﻿GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 293 



feet, is greater than that, about 120 feet, indicated for the areas 

 already considered, urdess the notches in the outer edges of the St. 

 Martin Plateau and the Virgin Bank really indicate a position of sea 

 level 40 fathoms lower than present sea level. 



BERMUDAS. 



Alexander Agassiz has given a good account of proto-Bermuda, that 

 is of the extent and general physical character of the Bermudas pre- 

 vious to the submergence that has left the group in very nearly the 

 form in which we now know it.^ Recently Prof, L. V. Pir-:son has con- 

 tributed two highly valuable articles to the literature on the geology 

 of the islands, basing his interpretations largely upon a study of 

 samples from a weU bored in Southampton Parish, on the slope of a 

 hill about a mile west of the lighthouse on Gibbs Hill, from a height 

 of 135 feet above sea level to a depth of 1,413 feet below the surface, 

 or to a depth of 1,278 feet below sea level.- 



There were penetrated in the well mentioned three major classes 

 of material, as follows: (1) From the surface to a depth 383 feet 

 below it, limestone; (2) from 383 feet to 600 feet, oxidized volcanic 

 material; (3) below 600 feet to 1,413 feet, with one shght exception, 

 basaltic, usually black lava. Pirsson concludes the first of his two 

 articles with the following statement: 



It appears to the writer that what has b.een learned regarding the history of the 

 Bermuda volcano has an important bearing on the question of the way in which the 

 platforms on which coral islands, barrier reefs and atolls are situated, have been 

 formed. There is of course nothing new in the idea that these may be volcanic in 

 origin, only in Bermuda we have once more a positive demonstration of the fact. We 

 have also seen that, provided the volcanic masses are of sufficient antiquity, they 

 may, even though of great size, have been reduced to sea level, furnishing platforms 

 of wide extent. As mentioned above, such masses reduced to sea level would con- 

 tinue to project from the ocean abysses indefinitely and many of them may be of great 

 geologic age. There is nothing in the mere size of any of the atolls of the Pacific which 

 would preclude their being placed on the stumps of former volcanic masses; it is not 

 intended to assert by this that the foundation in every case is necessarily a volcanic 

 one. If such masses have once been brought down to sea level and continue to exist 

 and that level changes within limits from time to time by warpings in different places 

 of the sea floor, or by an accumulation of ice on the lands and its melting, as suggested 

 by Daly, then conditions of shallow water over them may be established suitable for 

 their colonization by those organisms concerned in the production of the so-called 

 coral reefs, which may be formed under the conditions postulated by Vaughan. 



It was the understanding between Professor Pirsson and me that 

 I should prepare a report on the calcium -carbonate samples. The 

 followmg is a prehminary statement, accompanied by determinations 

 of the Foraminifera by Dr. Joseph A. Cushman. 



1 Agassiz, Alexander, A visit to the Bermudas in March, 1894, Mus. Gomp. Zool. Bull., vol. 26, pp. 273- 

 277, pi. 2, 1895. 



2 Pirsson, L. V., Geology of Bermuda Island, I. The igneous platform, Amer. Joum. Sci., ser. 4, vol. 38, 

 pp. 189-206; II. Petrologyofthelavas, Idem., pp. 331-344, 1914. 



