Juny 16, 1897.] 
but a piece of thin metal with a square cut 
out, as Shown in Fig. 10, may be substituted. 
In either case the square must be of such a 
size that it covers one sq. mm. on the stage 
with a given combination of objective and 
ocular, and a certain tube length to be 
found by comparison with a stage microm- 
eter. It is an advantage to have at hand 
higher powers for a more thorough study 
of the organisms met with, but for ordinary 
work the powers suggested are sufficient. 
All this apparatus, together with bottles 
for collection and note book for records 
may be carried in a grip sack, and this will 
be found generally the most convenient 
way. It is possible, however, to make a 
neat box, with compartments for holding 
the microscope, funnels, tube vials, etc., 
and I respectfully submit this to manufac- 
turers of microscopical supplies. 
GxorGEe C. WHIPPLE. 
NEWTON CENTRE, Mass. 
SPECTRUM COLOR STANDARDS. 
THE extensive adoption of the color 
standards proposed by me and put into 
practical form for educational purposes by 
Mr. Milton Bradley, of Springfield, Mass., 
leads me to offer the readers of ScrENcE an 
opportunity to examine a chart of the solar 
spectrum after Rowland with the standard 
SCIENCE. 
89 
color nomenclature within some accurate 
and practical system. The idea of teaching 
color by a system thus definitely defined 
has also proved to be very practical, not 
only in elementary instruction, but in the 
more exacting art work. This rapidly in- 
creasing public interest in the subject makes 
it seem likely that the accompaning chart 
will be of interest. 
A few observations on the practical ap- 
plication of these standards will illustrate 
the value of the scheme. The area repre- 
senting each particular standard in the 
chart is narrow enough to allow of no per- 
ceptible difference in the hue of the two 
sides of the area when viewed through the 
spectroscope and is still wide enough to 
give a clear working field. Moreover, the 
areas selected coincide with the views of a 
large number of persons experienced in the 
discrimination of color and well prepared, 
therefore, to judge what would be of practi- 
cal value as color standards and applicable 
to the various needs of the arts as well as 
to science and to educational purposes. 
And still again, though there was no direct 
reference to the theories of color vision, 
these standards having been first proposed 
nearly fifteen years since, the standards 
prove to have been happily selected as re- 
gards the more recent theories of color 
colors located upon it. The importance of 
making the spectrum the basis of all our 
work in color is recognized by all, and I 
have received many appreciative communi- 
cations from eminent men in scientific and 
educational circles, both in this country and 
England, expressing approbation of the 
effort to bring our now greatly confused 
vision. Another very important considera- 
tion is the fact that the quality of any color 
which I have yet seen can be obtained by 
the union of two of these standards. Of 
course, the intensity of one of the two com- 
pared colors will generally have to be modi- 
fied to obtain a perfect match, but I have 
never yet been unable to do this. In a 
