692 
DR. C. W. SIEMENS ON DETERMINING THE DEPTH OF THE SEA. 
advantageous use of the instrument, would serve, on the contrary, to increase its measure 
of usefulness in the hands of the navigator. 
In the Addendum to my paper of the 23rd February, I described a modification of 
the principle of the bathometer, designed for the purpose of measuring horizontal 
attraction ; and I take this opportunity of stating that I have constructed an instrument 
of this description, which has been erected upon a solid foundation at the Loan Exhi- 
bition, South Kensington. The measure of sensitiveness of this instrument is given by 
the fact, that the weight of a person stepping from one side of it to the other causes 
the indicating bubble to travel through one division (of 1 millim.) of the scale. It 
would not be difficult to construct such an instrument of still greater sensitiveness ; 
and I believe that it could be made a useful adjunct at physical observatories, for the 
observation of diurnal changes in the horizontal attraction produced by the sun 
and moon as well as of terrestrial causes of disturbance of the superficial equilibrium of 
the earth. 
