28 
CHEMISTRY: D. P. SMITH 
Proc. N. A. S. 
companying the isostatic adjustments may be a partial cause. Material 
is moved in this process, to zones of decidedly different temperatures, to 
hotter or to colder zones, and it seems to be logical to conclude that some 
chemical or physical changes may take place which would affect the density 
of the material transported. In the process of isostatic adjustment all 
the material of a column above the zone of flow is raised or lowered. The 
ordinary thermal expansion of the material of a column, as it changes its 
temperature, is capable of accounting for only a small part of the changes 
in the length of a column. 
It should be clearly borne in mind that the theory of isostasy does not 
explain any vertical movements other than those necessary to maintain 
equilibrium. Some other theory is needed to explain elevation and subsi- 
dence and the writer feels that the theory of local expansion and contrac- 
tion is in general in harmony with the geodetic data. He believes, however, 
that there are local vertical movements of small amounts which may not 
be due to these causes. 
It is hoped that increased activity will take place in collecting geodetic 
data and in extending the investigations in isostasy. It is particularly 
desirable that we have the investigations include the ocean areas as soon 
as geodetic data may be available within them. 
1 See page 90, "Investigations of Gravity and Isostasy," Spec. Pub. No. 40, U. S. Coast 
and Geodetic Survey, 1917. 
2 "Strength of the Earth's Crust," by Jos. Barrel!, J. Geol., January-February, 
1914 (48); and "Discoidal Structure of the Lithosphere" by Bailey Willis, Bull. Geol. 
Soc. Amer., June 30, 1920. 
3 "Investigations of Gravity and Isostasy," Spec. Pub. 40, U. S. Coast and Geodetic Sur- 
vey, pp. 70-82. 
4 "Investigations of Isostasy in Himalayan and Neighboring Regions," Professional 
Paper No. 17, by S. G. Burrard, former Surveyor-General of India, 1918. 
EXPERIMENTS ON THE ELECTRICAL CONDUCTION OF A 
HYDROGEN ALLOY 
By Donald P. Smith 
Chemical Laboratories, Princeton University 
Communicated by O. Veblen. Read before the Academy, November 17, 1920 
In studies which were described some time since 1 it was found that 
hydrogen, when discharged electrolytically upon any one of certain metals 
which occlude it, produces a temporary diminution in the electrical re- 
sistance of the metal. With metals, such as palladium, which occlude 
large amounts, and suffer, as has long been known, a lasting increase of 
resistance, the diminution of resistance, or supplementary conductance, 
is superimposed upon the opposite and more enduring effect; while in the 
