GEOLOGICAL SOCIETY OF MANCHESTER. 



187 



to the alterations in the temperature of the ocean, was not 

 only original, but one which would account for many of those 

 geological phenomena of which no satisfactory explanation 

 had hitherto been given. 



Dr. Black thought the Society was much indebted to the 

 author of the paper just read ; but he could not help remark- 

 ing, that there were many objectionable points in it. There 

 was something said in it about boulders in the torrid zone : 

 now he was not aware that boulders had ever been discovered 

 in that part of the globe. Again, it appeared from the rea- 

 soning adopted by the writer, that he assumed the law affecting 

 the specific gravity of sea water to be the same as that of 

 fresh water ; a point which was by no means well ascertained. 

 If all the waters of the ocean had been fresh, then the data 

 with which he set out, viz. that the greatest specific gravity 

 of water is at a temperature of 39^ to 40^, would have been 

 perfectly correct; but as it so happens that the greatest 

 specific gravity of sea water is at a much lower temperature 

 than that of fresh, this affected the whole of the theory. 



The Chairman understood that it was very doubtful whe- 

 ther the law by which the specific gravity of salt water is 

 determined, was the same as that relating to fresh. He was 

 inclined to think, that the greatest specific gravity of salt 

 water was at a temperature of 20^. 



Dr. Black agreed with Mr. Binney, that if the hypothesis 

 were well founded, it would go far to explain many things in 

 geology. 



Mr. Binney, in relation to what had fallen from Dr. Black 

 about the existence of boulders in the torrid zone, said he had 

 never heard of any having been found there ; but they all 

 knew that Professor Agassiz was of opinion that the entire 

 continent of Europe had formerly been one vast glacier. 

 Now, if that was the case, might they not find in it a corro- 



