274 Dr. William B. Carpenier [Jan. 23, 



deepest of tte smaller depressions anywhere occurring in Land- 

 areas. 



The occurrence of these gigantic pit-holes in this region of 

 extraordinary Volcanic activity has a singular significance ; especially 

 when taken in connection with the fact that like depressions of the 

 Ocean-bed which have been elsewhere met witb, are also in Volcanic 

 areas. Thus the first of the ' Challenger ' soundings which showed a 

 depth (3876 fathoms) greatly exceeding that of the ordinary floor of 

 the Atlantic, was made not far north of St. Thomas's, in what may be 

 regarded as a continuation of that " line of fire " which is so marked 

 in the lesser Antilles. The sounding-wire of the United States ship 

 ' Tuscarora ' twice broke, without reaching bottom, in near proximity 

 to the volcanic region of Japan, at depths considerably exceeding 

 4000 fathoms. And the deepest bottom sounded by the ' Challenger,' 

 4575 fathoms or 27,450 feet, — which seems to have been a local depres- 

 sion of a sea-bed averaging about half that depth, and was met with 

 on the passage between New Guinea and Japan, not far from the 

 Ladrone Islands, — was also presumably in a line of volcanic dis- 

 turbance. 



Again, the 'Challenger' observations enable it to be affirmed 

 with confidence, that wherever Land shows itself * in the great Oceanic 

 area, forming what are distinguished as " oceanic islands " from those 

 which are merely outlying portions of continental platforms, those 

 islands are all volcanic ; their elevation having been due to forces acting 

 only in limited spots or over particular lines, and not to any general 

 uplifting of the bottom of the basin. So, on the other hand, the 

 contours of the Deep-sea bed, so far as they have been determined, 

 give no countenance whatever to the notion of such a general 

 subsidence as would have produced the submergence of a great 

 Continental platform in any part of the vast Oceanic area ; and this 

 negative conclusion receives striking confirmation (as will hereafter 

 appear) from the entire absence, in the sediments at present in process 

 of deposition at a distance from existing continental land, of any 

 traces of land-degradation. 



II. The progress of Geological inquiry has now made it apparent 

 that the movements of elevation that have occurred from time to time 

 in various parts of the Land-areas of the globe, have been the result 

 of forces acting in two difierent directions — vertical and horizontal. 

 Extensive platforms, of which European Russia affords a conspicuous 

 example, have been several times raised into land (with alternations 

 of depression) by a force that seems to have operated directly upward ; 

 and with such uniformity over a vast area, as to have produced very 



* As in all the Coral islands in which basal rock shows itself, that rock is 

 Volcanic, the same may fairly be presumed to be the character of tlie submerged 

 peaks on which those " atolls " rest, above whose level platforms no rocky base 

 now rises. 



