716 



SCIENCE. 



[N. S. Vol. III. No. 71. 



Bay, at the west of Lake Michigan, from wliich 

 it is almost entirely shut off except a very nar- 

 row strait called the ' door.' 



At these two localities the effects are quite 

 different. Mr. D. J. Woolman, of Duluth, 

 states that at the head of Lake Superior the ice, 

 which has formed in early winter some distance 

 out from the shore, usually soon becomes 

 broken up by easterly or westerly winds and is 

 subsequently piled up by the wind in a ridge 

 several feet high along the shore. In later 

 winter the ice freezes more deeply and so be- 

 comes frozen to the bottom for some distance 

 out from the shore. Beyond this limit of 

 freezing the outer ice again becomes broken up 

 by the wind, and in a similar way another 

 ridge of ice is formed a few rods from the shore, 

 roughly parallel with the first ridge, and enclos- 

 ing a sheet of smooth ice. In this way two or 

 more ridges of ice are formed parallel with the 

 shore. 



In Green Bay, however, the effect is quite 

 different. The Bay is almost entirely shut off 

 from Lake Michigan and in winter becomes en- 

 tirely frozen ovei", and after once freezing over 

 the ice is rarely broken up to any extent by 

 the wind. On the other hand, a strong wind 

 fi'om the west or northwest sometimes has 

 the effect of causing the ice to move shore- 

 ward in the direction of the wind, as a solid 

 sheet, thus piling it up along the shore to a 

 depth of sometimes sixty feet or more. A 

 movement of this kind generally occurs at least 

 once during a winter, and is fully accomplished 

 in from one to three minutes. 



In this way considerable geological work is 

 done along the shore, and it is not uncommon 

 to see, after the ice melts in spring, a pile of 

 shore debris piled up in places to a height of 

 eight feet, and showing features characteristic 

 of moraines. The amount of geological work 

 done at different points along the shore differs 

 and at any point seems rather to depend on 

 the slope of the shore and conditions other 

 than the ice movement at that point, e. g., 

 at the point where the maximum amount of ice 

 movement occurred the minimum amount of 

 work was done. Here the conditions were 

 these, viz : A steep slope just at the shore line, 

 which must have had the effect of causing the 



ice to break almost as soon as it began to move. 

 Along the shore about eight feet from the 

 original ice front, stood a pile of slabs, piled 

 loosely to a height of ten feet, and parallel 

 with the shore so as to directly oppose the ad- 

 vance of the ice. These slabs, however, though 

 completely buried for many feet by the ice 

 which pushed up over and beyond them, were 

 nevertheless scarcely disturbed. As the ice be- 

 came broken at the shore line the pieces filled 

 in between the shore and the slabs so that the 

 ice following pushed up over the ice already 

 deposited there, leaving the slabs practically 

 intact. 



T. A. Jaggab, Jr., 

 Becording Secretary. 



PROCEEDINGS OF THE TORREY BOTANICAL CLUB. 



The Club met on Tuesday evening, April 9, 

 1896, President Addison Brown in the chair, 

 and 30 persons present. Two new members 

 were elected. 



Dr. Albert Schneider read a paper on ' The 

 Uses of Lichens,' giving an instructive account 

 of the past and present uses of these plants in 

 medicine and the arts. Mr. P. A. Eydberg 

 read his announced paper entitled ' Preliminary 

 Notes on a Revision of the North American 

 species of Potentilla and Related Genera.' This 

 was accompanied by many herbarium speci- 

 mens and drawings, and drew forth remarks 

 from the President and Mrs. Britton. 



The last paper was that of Mrs. E. G. Brit- 

 ton, on 'Notes on Mexican Mosses.' Mrs. Britton 

 gave a short historical account of the various 

 collections of mosses which have been made in 

 Mexico, stating that she had recently received, 

 for naming, the specimens gathered by Pringle, 

 as well as those collected in 1S92 by Smith and 

 Brunner. Specimens from these two collec- 

 tions, as well as others from those of F. Miiller, 

 C. Mohr, Hahn, etc., were exhibited, and a 

 comparison was made of the number of genera 

 and species which are common to Mexico and 

 the United States. 



The President reminded the members of the 

 first Field Day of the season, April 25th, at 

 Prince's Bay, S. I W. A. Bastedo, 



Secretary pro tein. 



