May 18, 1900.] 



SCIENCE. 



791 



detritus agitated by the waves. Tlie waves 

 and undertow move the shallow water near the 

 shore rapidly to and fro, and in so doing mo- 

 mentarily lift some particles, and roll others 

 forward and back. The particles thus wholly 

 or partially sustained by the water are at the 

 same moment carried in a direction parallel to 

 the shore by the shore current. The shore 

 current is nearly always gentle and has of itself 

 no power to move detritus " ( U. S. Geol. Surv., 

 Monogr. i, 37). Tarr describes ' Shore currents 

 of wind drift origin ' in Cayuga Lake, and 

 Woodman recognizes in the Bras D'Or Lakes, 

 ' currents caused by the unobstructed forward 

 movement of the top water under wave growth 

 and motion, and lasting little if any time after 

 the cessation of the wind.' It is precisely these 

 currents which Gilbert and Gulliver seem to 

 have had in mind as determining the direction 

 of 'long shore transportation of gravel and sand, 

 jostled by the waves. All may agree with a 

 later writer that "one will never find [these] 

 currents of sufficient power to transport peb- 

 bles,' if the currents are considered apart from 

 the waves ; but some might not agree with an- 

 other writer that such currents should be classed 

 'under the general head of wave action." 

 Certainly it is by wave action that a cobble is 

 thrown upon the beach ; but the systematic 

 forms assumed by cusps and bars, of which the 

 beach is but the higher part, suggests a control 

 by the slow movement of a large body of water. 

 The similarity between large cusps, such as 

 Capes Lookout and Hatteras where the action 

 of 'long-shope currents can hardly be doubted, 

 and the small forms of the Bras D'Or lakes 

 where the 'long-shore currents must be very 

 weak, suggests that. the processes of origin 

 should be similarly analyzed for both large and 

 small forms. 



GLACIAL EROSION IN THE GREAT GLEN OP 

 SCOTLAND. 



W. T. Blanford, veteran geologist of India, 

 writing "On a particular form of surface, ap- 

 parently the result of glacial ei-osion, seen on 

 Loch Lochy and elsewhere" (Quart. Journ. 

 Oeol. Soc, Ivi, 1900, 198-204), suggests that 

 glacial action has strongly deepened the floor 

 and smoothed the sides of the Great glen of 



Scotland. It is inferred that in preglacial time 

 the streams of lateral glens were separated by 

 advancing spurs which buttressed the sides of 

 the Great glen. Now the spurs seem to have 

 been truncated, producing the smooth and even 

 sides of the glen, to which attention is especially 

 directed. The lateral glens at present open 

 1000 feet above the floor of the Great glen, 

 whose smoothed sides are very little eroded by 

 the descending tributary streams. The change 

 from the inferred preglacial form is taken to in- 

 dicate glacial erosion of at least 250 or 300 feet 

 of rock. 



Main valleys thus affected by glacial erosion 

 are called ' over-deepened valleys ' by Penck, 

 because they frequently contain lakes, and be- 

 cause their slope is often so gentle that the 

 streams which now occupy them must aggrade 

 their floor. The lateral valleys that open in 

 the wall of the main valley at a considerable 

 height above its floor, so that the side streams 

 cascade into the main valleys, are called ' hang- 

 ing valleys' by Gilbert, who has described many 

 examples in an address on the Harriman 

 Alaskan expedition (not yet published). Gan- 

 nett has clearly explained the relation of hang- 

 ing side valleys to their overdeepened main 

 valleys in his account of Lake Chelan [Nat. 

 Geogr. Mag., ix., 1898, 417-428), in which the 

 analogy between the valleys and beds of rivers 

 and glaciers was clearly pointed out in terms 

 very similar to those independently stated by 

 Penck a year later (see Science, January 5, 

 1900, 34). An account of the overdeepened 

 valleys of the Ticino in the Southern Alps is 

 given by the undersigned in Appalachia, ix, 

 1900, 136-156. 



W. M. Davis. 



ANTIQUITIES OF ALABAMA. 

 ' Certain Aboriginal Remains of the Ala- 

 bama River,' is the title of a paper by Mr. 

 Clarence B. Moore, of Philadelphia. This 

 memoir occupies pages 289 to 347 of Volume 

 XI. , 1899, of the Journal of the Academy of Natural 

 Sciences of Philadelphia and is also issued as a 

 bound reprint of same date. P. C. Stockhausen, 

 the publisher, has left us nothing to wish for 

 in paper and imprint. Sixty-nine illustrations 

 of pottery, shell, stone and copper objects, a 



