14 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
Among other topics, the question of the effective ventilation of 
buildings has been given attention, and initiative steps have been 
taken to learn what investigators are making a serious study of this 
important subject. The vitiation of the exterior atmosphere in 
closely settled localities is also recognized as a question of great im- 
portance to the dwellers in cities, and an effort is making through the 
publications of the Hodgkins fund to disseminate the results of late 
noteworthy investigations in this connection. 
The application of atmospheric air to therapeutics has received 
consideration, and while no research having for its object the direct 
‘use of the atmosphere as a curative agent has, as yet, been aided, the 
work furthered by the fund, excepting that which deals almost ex- 
clusively with the mechanics of the atmosphere, is closely related to 
medicine and hygiene. Consequently the reports of investigations 
and experiments prosecuted in widely separated localities, such as 
London, South Africa, Paris, and the cities of our own country, 
have been followed with interest, in common with all classes of 
research which make broader the way for the practical utilization of 
our knowledge of the nature and properties of atmospheric air for 
the welfare of mankind. 
ABSOLUTE MEASURE OF SOUND. 
The research of Dr. A. G. Webster, of Clark University, on the 
absolute measure of sound, which was aided again during the present 
year by a moderate grant from the Hodgkins fund, is reported as 
advancing satisfactorily toward completion. The instruments pre- 
pared especially for use in this research are expected to prove of 
service in solving many practical questions relating to sound, such, 
for instance, as the testing of sound-proofing materials, or of audible 
signals. In conducting the investigation many delicate points in the 
theory of such instruments have been settled by actual experiment, 
so that, in some particulars, the experimental knowledge is in advance 
of the present mathematical theory. 
The manuscript describing the methods and results of this research 
will be submitted to the Institution for publication when completed. 
PROPERTIES OF MATTER AT VERY LOW TEMPERATURES. 
The investigation of the properties of matter at very low tempera- 
tures, involving the use of liquid air, in aid of which a grant was 
approved in 1906, from the Hodgkins fund of the Institution on 
behalf of Prof. E. L. Nichols, of Cornell University, has been 
steadily progressing. The research is now to enter on a careful study 
of the index of the refraction of gases, and gaseous mixtures and va- 
pors, over extreme ranges of pressure of temperature. The effect on the 
