AucustT 2, 1918] 
latter devices are far too scarce. The in- 
dustry concerned in their manufacture as 
well as the youth who may be ealled upon 
to use them, must be encouraged to the full- 
est possible extent, not only to win in the 
present war, but for the sake of the future. 
The recent condition has been aptly de- 
seribed by Professor Southall. Last De- 
eember he pointed out that the British 
navy was almost without range finders at 
the opening of the war—that almost the 
entire optical industry had to be built up 
both in France and in England since that 
time. But what is of especial interest to 
the physics teacher is his statement that, 
“if the optical industries are to be encour- 
aged and developed among us, not only now 
but in the years to come after the war, 
there will be an increasing need of trained 
and experienced men with more or less ex- 
tensive acquaintance with the whole range 
of optics, both theoretical and applied.’’?® 
Here is a demand and also an opportunity. 
Only recently has there been organized any- 
thing like a comprehensive series of courses 
in the various branches of geometrical and 
physical optics. For the first time an 
American university now offers complete 
courses in the ‘‘Theory of Modern Optical 
Instruments, Lens Design and Lens Test- 
ing, Manufacture of Optical Glass, Refrac- 
tometry, Polarimetry, Physiological Opties, 
Photometry, Spectrophotometry, Colorim- 
etry, Optometry, etc.’’** There is a new 
interest in the optics of vision due to the 
physical examination for military service, 
and at the same time we have corrective 
surgery of the eye, again based on physical 
principles.7 
But to hasten on. Smoke screens on the 
sea had no sooner begun to shut out ordi- 
nary vision than there came the suggestion 
15 Scientific American, December 15, 1917, p. 455. 
16 Scientific American, December 15, 1917, p. 455. 
17 Scientific American, January 12, 1918, p. 53. 
SCIENCE 
105 
that the use of infra-red and ultra-violet 
lenses would make photography perfectly 
possible.** Surely this involves physical 
principles of interest to the student because 
of their increasing utility, if for no other 
reason. 
New methods of photometry have had to 
be developed because of the growing mili- 
tary use of fluorescent and phosphorescent 
compounds.'® Here the Purkinje effect 
again appears. Then again, the selenium 
cell has received such study that its sensi- 
tiveness has been increased a thousand 
fold.*° Can the student escape the charm- 
ing influence of such ideas as these develop- 
ments afford? Can the teacher do less than 
encourage this interest to the fullest extent 
possible ? 
The war is responsible to a great extent 
for the fact that more attention was paid 
to illuminating engineering than to any 
other ‘branch in the leading articles in the 
most important technical periodicals in 
1917.2: Here is a great field of applied 
physics just opening up. Its demands on 
the present-day teachers are evident. Its 
opportunities need not be discussed. 
And so we could go on through the vari- 
ous divisions of physics. Under electricity, 
we meet our old acquaintance, the Hughes 
induction balance, now equally serviceable 
for locating shells buried in the earth and 
fragments embedded in the muscles of the 
human body. Coal shortage has pushed 
hydro-electric development. Food scarcity 
has aroused new interest in the electro-cul- 
ture of crops. Magnetic surveys similar to 
18 Scientific American, September 22, 1917, p. 
207. 
19 Trans. Illum. Eng. Soc., November 20, 1917, 
p. 394, Jllum. Eng. (Lond,), March 1917, p. 
76. Rep. Nat. Phys. Lab., 1915-16, p. 33. 
20 Trans. Illum. Eng. Soc., XII., 8, November 20, 
1917, p. 395. 
21 Trans. Illum. Eng. Soc., XII., 8, November 20, 
1917, p. 117. 
