Elevation and Subsidence. 5 



of existing species, but if we remove the drift or loose materials, such as 

 the clay, sand aud gravel, down to the floor of solid rock,which lies beneath, 

 we should find in many places, this rock also full of petrified sea-shells, and 

 fragments of other marine animals. But these are all of extinct species. — 

 They belong to an ocean of a date vastly more ancient, than that of the 

 glacial drift, aud afford proof of more than one submergence of the country. 



It is thus all over the world. The researches of Capt. Strachy, a scien- 

 tific British Officer, in the East Indies, show that for the greater part the 

 Himalaya Mountains, are little else than a vast pile of marine remains, and 

 80 it is with the Alps, the Andes, and most of the other ranges of great 

 hills found upon the surface of the earth. There is no such condition as 

 stability in nature. All things are in a state of unceasing change, either 

 in their form or place, and although during the few years allotted to a 

 human being for his existence, little alteration can be perceived, yet during 

 the progress of ages, those changes become upon the whole so great, that 

 they transform the exterior of the world, bringing the seas to occupy the 

 places of former continents, and the continents of one age to constitute the 

 bottom of the seas of another. 



Concerning the nature of those forces which produce elevation and sub- 

 sidence of land, we have no knowledge beyond mere conjecture. Some Ge- 

 ologists suppose that in consequence of certain chemical operations in the 

 interior of the earth, great quantities of gas are generated which cause the 

 surface to swell up and by the condensation of this vapour, or its escape through 

 volcanoes, suffers it to subside at other times. Another theory is in substance, 

 that the interior heat of the planet frequently changes its place. Thus a 

 great accession of heat in the strata of rock beneath the bottom of the At- 

 lantic, might so expand those rocks as to raise them above the surface of 

 the ocean, and in the same way the withdrawal of the heat to som.e other 

 region, might suffer the newly created continent to sink down again. It is • 

 also supposed that the cbanges in the relative distribution of land and water, 

 may be the effect of the earth's contraction. The philosophers who advocate 

 this latter theory, think tliat the ^arth was originally in a fluid state, from 

 intense heat — that it has cooled down to its present temperature, and that 

 during this refrigeration, its dimensions have become less. They urge, that 

 while contracting, its surface would be variously folded into ridges of moun- 

 tains, depressions and elevations which would not always occupy the same 

 place. Hence, a tract at one time forced upwards by lateral pressure, 

 would at another time be let down by the transfer of the force to a different 

 point. Either of those causes might produce some of the effects ascribed 

 to them : but as yet, we have no proof that a single eaf thquake, volcano, 

 elevation or subsidence has thus been occasioned. The forces to which these 

 phenomena owe their origin, appear to be exerted far beneath the surface, 

 ond will probably never be observed by maiii. 



Geology is a science of a recent date, and in order to exhibit the state of 

 opinion in Europe, within the last two hundred years, upon the subjects it 

 investigates, we shall here give a short digest of some of the principal theo- 

 ries that have been put forth during that period. These are to a certain 



