January 30, J 885. 



SCIENCE. 



89 



structural changes induced b\~ mechanical 

 movements in ancient crystalline rocks have 

 nothing in common with that mysterious 

 process which has been supposed by the meta- 

 morphic school to generate similar crystalline 

 rocks from non-crystalline sediments. As re- 

 gards the changes wrought by the same agency 

 in detrital masses, it ma} r be repeated that 

 4 ' the resemblances between primitive crj'stal- 

 line rocks and what we know to be detrital 

 rocks, compressed, recemented, and often 

 exhibiting interstitial minerals of secondary 

 origin, are too slight and superficial to deceive 

 the critical student, and disappear under mi- 

 croscopical investigation." 



The doctrine of a regional and progressive 

 metamorphism as the origin of the crystalline 

 rocks, which was very widely received a gener- 

 ation since, both in Europe and America, has 

 within the last fourteen years become greatly 

 discredited. In the Alps, where it was first 

 seriously applied, as well as in Great Britain, 

 it is now generally abandoned. Callawa}' 

 wrote not long since, that "every case of 

 supposed metamorphic Cambrian and Silurian 

 has been invalidated h\ recent researches;" 

 and Bonney, now president of the Geological 

 society of London, declared, in 1883, that the 

 hitherto accredited *' instances of metamor- 

 phism in Wales, and especially in Anglesea, 

 in Cornwall, in Leicestershire, and in Worces- 

 tershire, have utterly broken down on careful 

 stud}'," as had already been the case in the 

 Alps, and, it maybe added, in North America. 

 The official geologists in Great Britain, repre- 

 senting the traditions of the old school, have, 

 however, hitherto held to the Scottish High- 

 lands as their last stronghold, which they are 

 now forced to abandon, — a substantial victory 

 for rational geology. 



T. Sterry Hunt. 



Montreal, Jan. 10. 



THE BASIN OF THE CARIBBEAN. 



The U. S. hydrographic office having sent 

 to the New-Orleans exposition, as part of its 

 exhibit, a model of the Caribbean Sea, it will 

 be interesting at this time to discuss the deep- 

 sea soundings taken by officers of the navy in 

 the coast-survey steamer Blake, and in the fish- 

 commission steamer Albatross, from 1878 to 

 1884, by means of which this model was con- 

 structed. 



Particular attention was called to this great 

 basin in the coast-survey reports for 1880 and 

 1881, and also in a paper read by the writer 



before the American Geographical Society in 

 the winter of 1882. 



It was not possible, however, to give the 

 contour of the bed of this sea until the com- 

 pletion of the work of the Albatross last win- 

 ter. The data then obtained permitted the 

 construction of the accompanying chart, which 

 is a faithful representation of the model before 

 mentioned, and by means of which it will be 

 eas} r to draw attention to some of its most im- 

 portant features. 



During the cruise of the Challenger, it was 

 demonstrated that in a submarine lake the tem- 

 perature is constant to the greatest depth, and 

 the same as that of the ocean at the depth of 

 the rim of the lake at its lowest or deepest 

 point. 



The investigations of the temperature of the 

 Gulf of Mexico by Commander Sigsbee, from 

 1874 to 1878, had shown that below a depth 

 of 800 fathoms the temperature is constant 

 at 39|-°, which is the normal temperature of 

 the ocean at that depth in the region of the 

 Equatorial Current. It was evident, therefore, 

 that the Caribbean Sea, from which the Gulf 

 of Mexico receives its waters, must be enclosed 

 by a rim which at its deepest part was 800 

 fathoms below the surface. 



The purpose of the investigations of the 

 Blake, during the time that I had the honor to 

 command, was to verify the deduction thus 

 made, and to determine the position and height 

 of this rim, which limits the low temperature 

 of the waters of the Gulf of Mexico. 



All the passages between the islands from 

 Trinidad to Cuba were carefulty sounded, and 

 the existence and position of the rim definitely 

 established. At the same time temperatures 

 were taken both outside and inside the basin, 

 and at the points of minimum depth. With 

 one exception, however, the only place where 

 the rim was sufficiently low to admit water of 

 the required temperature (39|°) was in the 

 windward passage. In all other places the 

 depths on the rim were much less than 800 

 fathoms. 



The exception noted was a narrow gully of 

 1,100 fathoms, with a bottom temperature of 

 38°, leading into a basin of 2,400 fathoms be- 

 tween Santa Cruz and St. Thomas ; this great 

 depth also having a bottom temperature of 38°. 

 As the temperature at 1,500 fathoms just south 

 of Mona Passage was 39^°, there could be no 

 doubt of the existence of a rim from Santa. 

 Crnz to Puerto Rico. The Albatross, there- 

 fore, was directed to examine this localit} 7 , and, 

 as was expected, found the ridge with 900 

 fathoms on it at the greatest depth, and a least 



