140 
When cultured in a standard alkaline man- 
nite solution 41 per cent. of the soils failed to 
show any Azotobacter growth. The average 
nitrogen fixed, per 100 ¢.c. cultural solution, in 
such cultures was 7.76 mg. The average ni- 
trogen fixed in cultures showing Azotobacter 
was 16.22 mg. per 100 cc. cultural solution. 
A study of the reaction of these soils gave 
very interesting results. The hydrogen ion 
concentration of an aqueous extract of the 
soils was measured by the colorimetric method 
outlined by Clark and Lubs.1 
The range of hydrogen ion concentration in 
the soil extracts, prepared by shaking one part 
of soil with one part of water and centrifuging 
expressed in P,, was from 5.3 to 7.8. All of 
the extracts from soils which developed Azo- 
tobacter, with the exception of three, gave a 
P,, of 6.0 or above. . All of those which failed 
to give Azotobacter, with the exception of 
three, gave a P,, of 5.9 or less. These results 
would indicate that the absolute reaction is 
probably the major factor controlling the 
presence of Azotobacter in soils. 
P. L. Gamnry 
RESEARCH LABORATORY IN Soil BACTERIOLOGY, 
KANSAS AGRICULTURAL Exprr. STA. 
DESIGNATION OF SPECIALIZING PHYSICISTS 
PuHysicists specializing along certain defi- 
nite lines in such a way or to such a degree 
that the broad term physicist is not sufi- 
ciently descriptive of their professional activi- 
ties, are frequently at a loss for a suitable 
designation. For example, a physicist en- 
gaged in industrial physics along the lines 
of electricity may not consider himself an 
electrical engineer, and still less an “elec- 
trician ” in the ordinarily accepted use of the 
term. What shall he call himself? A phys- 
icist specializing in mechanics may be neither 
a mechanical engineer nor a mechanic or 
mechanician. Similarly one specializing in 
heat may not be a heating engineer, and one 
in light may be no optician. The specialist 
in sound who is now coming into recognition 
more and more has not even the restricted 
range of choice given to the others cited. 
1 Journal of Bacteriology, Vol. 2, Nos. 1, 2 and 3. 
SCIENCE 
[N. S. Von. XLVIII. No. 1232 
The answer proposed to the above problem 
involves a new set of designations of the main 
subdivisions of the broad science of physics, 
designations obvious enough in themselves, 
which commend themselves as logical and ac- 
ceptable from a terminological standpoint, 
quite apart from the solution thereby offered 
of the question raised in the foregoing. It 
will be noted that the terms being derived 
from the classic Greek, are international. 
The following table will make the matter 
clear. 
Designation of 
The Science of Proposed Designation ~* = Specialist 
Mechanics Mechanology Mechanologist 
Sound Phonology Phonologist 
Heat Thermology Thermologist 
Light Photology Photologist 
Electricity Electrology Electrologist 
Magnetics Magnetology Magnetologist 
Radiation Radiology Radiologist 
A suggested sample definition is as follows: 
A mechanologist is a person who is versed in 
the science of mechanics, or mechanology, and 
who may, in addition, be skilled in applying 
the science. 
The terms proposed are so obvious that there — 
is no need to make an extended argument in 
favor of their adoption. The proposals are 
made with the thought that the need for such 
terms will become more and more evident 
through the increased entrance of physics and 
physicists into industrial and practical work, 
and it is well that a suitable terminology 
should be ready at hand for adoption as re- 
quired. 
Crayton H. SHarp 
ELECTRICAL TESTING LABORATORIES, 
New York City, 
April 24, 1918 
SCIENTIFIC BOOKS 
The Science and Practice of Photography. 
By Joun R. Rorsuck. New York, D. Ap- 
pleton and Company. 1918. Pp. VIIIT+ 
298. $2.00. 
In this book Dr. Roebuck publishes the 
course in photography which has been given 
under his direction at the University of Wis- 
consin. 
