684 
DR. C. W. SIEMENS ON DETERMINING THE DEPTH OE THE SEA 
and that Westminster is upon an inland estuary, which circumstance would exercise an 
influence in the direction of equalizing the total gravitation at Brighton and Westminster. 
Actual trial of the Instrument on hoard ship . — The foregoing may suffice to show 
what are the disturbing influences to be met with in the use of the instrument which 
forms the subject of this paper ; but it was important to ascertain what would be the 
actual indications of the instrument in taking it on board ship over seas of varying 
and known depth, in order to compare the indications of the instrument with those of 
the sounding-line. For this purpose two instruments, the smaller of which is repre- 
sented in Plate 64, were placed on board the steam-ship 4 Faraday.’ They were 
suspended in a closet adjoining the electrician’s room, near the centre of motion of the 
vessel, and were observed carefully in Victoria Docks before starting, continuously 
during the voyage, and on the return of the vessel from Nova Scotia, where it had been 
sent for the purpose of reuniting the Direct United States Submarine Cable, which had 
been fractured, where it crossed the Newfoundland Bank, by the dragging of an anchor. 
The observations during this first trial of the instrument were made by Dr. Higgs, the 
■chief of the Electric Staff accompanying the expedition. The following Table gives 
the results of these observations. 
Table I. — Bathometer Record: Steam-ship 4 Faraday,’ October 1875. 
Date. 
Hour. 
Position. 
Thermometer. 
Barometer. 
Bathometer 
Divisions. 
Depth. 
Oct. 15. 
Noon. 
Victoria Docks 
°F. 
64-5 
29-7 
Zero. 
fathoms. 
2 
18. 
Noon. 
Tidal Basin 
65 
29-95 
3'5 
19- 
8 A.M. 
Lower Fort, Tilbury... 
60 
30-00 
9-0 
19. 
10.35 a.m. 
Off Southend 
59 
29-7 
11-5 
21. 
11.45 A.M. 
Off Lizard 
60 
29-6 
47-5 
22. 
9 A.M. 
56-3 
29-5 
92-5 
23. 
Noon. 
51° 0' n.; 14° 37' w. ... 
Bad 
weather. 
By Chart. 
25. 
Noon. 
51° 25' n. ; 26' 25' w. ... 
56 
29-15 
2130 
'1900 
26. 
Noon. 
51° 7' n.; 31° 14' w. ... 
56 
29-75 
2600 
2000 
27- 
Noon. 
Dead Reckoning 
56 
29-15 
2870 
2100 
28. 
Bad 
weather. 
In this Table no correction for latitude has been made ; and although the differences 
of latitude are not very great, they would nevertheless be more than sufficient to swamp 
the results of such minute differences of depth as are met with, for instance, in passing 
from the Thames down through the Channel. The concordant results shown in the 
Table seem to prove either that the correction for latitude is (for some reason, which, 
as already stated, I am not able to explain) much less in this instrument than it would 
be in the case of pendulum indications, or that the reading of the instrument had not 
been taken with a proper degree of care. It might he assumed that the known depths 
of the channel might have betrayed the observer involuntarily into a mistake when 
observing only small divisions on the instrument, although I must personally dissent 
from such a supposition, because I entertain the highest opinion of the conscientious 
