Feb. 23, 1882 | 
NATURE 
387 
Dr. Jacobsen, the chemist of the Pomerania Expedition, 
has the merit of being the first to have rendered practic- 
able the carrying out of such operations as the extraction 
of the gases and the determination of the carbonic acid 
in sea-water at sea. In subsequent expeditions his 
apparatus has been used with but slight modifications. 
His apparatus for extracting the oxygen and nitrogen was 
used on board the Challenger and by Dr. Tornoe without 
alteration ; the method of determining the carbonic acid 
was modified both on board the Chadéenger and on the 
Norwegian expedition. 
In the first chapter, ‘‘(n the Air in Sea Water,” Dr. 
Tornoe describes the apparatus used for obtaining samples 
of the water at different depths. In principle it resembles 
most other instruments devised for the same purpose, 
consisting of a tube which is open at both ends while 
descending, thus allowing the water to pass freely through 
it. On reversing the motion, the two ends are closed by 
conical valves worked by screw fans. In construction, 
however, it differs widely from other instruments of the 
same kind. Instead of being straight the tube, which forms 
the body of the instrument, is spiral, and holds about 
five litres. The diameter of the tube is 5°5 centimetres, 
and the external diameter of the spiral is 33'5 cm., the 
total length of the instrument over all being 144 cm., or 
nearly 5 teet. These measurements are taken from the 
plate accompanying the book, and it is apparent from 
them that the instrument is one of very considerable size ; 
it is a pity that its weight is not given. Both ends of the 
spiral tube have conical valve seats, the smallest diameter 
of which is equal to that of the tube. The valves fitting 
these apertures are kept open during descent by the 
action of screw-fans, which turn in one direction during 
descent ; when the direction of the motion is reversed 
and the ascent commenced, the first few turns of the 
screw-fans are used for bringing the valves close to their 
seats, when, being released from the screws, they are 
pressed home bya pair of spiral springs. In order to 
do the necessary work on the screws, the instrument has 
to travel through about seven fathoms of water. The 
water, therefore, which it brings up will be a far average 
sample of the particular seven fathoms through which it 
was drawn. ‘The instrument appears to have given great 
satisfaction, and it has many good points in its construc- 
tion. The spiral form of the tube is an ingenious con- 
trivance for increasing its capacity without unduly length- 
ening the whole apparatus, but the spiral form also pro- 
duces an increased resistance to the passage of the water, 
so that what passes through will lag behind what passes 
outside the instrument. Hence the sample actually inside 
the tube at any moment is a sample of the watera certain 
number of fathoms above it, and not of the water in the 
centre of which it is plunged. For ocean work this is 
not a serious drawback, and it is in a great measure cor- 
rected by the necessity for hauling it backwards through 
seven fathoms of water before it is closed. The arrange- 
ment for working the valves is very ingenious, and permits 
the use of several instruments on one line, for the instru- 
ment requires to traverse seven fathoms of water in order 
to close, and this is much more than would be traversed 
by it with the line held fast and exposed only to the roll- 
ing motion of the ship. This advantage, however, is 
rendered nugatory by the great size of the instrument, as 
one of them would be a sufficient load for anyline. It is 
evident that for taking samples at small intervals of depth 
as every five fathoms, the instrument would have to be 
modified, or one of the other existing forms used ; but 
for the collection of the samples which actually were 
taken, the instrument was quite satisfactory. Its inventor 
was Capt. C. Wille of the Norwegian navy. 
The apparatus used for boiling out the gases is exactly 
that recommended and figured by Jacobsen in Liebig’s 
Annalen, vol. 167, p. 1. It consists of three parts—a, 
the flask for the reception of the sea water to be boiled, 
its capacity is about goo cub. centims. ; 4, the bulb tube, 
fitted into the mouth of the flask by an india-rubber cork, 
which, with the tube, forms a most ingenious kind of 
slide-valve, enabling connection between the flask and 
the remainder of the apparatus to be made or broken at 
will. This bulb-tube serves a double purpose : at first it 
contains a supply of distilled water, which, being con- 
verted into steam, drives all the air out of the upper part 
of the apparatus, and so enables a vacuum to be formed ; 
in the latter part of the operation it serves for the recep- 
tion of the sea water which expands into it out of the 
flask during the process of boiling. The third part of the 
apparatus, c, is the gas-tube in which the sample of gas is 
sealed up and preserved when it has been extracted from 
the water. This tube, which ought to have a capacity 
of about 60 or 70 cub. centims., resembles a pipette 
whose end-tubes are reduced to a length of 5 or 6 centi- 
metres, and are contracted to a very small diameter near 
the body. It is attached to the bulb-tube by a piece of 
good india-rubber tubing, care being taken that the ends 
of the two tubes abut. By the boiling of the distilled 
water in the bulb-tube at the commencement of the 
operation all the air is expelled, and the apparatus her- 
metically closed by sealing up the gas-tube at the con- 
traction at its upper end. During this operation commu- 
nication is interrupted, by means of the slide-valve, 
between the flask and the bulb-tube. After the upper 
end of the gas-tube has been closed, communication is 
re-established, and the water in the flask now finds itself 
exposed to the action of a tolerably good vacuum, and in 
consequence the air dissolved in it immediately begins to 
be disengaged ; this is assisted by heating in a water- 
bath. When it is judged that the air has all been ex- 
pelled from the water, the flask is again isolated by means 
of the slide-valve, and the gas-tube sealed up at the 
lower contraction and preserved for analysis. As there 
is always some of the gas remaining in the bulb-tube, the 
space so occupied is measured and noted, so as to be 
taken into account in determining the total volume of gas 
per volume of water. The beautiful part of this appa- 
ratus is the slide-valve arrangement, which was invented 
by Dr. Behrens of Kiel. Otherwise the apparatus does 
not differ from that described by Bunsen, and used by 
him in Iceland. Had it, however, been necessary to use 
Bunsen’s apparatus unmcdified, it may safely be assumed 
that we should now have very few analyses of the air dis- 
solved in sea water. It is Dr. Behrens’ invention which 
renders the operation, sufficiently easy to enable it to be 
carried out successfully asa matter of routine at sea. 
There is another item in the construction of the instru- 
ment which, though apparently insignificant, is really of 
the utmost importance in insuring a successful result—it 
is the way in which the contraction in the two end tubes 
of the gastube is made. The tubes supplied to the Nor- 
wegian Expedition seem to have been much the same 
as those supplied to the Challenger. Both came from 
Thuringia in Germany, and in the Chad/enger ones the 
contraction was formed by thickening up the tubes before 
the blowpipe, so that the external diameter was not dimi- 
nished, while the internal diameter was reduced often 
beyond what was necessary. Now in attempting to close 
the tube with the blowpipe at one of these thickened con- 
tractions, the thin and comparatively wide tube on either 
side of the thick contraction is very aft to be heated up to 
softening point before the much more massive contraction 
has got even hot. In the inside of the tube, however, 
there is, even after the boiling, a much lower pressure 
than in the outside atmosphere ; consequently, immedi- 
ately the tube next the contraction gets soft, it falls in, and 
though the tube may be drawn out, and so appear for the 
moment to be satisfactorily closed, the point so formed 
never fails to crack on cooling. This is the reason of the 
deplorable lors of as much as 75 per cent. of the gas 
samples boiled out by Dr. Tornoe on his last voyage. A 
