THE PRESIDENTIAL ADDRESS. vf 
a correction has, in some way, to be applied. Recently, Dr. Victor Meinesz, 
of the Dutch Survey, who has carried out an extensive gravity survey in 
Holland, has sought to minimise this effect by the use of pairs of pendulums 
swinging in opposite phases, and so reacting on the support in opposite 
senses. This has opened out a prospect of accurate gravity determinations 
at sea. The use of a pendulum method on a surface vessel is hardly 
possible, but a submarine when sufficiently immersed offers comparative 
tranquillity, and it is hoped that the small residual horizontal motions may 
be capable of elimination, and the diminished vertical oscillation allowed 
for. The methods previously employed at sea which could claim any 
accuracy are those of Hecker. In one method, the pressure of the atmo- 
sphere is found in absolute measure from the boiling point of water and 
compared with the gravitational measure afforded by the barometer. In 
a more recent method, also devised by Hecker, and followed with some 
modifications by Duffield, the idea is to carry about a standard atmosphere, 
i.e. a mass of air at constant volume and prescribed temperature, whose 
pressure is measured gravitationally by the barometer. Both methods are 
highly ingenious, but cannot compete as regards accuracy with the 
pendulum method if this should be found practicable. 
It is a matter of regret that the observational side of Geophysics has, 
of late, been so little cultivated in this country. In India with its wide 
opportunities, geodetic and gravitational work has long been carried on 
with high efficiency, and has furnished essential material for the general- 
isations I have referred to. But in the Home country, although we have an 
admirable topographical survey—whose headquarters by the way are here 
in Southampton—nothing so far as I know has been done towards a gravity 
survey since the time of Kater, more than a century ago. Proposals for 
the establishment of a formal Geodetic Institute, such as existed in some 
other countries before the war, which should embrace this as well as other 
subjects, have been urged, but have had to be abandoned owing to the 
exigencies of the time. It is therefore some satisfaction to record that 
a modest beginning has been made at Cambridge by the institution of a 
Readership in Geodesy, and that when the requisite pendulum outfit is 
complete, it is hoped that a gravity survey of these islands may be initiated. 
The physical features are hardly so rugged that sensational results such as 
were found in India are to be expected, but it is desirable that the work, 
which will involve comparatively little labour and expense after the 
initial steps, should be carried out. The example of Holland shows that in 
a country which has no outstanding features at all a survey may reveal 
