OoroseER 11, 1918] 
SCIENCE 
375 
would be much better to make it 180° from 
the ends of a vertical diameter. The film of 
gelatine (conveniently bent in form of an open 
cylinder and fastened with a little wax) is 
shown at g. The mantel contained about 
313 sq. em, of area and the film was less 
than .1 mm. thick, weighing about .4 gram. 
As the observations contained in Fig. 2 are 
tentative, I merely chalked a centimeter scale 
increasing downward on the strip fg, to 
specify the position of the index. If absolute 
data were to be reached, the scale would, of 
course, have to be graduated in terms of 
(0,-0) sec 6 where @ is the variable angle 
measured in a given direction from the hori- 
zontal diameter of fh; or a torsion head could 
be provided at b. Fig. 2, in which the posi- 
tion of the pointer d, on successive days are 
laid off vertically, the curve rising as the 
weight of the gelatine increases, is sufficiently 
interesting without this and I merely placed 
the apparatus (without a case) in a quiet 
corner free from draft and read off the centi- 
meters from across the room. It is in fact 
fascinating to watch it from day to day; for 
the play of the pointer, in spite of the handi- 
cap of leaverage, is over 40 em. along the strip. 
The lowest position occurred during the rela- 
tively cool weather following August, 15. 
After that the weight increased until the 
very muggy weather at M toward August 25 
was passed through. With the arrival of a 
cold wave the weight drops almost suddenly, 
to increase again with equal abruptness to 
