652 
able in multiples of the main current, was 
sent through the fixed coil, and the main 
current through the other coil. The deflec- 
tion of the electro-dynamometer gave 
means of computing the magnitude and 
phase of the different components. 
Very interesting papers were read by Dr. 
N. E. Dorsey, on the determination of sur- 
face tension of water and of certain aque- 
ous solutions by the method of ripples ; by 
Professor Frank EK. Bigelow, on the series 
of international cloud observations made 
by the United States Weather Bureau; by 
Professor C. F. Marvin, on kites and their 
use by the Weather Bureau in the explora- 
tion of the upper air, and by Mr. B. B. 
Brackett, on the effects of tension and 
quality of the metal upon the changes in 
length produced in iron wire by magnetiza- 
tion. 
Professors E. W. Morley and D.C. Miller 
presented a joint paper on the coefficient of 
expansion of certain gases. As the coeffi- 
cient of expansion of hydrogen has been 
determined by the International Bureau of 
Weights and Measures at Paris, with a very 
high degree of precision, that of other gases 
may be determined by comparison. The 
method used in these experiments is a dif- 
ferential one, in which the difference in the 
expansion of oxygen and hydrogen, for ex- 
ample, can be determined with accuracy. 
Hydrogen is placed in one globe of five 
liters capacity and oxygen in a similar 
globe. These globes are connected to a 
manometer. They are first surrounded 
with melting ice, and then with steam. 
The differential expansions are readily ob- 
served. In this way the coefficients of ex- 
pansion of four gases have so far been deter- 
mined as follows: 
Canbony Dioxide eerste ee 0.0037122 
INDELOBEN Se eaccecseceucetsencetsrorneeasres 0.0036718 
WANE eieecenesect cee seas eaneeaneneeecroseabes 0.0036719 
(Ob:gAE2)Tascosagdnoco90q.00sN00deC00000000" 0.0036729 
A Note on the Construction of a Sensitive 
SCIENCE. 
[N. 8S. Vou. VI. No. 148. 
Radiometer was read by Professor Ernst 
Fox Nichols. In this paper the construe- 
tion of a new form of compensating torsion 
radiometer, used recently in a number of 
researches in the remote infra-red spectrum, 
was described in detail. The instrument 
is capable of a higher degree of sensitive- 
ness than either the spectro-bolometer or 
linear thermopile. A steadiness of action 
and freedom from extraneous disturbances, 
when working at high sensitiveness, are 
secured by means of the compensating ac- 
tion of two precisely equal vanes sym- 
metrically mounted on either side of the 
axis of a quartz fibre suspension. ‘The 
system, in consequence, is acted upon dif- 
ferentially by all accidental disturbances, 
while rays to be measured are concentrated 
upon one of the vanes. The degree of sen- 
sitiveness actually attained in one instance 
was so great that the influence of rays from 
a single candle at a distance of one-third of 
a mile could be detected and roughly meas- 
ured. With an instrument of this kind 
Professors Rubens and Nichols have recently 
discovered heat waves one-fortieth milli- 
meter in length, and have demonstrated 
their electro-magnetic character. 
Professors EH. L. Nichols and EH. Merritt 
presented a paper on the photograph of 
manometric flames. The photographs were 
taken on a revolving drum of sensitized film, 
and showed in a striking way the effects of 
various sounds. Words and short phrases 
were spoken before the receiver. It was of 
interest to note that the effects of nearly 
like sounds could be distinguished in the 
photographs. The paper was illustrated 
with many lantern slides. 
Professor Carl Barus read papers on the 
rate at which hot glass absorbs superheated 
water, and on a method of obtaining capil- 
lary canals of specified diameters. In the 
former he computed from experiment that 
there is an absorption per hour of 0.025 
cm.’ of liquid water per em.” of glass sur- 
