling-point constantly 

 receding, and the temperature of the liquid water at its point of 

 deposition continually lowering, until the existing state of things 

 was reached. 



So much seems to be to such an extent supported by known phy- 

 sical data that it may be considered certain. To its full esta- 

 blishment in a numerical form we need a more accurate determina- 

 tion of the total volume of water appertaining to our globe, and a 

 sufficient extension of the experimental determination of the rela- 

 tions between temperature and pressure of steam. The few deduc- 

 tions which I have made, rather by way of illustration than as at all 

 systematic, far less as exhaustive of the almost boundless field of 

 inquiry which seems to be opened up by the main propositions of this 

 paper, must be judged of for what they are worth by those who have 

 made themselves acquainted with what I have here ventured to set 

 before them. 



DiscirssiON. 



The President said he had read the paper with much interest, 

 but thought that Mr. MaUet had overestimated the possible tem- 

 perature of the first deposited water, though, indeed, we were still 

 ignorant of the critical point for water; still he doubted whether 

 water could exist at a temperature higher than a dull red heat. 

 He thought that the geological action also was overestimated; 

 nevertheless the subject had an important bearing on the structure 

 of some of the most ancient rocks. 



Mr. Evans said there was one point which separated this question 

 from the ordinary experiments made on water ; in them water was 

 held in a closed vessel ; here the heat of the vapour could radiate 

 into free space at a low temperature. Then convection might have 

 caused considerable equalization of temperatui'e before any con- 

 densation. 



Prof. Prestwich said that the cause introduced by Mr. MaUet 

 would tend rapidly to lower the temperature : if the equator and 

 poles were at different temperatures there would be such rapid air- 

 currents as to equalize the general temperature ; also if the tem- 

 perature were so high in earlier times there would be more meta- 

 morphism. 



Dr. Hicks said that aU we know of the earliest rocks was that 

 they were crystalline, but that the rocks following them had their 



