116 The American Geologist. February, 1902. 
How many of the details adopted by the congress and 
recommended to students of the science in cartography, no- 
menclature, and petrographic classification, may be ultimately 
changed no one can say, but whatever or however important 
they may be, it will be easier to have them generally adopted 
when they are made as amendments or additions to a recog- 
nized code, just as it is easier to pass an intelligible law on the 
basis of a bill which brings the requirements in concrete form 
before the law makers. 
The present lexicon was edited from the preliminary proofs 
of a work on this subject prepared by M. Léwinson-Lessing 
and submitted to the committee on nomenclature and to the 
petrographers of the VIIIth Congress. One hundred copies 
of these proof sheets in French were printed and distributed 
to the above named recipients before the meeting of the last 
Congress. Of these thirty proofs with proposed changes were 
returned to M. Barrois, and M. Lowinson-Lessing added some 
new material. M. Barrois has shown excellent judgment in 
exercising the responsible task assigned him of deciding be- 
tween conflicting definitions of the same word, and in neces- 
sary suppressions as well as in the choice of what he has 
given. The lexicon will unquestionably be further amended 
and enriched, but even as it stands it is the most positive and 
direct contribution which has ever been made to science by 
so authoritative a body as the Congress of which M. Barrois 
so ably filled the duties of general secretary, and it is a fitting 
climax to the admirable volume of that Congress’s proceed- 
ings. 
EDITORIAL COMMENT. 
THE QUESTION OF THE UNIT OF GEOLOGICAL MAPPING. 
The growing conviction among the geologists of the United 
States Geological Survey that the requirements laid down in 
the Tenth Annual Report of the Director (J. W. Powell) for 
the construction of maps on the basis of the physical unit 
alone, can effect but a partial and imperfect expression of geo- 
logical events, led to the important conferences last winter be- 
