270 Dr. William B. Carpenter [Jan. 23, 



times that amonnt would be required to raise any large areas of the 

 ocean- bed above the existing sea-level. 



Many Geologists who would not accept in all their fulness Sir C. 

 Lyell's rather sweeping assertions, seem by their language to imply 

 their belief in less extensive interchanges between Land and Sea ; in 

 fact, I think a general belief has been entertained of a sort of see-saw 

 movement in the Earth's crust, — one portion going up while another 

 goes down, — which has seemed to draw confirmation from Mr. 

 Darwin's admirable researches on Coral Islands. 



Some of the ablest among living Geologists, on the other hand, 

 have been led by the convergence of several independent lines of 

 inquiry — of which it is my purpose to give you a concise sketch — to 

 a belief in i\iQ permanence, throughout all geological time, of what may 

 be called the framework of the existing Continents, on the one hand, 

 and of the real Oceanic basins on the other. According to this view, 

 the repeated changes which have unquestionably occurred at various 

 periods in the distribution of sea and land, have been generally pro- 

 duced by elevations and subsidences, for the most part of very mode- 

 rate amount, in portions of elevated areas in the original crust of 

 the earth, which occupied the general position of our existing Conti- 

 nents ; the upheaval of lofty mountain-chains, and the formation of 

 very deep local troughs, in which long successions of sedimentary 

 deposits have been formed, having taken place in parts of those 

 originally elevated areas, especially near their margins. The far 

 larger Oceanic basins on this view, occupy areas of the crust which 

 were originally depressed by an abrupt border, many thousands of feet 

 beneath the continental platforms ; and, like them, had a nearly 

 uniform level, until disturbed by local upheavals and depressions 

 occasioned by forces subsequently generated during the progressive 

 contraction of the molten sphere within — these upheavals and depres- 

 sions, when considerable vertically, being usually limited in area, and 

 only breaking the general uniformity of bottom-level as the elevation 

 of the Ural chain interrupts the uniformity of the great plain of 

 north-east Europe and northern Asia. 



I. Now the first consideration to which I would draw your atten- 

 tion, is the enormous disproportion which we now know to exist 

 between the depth of the real Ocean-floors beneath the sea-level, 

 and the lieiglit of the Land elevated above it ; which, when taken in 

 connection with the relative areas of the existing Sea and Land, 

 seems to render it highly improbable that interchanges extending 

 over large portions of the earth's surface could ever have taken place 

 between them. — The proportion which the area of the existing Land 

 bears to that of the Sea may be conveniently stated as about 1 to 2J, 

 or as 4 : 11 ; so that, if the entire surface of the globe were divided 

 into fifteen equal parts, the Land would occupy only four of these, or 

 rather more than a quarter, whilst the Sea would cover eleven, or 

 rather less than three-quarters. But when we compare the volume of 



