106 



SCIENGE. 



[N. S. Vol. IX. No. 212. 



An Unrecognized Process in Glacial Erosion. 



WiLLARD D. Johnson, Washiugton, D. 



C. 



The glacial topography of mouBtains was 

 analyzed, and the more distinctive forms 

 discriminated from those of aqueous erosion. 

 The recognized process, that of scour, its 

 action downward and forward with the 

 glacial advance, was described. Glacial 

 scour and aqueous erosion were regarded 

 as alike incompetent to bring about the re- 

 sults and as a rule inimical to the produc- 

 tion of known forms. An unrecognized 

 process was set forth, that of sapping, whose 

 action is horizontal and backward. The 

 tendency of glacial scour is to produce 

 sweeping curves and eventually a graded 

 slope. The tendency of the sapping process 

 is to produce benches and cliffs. Sapping 

 is altogether dominant over scour. Under 

 varying conditions, however, its developing 

 forms become obsolescent ; their modifica- 

 tion, then, by rounding off of angles, puts 

 them seemingly into the category of scour 

 forms. An hypothesis was advanced as to 

 the cause of glacial sapping. The ultimate 

 effect is truncation at the lower level of 

 glacial generation. A second analysis and 

 a more appreciative classification of transi- 

 tion types terminated the paper. 



Before discussion the next paper was read 

 because it dealt with allied phenomena. 

 The hour, however, being late, the discus- 

 sion went over till the next day. 



Geology of the Yosemite National Park. H. 



W. TuENEB, Washington, D. C. 



By means of lantern slides the author 

 illustrated the topography of the granite 

 areas in the higli Sierras and the Yosemite 

 and other allied gorges. He developed the 

 view that joints had chiefly caused the 

 precipitous cliffs, and concentric shelling 

 off, the domes. Minor forms were also ex- 

 plained. He opposed the view that fault- 

 ing had caused the gorges. 



Gold Mining in the Klondike District. J. B. 



Tyrrell, Ottawa, Ont. 



By means of a fine series of lantern 

 slides the author illustrated the geograph- 

 ical situation and the geology of the Klon- 

 dike gold-bearing gravels. The stream 

 gravels are the usual type of placers, but 

 the bench gravels are small lateral mo- 

 raines left by glaciers. The gold has not 

 been derived from any distance. 



TJie Nashua Valley Glacial Lake. W. 0, 



Crosby, Boston, Mass. 



By means of lantern slides from photo- 

 graphs and from maps and profiles based 

 on bore-holes made by the ofiBcials of 

 the Boston department of municipal water 

 supply, the speaker described the bed-rock 

 surface, the overlying gravels on the 

 Nashua Eiver, and the characters of the old 

 glacial lake of whose former existence they 

 gave evidence. 



On the conclusion of the paper, at 5:45 

 p. m., the Society adjourned until the fol- 

 lowing day. In the evening about one 

 hundred Fellows, many with their wives, 

 gathered at the Hotel Logerot for the an- 

 nual dinner. Under the presiding oversight 

 of Professor B. K. Emerson, the past grand 

 master of all the toastmasters, another en- 

 joyable gathering was added to the list of 

 those previously held. 



J. F. Kemp. 



Columbia Univeesity. 



( To he Concluded. ) 



SCIENTIFIC BOOKS. 

 Theory of Ch-oups of Finite Order. By W. Burn- 

 side, M.A., F.R.S., Professor of Mathematics 

 at the Royal Naval College, Greenwich. 

 Cambridge, The University Press. 1897. 8vo. 

 Pp. xvi + 38S. Price, S3. 75. 

 If, assuming a single but elevated point of 

 view, we describe mathematics as the science of 

 formal law, then the theory of operations easily 

 commands the field, for it is the quintessence 

 of mathematical form, the comparative anatomy. 



