DECEMBER 10, 1897.] 
External processes are grouped under 
ground water, weathering, sliding, rivers, 
glaciers, winds, waves and sedimentation. 
Forms are classified under those of the sea 
and of the lands; the latter being plains, 
escarpments, mountains, valleys, dissected 
regions (thallandschaften), basins, caverns, 
and the large forms of the land surface 
(mountains, plateaus, depressions). The 
terse style of the book shows that its au- 
thor expects those who use it to be com- 
petent teachers and faithful students. Its 
readers may be confident of trustworthy 
statements and explanations; but in the 
third part, with which these notes are par- 
ticularly concerned, there is less consid- 
eration of the genetic correlation of parts 
than would be welcomed by many. 
THE AGE OF VALLEYS. 
THE age of a valley is a measure of its 
stage of development. It may be steep 
sided and young; it may half open or 
mature; it may be wide open orold. At 
any stage in its development it may be 
submerged and buried, and thus preserved 
until some future time when it is again re- 
vealed by weathering, like any other fossil. 
In this sense the valley, whether young or 
old, may be dated as geologically ancient or 
modern. Thus there were mature valleys 
in ancient times among the St. Francis 
mountains of erystalline rocks in south- 
eastern Missouri. They are still hardly 
more than mature, for through nearly all 
Paleozoic, Mesozoic and Cenozoic time they 
have been buried ; they have only in com- 
paratively recent time come to light again, 
as their relatively weak sedimentary cover 
has weathered off. But in another sense 
these mature valleys are modern, for they 
have been re-excavated in late post-Tertiary 
time. When the ancient and modern val- 
leys coincide there may be confusion if 
they are briefly described as ‘of very an- 
cient origin,’ and this confusion appears to 
SCIENCE. 
873 
enter in the paragraph given to the deep 
eanyons of Labrador, in Adams’ review of 
Low’s report in a recent number of ScrencE 
(Nov. 13, 741). The implication here, as 
in the original report, is that the valleys 
have been valleys ever since the time of 
their ancient origin. The probability is 
very great that during most of the inter- 
vening time they have been buried, and 
that however ancient was their initial ex- 
cavation their present re-excavation is rela- 
tively modern. 
W. M. Davis. 
HARVARD UNIVERSITY. 
CURRENT NOTES ON ANTHROPOLOGY. 
THE QUESTION OF VARIATION. 
Two recent essays on variation as applied 
to man may be mentioned together, al- 
though they treat the subject from different 
points of view. The one is by Professor 
Virchow, in the Proceedings of the Berlin 
Academy of Sciences for 1896. He de- 
scribes the difference between diathesis, 
Anlage and variation, the former being the 
permanent, the latter the changing factor 
of the organism. He points out the impor- 
tant fact that progressive variation may 
arise from pathological inceptions. While 
his article has the greater bearing on ques- 
tions of medical science, it has valuable 
application in anthropology. 
The second article is by Professor Mahou- 
deau in the Revue of the Paris School of 
Anthropology for July of this year. It is 
taken up principally with pointing out the 
exact meaning of variation or transforma- 
tion in organic life as laid down by La- 
marck. The quotations show that he dis- 
tinctly taught the descent of man from . 
lower forms of life. In these respects he 
is claimed to have anticipated the most 
modern doctrines in his celebrated work, 
first published three quarters of a century 
ago. 
