May 29, 1896.] 



SCIENCE. 



799 



Pleistocene 



The relations of the epochs, as conceived 

 "by the writer, are shown in the following 

 scheme : 



Period. Epoch. Process. 



Wisconsin .... Glaciation. 



Toronto ? Aqueous erosion, etc. 



lowan Glaciation. 



Aftonian Aqueous erosion, forest 



growth, etc. 

 [ Kansan Glaciation. 



f Ozarkian Canyon cutting. 



JSf eocene -j Lafayette Sedimentation. 



[ Tennessee Planation. 



Save occasionally in the Appalachian and 

 Piedmont provinces, where the normal 

 land forms are locally dominated by struc- 

 i;ural mountains, monadnocks and catoctins, 

 the topographic record of the two Neocene 

 ■erosion epochs stands out in every typical 

 landscape from the fall-line to the drift 

 margin ; for the characteristic tabular or 

 .gently-rounded, residuum-mantled divides 

 represent the earlier, and the no less char- 

 .acteristic steep-blufifed labyrinthine gorges 

 represent the later epoch. The even-topped 

 ranges and outlying monadocks record 

 •earlier episodes in continental development, 

 as Davis, Hayes, Campbell and others have 

 shown ; but the record found in the rela- 

 tively modern plateaus and gorges is many 

 times the more extensive and impressive. 



Howsoever the Ozarkian be classified, it 

 is evident that the erosion epochs of the 

 Pleistocene and Neocene were long, espe- 

 cially in the earlier time. Eecent re- 

 searches, notably by Chamberlin and others 

 in the interior and by Salisbury in New 

 Jersey, indicate that the Toronto epoch was 

 much longer than the post-glacial epoch; 

 and it has for some time been recognized 

 by a number of glacialists that the inter- 

 glacial epoch called Aftonian was much 

 longer, as measured by erosion, than all 

 those that have followed — or, at any rate, 

 that the Kansan was many times more re- 

 mote than the Wisconsin. Yet the erosion 

 of the Toronto and Aftonian together is 

 -trifling in comparison with the profound and 



widespread canyon-cutting of the Ozark- 

 ian, during which the streams and larger 

 rivers of the southeastern sub-continent 

 cjit gorges averaging 250 feet in depth and 

 ranging from a few rods to several miles in 

 width ; and even this enormous erosion is 

 slight in comparison with the widespread 

 wasting of the Tennessee epoch. 



W J McGee. 



CURRENT NOTES ON PHYSIOGRAPHY. 



GEOGRAPHICAL DESCRIPTION OF THE 



BRITISH ISLANDS. 



Dr. H. R, Mill gives in the April Geo- 

 graphical Journal an account of his plan for 

 a series of memoirs, one for each sheet of 

 the one-inch ordnance survey, describing 

 the geography of the British Islands in a 

 most comprehensive manner. Index of 

 names and locations, mean elevations, hyp- 

 sographical description, phj^siographical ex- 

 planation, areas of woodland, moorland, 

 cultivated land, etc., political and histori- 

 cal boundaries and events, geographical de- 

 scription proper, and bibliography, are to be 

 duly considered. The j)lan was favorably 

 commented on at a meeting of the Royal 

 Geographical Society, and it does not seem 

 impossible that it may be carried into exe- 

 cution. 



The remark made under ' historical infor- 

 mation ' might be applied to all parts of the 

 plan : It ' would be very stringently edited, 

 so as to confine it strictly to those features 

 and events of direct geographical impor- 

 tance,' for an inspection of current geograph- 

 ical literature shows how vague is the prev- 

 alent conception as to the essential quality 

 of geographical discipline. Local floras 

 and faunas, one of the proposed topics, are 

 distinctly not geographical, but biological 

 subjects. Treated with relation to the con- 

 trols of their distribution, they gain geo- 

 graphical flavor. Treated as exhibiting 

 geographical controls, they become as dis- 

 tinctly geographical as are any other means 



