DE. C. W. SIEMENS ON DETERMINING THE DEPTH OE THE SEA 
entirely eliminated if the spaces in the cups above and below the mercury column 
were closed against the atmosphere, and were brought into communication with each 
other. The mode of reading the instrument may also be simplified in various manners, 
or the instrument may be made self-recording by the addition of a chronograph. My 
present object has been to demonstrate the possibility of constructing a bathometer 
capable of giving indications of moderate variations in the depth of sea below a vessel, 
and to describe rather the instrument actually used than such modifications as may 
prove more advantageous hereafter. 
Practical uses of Bathometer . — The useful purposes for which a bathometer, so 
arranged as to be observable without difficulty by the commander of a ship, may be 
employed, are, I think, apparent. It often happens at sea that through clouded skies 
and fogs it is impossible for astronomical observations to be taken, and it is well known 
that the compass and dead-reckoning are very uncertain guides to the position of a ship ; 
and as the sounding-line can only be of assistance after the ship has arrived at such 
depths as are positively dangerous, many calamities are on record where, under such 
circumstances, not only sailing-vessels, but well-equipped steamers have run ashore. 
The indications of the bathometer would warn the commander of a vessel of the 
gradual approach of shallow water ; and if in possession of accurate charts, he would in 
many cases be able to determine his actual position by noting in which direction and 
at what rate the depth varies. 
Position obtained by Soundings . — An illustration from actual practice may serve to 
show how accurate a guide a knowledge of the depth of the sea can be made. In laying 
the Direct United-States Cable to America, of which operation Mr. Cakl Siemens took 
the principal charge, it occurred that, in November 1874, heavy weather had prevented 
the taking of observations for three days, when an increasing gale, and the suspicion of 
a slight fault having passed overboard, rendered it necessary to cut the cable and buoy 
the end. Before cutting the cable a sounding was taken by Sir William Thomson’s wire, 
and the depth was found to be 800 fathoms. The gale lasted several days ; and when 
the ‘Faraday’ returned to the spot where the end was supposed to be buoyed, no buoy 
could be found, and it became evident that it had been torn away from the anchor- 
chain by the violence of the gale. The sounding taken at the point where dead- 
reckoning had placed the ship at the time of buoying the cable gave a depth of 
521 fathoms, lat. 48° 32' N., long. 45° 21' W., and showed at once that the end of the 
cable must be looked for elsewhere. There exists no chart of the part of the Atlantic 
in question, giving such soundings as might have assisted in the search ; but special 
soundings were taken in all directions, from which the dip of the Atlantic basin in that 
locality could be ascertained. The cable was parted over a depth of 800 fathoms; and 
in constructing the contour-lines of the Atlantic basin in the locality, which was 
dipping towards the N.E., it became evident that in order to obtain the cable with the 
grapnel, it must be caught up in a line parallel to the contour-line, but a mile or two 
to the eastward. The expedient adopted proved successful, and the cable was recovered 
