THE TENDENCY OF METHODS FOR THE MEAS¬ 
UREMENT OF THE FORCE OF GRAVITY 
ON THE OCEAN. 
BY 
G. W. Littlehales. 
Considering the degree of advancement that has been 
reached in the adaptation of instrumental means to the 
necessities of gravitational research on the land, it is worthy 
of remark that no beginning has yet been made in gather¬ 
ing the observations that will reveal a knowledge of the 
variations of the force of gravity over the oceanic areas of 
the globe. 
Even under exceptional circumstances of calm at sea, the 
unsteadiness of the observing platform and the consequent 
effect upon the inertia of masses are such as to preclude the 
application of methods depending upon the measurement 
of the time of flight of a plummet, or the oscillation of a 
pendulum, or the changing relation with change of locality 
between a given mass and its weight. Experiments, which 
have fallen short of success, were undertaken with a view 
of examining into the possibility of using the Electric Clep¬ 
sydra for the measurement of relative qualities of mercury 
discharged in the same interval of time at different locali¬ 
ties through an orifice in the bottom of a vessel of compar¬ 
atively large cross-section (U. S. Naval Ordnance Papers, 
No. 4). Such an apparatus has been in satisfactory use for 
the measurement of minute intervals of time at stations 
where the force of gravity has been accurately determined, 
and, being swung in gimbals from the beams of a ship, ap¬ 
peared to need no modification beyond the inclusion of a 
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