Editorial Comment. 323 
not been observed in good preservation. The observed rela- 
tion of the corrosion zones with the upper Hmits of the strati- 
graphic and faunal divisions or beds lends however an ad- 
ditional significance to these in the upper parts of the series 
and wherever they occur although unaccompanied by corro- 
sion or erosion phenomena. 
EDITORIAL COMMENT. 
Dryg.^lski's Gl.acial Studie.s i\ Greenland. 
The Geographical Society of Berlin has published the re- 
port of its scientific expeditions to Greenland, which were 
under the direction of Dr. Erich von Dr\galski, in 1891, and 
again leaving Copenhagen on May i, 1892, and returning Oc- 
tober 14, 1893. The work is in two volumes (pages 556 and 
571, with 53 plates, 10 maps, and 85 illustrations in the text; 
Berlin, VV. H. Kiihl, 1897). Studies of the inland ice-sheet 
by Drygalski were the chief purpose of these expeditions, 
the district selected for special examination being that ad- 
joining the Umanak fjord. 
Much attention is given in this report to the questions of 
the probable configuration of the interior of Greenland, 
under its thick ice-sheet, and of the ph}sical conditions of 
outflow of the ice. The processes of glacial erosion, trans- 
portation, and deposition of the drift are very instructive!)- 
described and discussed; and the author's general conclu- 
sions are well summarized by Prof. James Geikie in a review 
given in Nature (vol. 58, pp. 413-416, Sept. i, 1898), as fol- 
lows: 
With regard to the ground-moraine itself, there can be no question 
that this is partly carried in the lower portions of the ice, and partlv 
pushed forward underneath, and, further, that the forward movement 
must result in the deformation of underlying unconsolidated formations. 
The moving force is, of course, in the ice itself. With the augmentation 
of included debris the mobility of the mass is impaired, internal friction 
increasing the more closely the materials are crowded together. It is 
only when debris is well saturated that under pressure movements like 
those of the ice itself can take place. In a compact subglacial mass of 
debris the mo\ement communicated by the flowing ice above nuist, 
