82 



These investigations are highly interesting to 

 the physical history of our planet. Does the 

 quantity of free caloric remain the same during 

 thousands of years ? have the mean temperatures 

 corresponding to different parallels augmented, 

 or diminished, since the last revolution that al- 

 tered the surface of the Globe? We cannot an- 

 swer these questions in the present state of our 

 knowledge ; we are ignorant of every thing that 

 relates to a general change of the climates, as we 

 know not whether the barometric pressure of 

 the atmosphere, the quantity of oxygen, the in- 

 tensity of the magnetic powers, and a great 

 number of other phenomena, have undergone 

 any change since the time of Noah, of Xisuthris, 

 or Menou. As a local variation in the temper- 

 ature of the ocean at it's surface might be the 

 effect of a progressive change in the direction of 

 the currents, which bring hotter or colder water, 

 according as they come from lower or higher 

 latitudes ; so, in a very limited extent of sea, a 

 similar refrigeration might be produced by the 

 conflict of oblique and submarine currents, which 

 mix the waters of the bottom with those at the 

 surface ; but we can draw no general conclu- 

 sions from changes that have taken place on a 



were all made at sea, except those, from which the mean tem- 

 perature for the latitude of 34° was deduced. For these we 

 are indebted to Mr. Sparmann, during his stay at the Cape of 

 Good Hope. 



