734 SCIENCE. 
the last column is obtained by adding the 
intensities for the five kinds of plates and 
asingle diamond. Similarly the last row 
represents the intensities corresponding to 
all the diamonds and one kind of glass. 
-The table shows that the fluorescence de- 
pends upon the kind of glass, and also upon 
the particular diamond used. One would 
expect the former, and one might not be 
surprised that the black amorphous dia- 
monds do not act as do the clear crystalline 
stones. But that the latter differ among 
themselves is strange. It was thought 
that the difference might be due to differ- 
ences in shape and the character of the 
-seratch. This conclusion was rejected when 
it was found that diamond No. 4 would 
always fog the plate, even when the sur- 
._ face of the plate was not scratched at all. 
When the diamond was held out of cutting 
position and drawn across a plate, a dark 
band appeared on development. Diamonds 
Nos. 5 and 6 could scarcely be made to fog 
a plate, however they were held. 
That friction has much to do with fluores- 
- cence was shown by the fact that some- 
times a dark band would be discontinuous 
_in two or three places along a diamond 
scratch. 
The band produced by No. 4 was so 
strong that it was thought the fluorescent 
light might be visible. This proved to be 
true. When the eye was rendered very 
sensitive by being in absolute darkness for 
an hour, the conclusions drawn from the 
table were verified directly. The fluores- 
cence from No. 4 was very marked, espe- 
cially when English or white crystal glass 
was used. No visible fluorescence could be 
obtained with any of the black diamonds. 
To test the equation b=2¢. tan 7 a dry 
plate was laid on a table, film upward. A 
plate of clear glass was then laid on the dry 
plate and a diamond was drawn across the 
clear plate. The mean of several measure- 
ments of b and ¢ gave a critical angle of 
(N.S. Vou. XIII. No. 332. 
about 39°. For the particular plate used, 
this was approximately the critical angle 
for yellow light, showing that, whatever 
other wave-lengths might be present the 
longest waves that affected the film were 
those of yellow light. This conclusion was 
strengthened by the fact that, to the eye, 
the light appeared to be a greenish yellow, 
and that orthochromatic plates were much 
more sensitive to it than ordinary plates. 
Measurements of 6 and ¢ for plates of 
various thicknesses gave values of 7 rang- 
ing from 38.6° to 40.4°. It would seem 
that the fogged band should be much 
broader when the dry plate itself is 
scratched, for then the critical angle is 
determined by the ratio of the indices of 
refraction of gelatine and glass. Measure- 
ments did not confirm this point, though 
they showed a constant ratio between 0 
and ¢. 
ArrHur L. Foiey. 
PHYSICAL LABORATORY, 
INDIANA UNIVERSITY. 
HOW .BOTANY IS'STUDIED AND TAUGHT IN 
JAPAN. * 
MoprErn botany was practically intro- 
duced into Japan twenty-four years ago by 
the late Professor Yatabe,; who studied 
botany at Cornell University, graduating 
in 1876. He became the first professor of 
botany at the Imperial University of Tokyo. 
Before him there were several botanists in 
Japan who studied the native plants quite 
thoroughly. But most of them being am- 
ateurs, did not know much about mod- 
ern botany. Some of these old botanists 
still live. The well-known Dr. Keiské Ito, 
who was the Director of the Botanical Gar- 
‘den of the University before Professor Ya- 
* A paper presented at one of the Botanical Semi- 
naries, Cornell University, November, 1900. 
+ Professor Yatabe was drowned in the sea at Kam- 
akura not far from Tokyo in August, 1899. 
