ie PREPARNELONCOE A GEOLOGIC MWAr. 
TuHE following paper is a discussion of certain factors influ- 
encing the quality of a geologic map; and an attempt has 
been made to formulate the conditions which must be fulfilled 
before a map can be considered satisfactory. Two important 
branches of the subject, however, are not treated: the drafting 
and the process work. The quality of both is closely dependent 
on the amount of money available for the preparation of any 
particular map, and therefore neither can be discussed in a gen- 
eral way. Disregarding these more purely mechanical factors, 
the value of a geologic map depends upon the accuracy and the 
precision of the field work; on the completeness with which 
certain data, both geologic and geographic, are presented on 
the maps; and on the care with which scale, colors, conven- 
tions, etc., are chosen so as to give the best results. 
A section might, perhaps, have been devoted to a considera- 
tion of the ethical questions involved in the preparation and 
publication of a geologic map. The writer has, indeed, dis- 
cussed certain of these points, but from the point of view of 
expediency rather than of abstract justice. The ethical code 
for the cartographer is simple; he should give due credit for 
work done by others; and he should frankly acknowledge doubt 
or ignorance. The first canon requires that both the geologic 
and geographic data should be properly credited; the second, 
that geologically unknown areas should be left blank, that 
doubtful boundaries should be distinguished from those accu- 
rately traced; and that, if possible, the location of actual out- 
crops should be indicated. 
I. ACCURACY AND PRECISION OF FIELD WORK. 
The map should show geologic boundaries as precisely as the 
geographic and topographic accuracy of the base will permit. 
When, as frequently occurs, a geologic map falls below this 
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