462 
THE TROPICAL AGRICULTURIST. [January t, 1890. 
a deposit consequently takes place on the inner sur- 
face oi the globe. This, however, does not affect the 
power of the lamp untd after four or five hours' use, 
and can easily be removed when new carbons are sup- 
plied. Arc lamps can be made so as to burn in any 
position, and the additional initial cost being small 
relatively to the increased power, such a lamp would 
appear to be preferable to the incandescent lamp. It 
is a question, however, how tar an electric light would 
assist an observer at the surface in making observations 
ot objects at the bottom of the sea. On dark nights 
it would no doubt be extremely useful, but in the day 
time the difficulty of accurately observing objects at 
any considerable depth in ordinarily clear water is 
caused, not by the insufficiency of fight, but by its 
refraction aud reflection, a difficulty winch is increased 
where the surface is not calm. This difficulty can be 
obviated by the use of a water telescope, but the ob- 
jection to the use of this instrument is that it is not 
easily used except in fairly calm water, and that the 
actual area in view at any given moment is of course 
limited by the "hold " ot tne glass. Where the water 
is at all thicK the water telescope is useless (at any 
rate at any considerable depth;, and the use of the 
electric light would probably then be lound of 
no help to it whether by day or by night. Given 
clear water, on the other hand, the electric light 
would no doubt prove of great value in facilitat- 
ing observations ac night, when it would pro- 
bably be found that the use of the water telescope 
coma be dispensed with. This would almost cer- 
tainly be the case in a 'calm sea, aud in the absence 
of moonlight, aud it is probable that even on moon- 
light nights and with a ruffled surface, the illumina- 
tion ot tne bottom by a powerful lamp would be suffi- 
cient to counteract liie effects of reflection (though 
hardly of retraction) without the help ot the water 
telescope, i venture to suggest thatthe observations 
which the Go /eminent of Madras desire to make upon 
the nab. ts of the pearl oyster would be greatly facili- 
tated by the employment 01 a diver equipped with an 
ordinary diving dross. By tnis means a prolonged 
stay could be male by an observer on the sea bottom 
who could not oniy mane an accurate survey of the bed, 
but could periodically examine the same ground, select, 
specimens and make minute observations, whicb would 
b^ impossible to an observer at the surface, aud are 
equally impossible to a native diver, whose stay at the 
bottom is limited to a minuie or so. The use ot a 
diving dress, in conjunction with the eltctne light, 
would render tbe observer almost independent ot the 
transparency of the water aud of day or night. 
Lord Gross writing on 7th March of this year 
stated ; — 
It will be observed that the opinion of the United 
States Oommissioner of Fish aud Fisheries practically 
coincides with wbat of the other experts, being, in 
effect, that the utility of the electric light for the 
purpose in view is doubtful, but that such a light 
would be usef ul to a diver. Tne iniorinatiou obtained 
seems not to afford much encouragement for pursuing 
the inquiry further. 
Amongst the enclosures was 
A letter from the United states Commissioner of 
Fish and Fisheries to the Secretary of State, relative 
to exptnmeuts in submarine investigations made by 
officers of the United dtates Fish Uouiinisaiuu Steamer 
"Albatross," together with a report on the construction 
and outfit of that vessel by Lieutenant Uommander 
Ta'iner, of the United States Navy. 
The Commissioner stated:— 
In order to test the usefulness of electric light in 
connection with suomarine work, from both a practical 
and a scientific standpoint, the Fish (Jominission 
Steamer "Albaiross" was supplied with a complete 
electric plant, according to the L'dison incandescent 
8VBtem, and with sufficient power to work also two or 
three arc lights in circuit witu the smaller lamps. 
This plant was lully described in a report prepared by 
Lieutenant Couimauder Z. L. Tanner, United Stales 
Navy, commanding the steamer "Albatross," and a 
copy of the same is herewith respectfully transmitted. 
About a year ago smaller and improved forms of 
dynamo and engine were sabstituted for the original 
ones. This plaut provided for the lighting of the entire 
ship, as well as lor submarine illumination, aud its 
coat was much greater than would be that of a smaller 
outfit intended for the latter purpose only. Moreover, 
our experience would indicate that the electric light 
is entirely uusuited to the researches described in 
L >r& Salisbury's letter, namely, to study the habits of 
the pearl oyster iD depths of 10 to 12 fathoms from 
the deck of a vessel. 
The submarine light of the steamer " Albatross," 
as originally constructed, consisted of three Elison 
incandescent lamps fixed to a brass plate which latter 
formed the base of a double glass globe envtloping 
the lamps. It worked well down to a depth of about 
20U feet, below which the fastenings of the globe were 
unable to withstand the pressure of the water. Since 
tbe first year from one to three unprotected Edison 
lamps have generally been employed, and have been 
successfully iowered to a depth of 150 feet, though 
seldom used below a few feet in depth. The greatest 
depth at which the light can be seen varie3 with the 
clearness cf the water, but under ordinary circumstances 
it disappears below 60 or 70 feet. Objects swimming 
in the water about the lamps cannot be distinguished 
at that depth. One of the most favourable opportunities 
for testing the efficiency of the lamp below the surface 
occurred among the Bahamas islands, where the 
"Albatross" usually anchored in depths of 30 to 40 
feet. The water there was clear, and the bottom con- 
sisted of white coral sand. When the lamp was 
lowered upon such bottom it could be plainly seen, 
and also the position of all dark objects near it, but 
the character of the latter could not be determined 
from the steamer's deck. The lamp is now seldom 
employed except within a foot or two of the surface 
where it serves to attract some kind of fishes, and 
other marine forms, which may then be captured in 
nets or by means of hooks. I would suggest, how- 
ever, that the electric light might bp utilized to illu- 
minate the beds of pearl oysters so that the observer 
making use of the diving bell could readily study the 
habits of that molluse, I do not believe that it could 
otherwise be made of any service in that connection. 
On 28th March of this year Lord Cross wrote : — 
It will be seen that tbe results obtained from the 
Amiralty experiments continue to afford little reason 
for thinking that the electric light could be success- 
fully used for the purpose in view, even in conjunction 
with a diver. A 2,000-candle power arc lamp, taken 
down by a diver, rendered articles on the sea bottom 
visible at a distance of not more than about three 
yards from the bull's eye of the lantern. 
The letter from the Admiralty stated : — 
From lamp of 2,00 )• candle power, burnt from a 
Siemen's dynamo, with a current of about 35 amperes, 
could see an article on the bottom in 6£ fathoms at 
a distance of about three yards from the bull's eye of 
the lantern. A 50-candle power incandescent lamp 
used under similar circumstances in clear water enabled 
objects to be seen 2 or 3 feet from the light. 
Further experiments made in the present year at 
night at Spithead indicate that the shape of a white 
object may be distinguished from the surface at a 
depth of 8 feet when a 50-candle power incandescent 
light, fitted in a tube with a glass bottom, so that 
its rays were projected downwards, is lowered to with- 
in a foot or two of it. The white color could be 
seen at 12 feet, and the reflection of light in the 
water when the lamp passed directly over it at con- 
siderably greater depths, the water being 16 fathoms 
deep. It appears probable from these results that, in 
perfectly clear water, and using a powerful light, 
objects might be distinguished at a slightly greater 
depth at night than under favourable circumstances 
in the day time. 
The lamps used were of no service in daylight. 
The Madras Board of Bevenue thereupon recorded 
a resolution— dated 28th May 1889 :— 
The papers on the use of electric lighting for deep 
sea-working will be returned to Government with the 
letters and notes furnished by Messrs. Thurston 
