September 18, 1896.] 



SCIENCE. 



385 



the present St. Croix valley near the mouth 

 of the Sunrise Elver, and emptied into the 

 Mississippi between Anoka and Minneapo- 

 lis, while the lower St. Croix Yalley was 

 occupied only by the waters of the Apple 

 Eiver. The intermediate portion of the 

 present St. Croix River, including the pic- 

 turesque gorges called the Dalles, is attrib- 

 uted to the Aftonian and Wisconsin stages 

 of the Glacial period. In his paper on the 

 Cuyahoga Preglacial Gorge, Mr. Upham 

 presented evidence that that valley was 

 deeper than had been indicated by facts 

 previously known, new reports of wells giv- 

 ing a depth of 350 to 470 feet below the 

 surface of Lake Erie. 



Prof. J. E. Todd gave an interesting re- 

 view of the Moraines in Minnesota. These 

 moraines were mapped by Mr. Upham as 

 extending east and west in nearly straight 

 lines without regard to the topography of 

 the country. Such a position seems a priori 

 improbable ; and, according to Prof. Todd's 

 observations, the morainic accumulations 

 may be considered as forming a series of 

 concentric curves around lobes of the ice 

 sheet. 



Prof. I. C. White, in his paper on the 

 High Terrace Deposits of the Monongahela 

 Eiver, attributed them to a Monongahela 

 Lake, made by the ice sheet damming up 

 the Monongahela Piver, whose outlet in 

 preglacial time was northward into the 

 Erie basin. In the discussion of this paper, 

 Mr. Gilbert called attention to the remark- 

 able fact that the two main tributaries of 

 the Mississippi, the Ohio on the east and 

 the Missouri on the west, are both in large 

 part streams of postglacial origin. 



While the subject of Pleistocene Geology 

 occupied a large part of the attention of the 

 Section, other departments of geology were 

 by no means neglected. Dr. E. O. Hovey 

 gave an interesting account of an artesian 

 boring at Key West, Fla., reaching a depth 

 of 2000 feet. The boring was in limestone 



for the whole distance, although the rock 

 exhibited considerable variation in texture. 

 By the evidence of characteristic fossils, the 

 summit of the Vicksburg formation was rec- 

 ognized 700 feet below the surface. 



Prof. I. E. Todd presented interesting 

 data from the numerous artesian wells in 

 Dakota and the adjacent regions, whose 

 abundant water supply is derived from the 

 Dakota formation. In general, the water 

 pressure in these wells is found to diminish 

 eastward, but with local variations which 

 it is by no means easy to explain. 



Rev. H. C. Hovey, D. D., presented a 

 paper on the Making of Mammoth Cave, 

 which he attributed purely to the solvent 

 action of water upon the limestone. 

 I^either seismic disturbance, nor a sup- 

 posed pot-hole action in the deep pits or 

 depressions of the cave, can be considered 

 to have had any considerable effect. Many 

 measurements were given of different parts 

 of the cave, which Dr. Hovey and his as- 

 sociates have most thoroughly explored. 

 Dr. Hovey also described a newly discovered 

 cave called the Colossal Cave. 



Mr. AV J McGee's paper on Sheet-flood 

 Erosion called attention to the remarkable 

 conditions existing in Papagueria, a district 

 lying in southwestern Arizona and west- 

 ern Sonora, where an extensive area be- 

 tween mountain ranges has been planed off 

 by the erosive action of water, and veneered 

 with a thin sedimentary deposit. The ero- 

 sion and deposition are due, not to streams 

 concentrated in definite channels, but to the 

 flowing of waters in broad sheets over the 

 region after violent rains. 



Prof. B. K. Emerson, in his paper on the 

 Tuff Beds and other features of the Con- 

 necticut Valley Trias, called attention to 

 some very remarkable phenomena. In 

 some localities the broken surface of the 

 extrusive trap sheets, with the calcare- 

 ous or arenaceous deposits mingled with 

 the trap, has been rolled under in the 



