0O8 M. Ami Boue on the Pafaohydrogrdphy 



contraction of the earth, and by other facts given by geography 

 and geology. If we had already only an approximative esti- 

 mation of the value of each period of elevation, we could 

 answer the question about the elevations and subsidences for 

 each period in every country of the globe. 



It is not now sufficient to trace the presence of the sea 

 everywhere ; but we must determine also its depth. If we 

 knew how much, and in what quantity, a land or chain has 

 been elevated or depressed, we could determine the depth of 

 the sea-water by the height of the marine beds, which are still 

 horizontal. But we should be very prudent in such determina- 

 tions, and especially not to draw conclusions from individual 

 countries. When the obtained halves are found applicable to 

 the chief known parts of the earth, we can come to rational con- 

 clusions, for we can learn by comparison how much nearly 

 a given country is elevated or subsided. And we can hope to 

 arrive at the maxima and minima of elevations and sub- 

 sidences in a given period of time, because many formations 

 in the earth give at least a maximum of height and subsi- 

 dence. 



As I conceive the solution of the problem, it would be 

 found if the two following facts are admitted as sufficiently 

 proved: — 



1st, What the globe always was ; and if it has remained 

 the same, nothing can be lost except the heat, w T hich is of no 

 value to us in this consideration. Yet many things have been 

 changed on earth, for instance a part of the water has been 

 turned into ice, and a greater quantity of fresh -water cur- 

 rents, and of subterranean water, have taken the place of the 

 former much greater humidity in the atmosphere. Perhaps 

 the salt formations may be in some relation with this differ- 

 ence between the quantity of fresh and salt water in the 

 primitive times, and in later periods. 



2d, The protuberances and low places of the earth's sur- 

 face are in equal relations to the rigid and fluid parts of the 

 globe ; or, in other words, all the values of the heights of the 

 earth are found to differ when related with cavities. The 

 protuberances lessen the place of the fluid in the same mea- 

 sure as the corresponding cavities do make. 



