Pourtales.] 136 [October 7, 



directly through the means of forces brought into action by, and pro- 

 portionate to, the thickness of the glacial sheet. It is difficult to im- 

 agine any other way in which the ice could so operate except by the 

 change in the position of the isogeothermal hnes. 



It should be remai'ked, however, that the view of the agency of ice 

 In producing subsidence, does not seem to the author by any means 

 conclusive ; but only sufficiently probable to warrant its suggestion to 

 those students whose special knowledge of thermodynamics better fits 

 them for the discussion of such questions. 



Count Pourtales exhibited some specimens obtained by 

 dredging, at a depth of fi-om two hundred to five hundred 

 fathoms, between Cuba and the Florida Keys. 



The dredging was undertaken last winter for the United States 

 Coast Survey, and revealed an unexpected abundance of life at ex- 

 treme depths ; many of the forms obtained were quite new to science, 

 and among them some interesting Crinoids; other species, heretofore 

 only rarely discovered, were found in great abundance. Bones of the 

 Manatee were dredged from the greatest depths, and their occurrence 

 in such a place was a perplexing problem, since the animal is not 

 supposed to venture out to sea, and no currents are known which 

 could carry them to this locality. 



Mr. N". S. Shaler made some remarks on the disappearance 

 of the cane from the central part of the Ohio valley. 



The western and central portions of the United States afford an 

 excellent field for the observations of the naturahst ujjon the modifi- 

 cations of the fauna and flora, effected by the introduction of civilized 

 man. Among those effects, probably the most remarkable is the 

 complete extinction of the cane, Arundinaria niacrosperma Mich., 

 from an extensive area, where, half a century ago, it was one of the 

 most common and characteristic plants. The first white settlers in 

 the region now occupied by the southern parts of the States of Ohio 

 and Indiana, and the northern part of Kentucky, found a great part 

 of the alluvial lands, and much of the more fertile uplands, covered 

 with a thick growth of this plant. Generally it was that form known 

 as the " small cane," thus separated by the old hunters from the 

 larger and jiossibly specifically distinct plant, called the " tall cane." 

 Within half a century, without any purpose on the part of man to 

 destroy the plant, it has disappeared in the whole of Southern Ohio 



