March 2, 1882 | 
NATURE 
413 
different temperatures cannot be precisely stated, the 
Challenger results leave no doubt that more carbonic 
acid is absorbed the lower the temperature is. Taking 
the mean of all the Cadlenger determinations in surface 
water at temperatures between 10°C. and 15° C., we have 
43°5 mer. per litre of carbonic acid liberated by boiling 
to nearly dryness after precipitation of the sulphates ; 
and this agrees to a fraction of a milligram with Tornoe’s 
average amount of carbonic acid present as bicarbonate. 
Dr. Tornoe concludes this part of the work with an 
interesting inquiry into the condition in which the car- 
bonic acid exists in the water, and comes to the conclu- 
sion that it is probably present in combination with soda, 
forming bicarbonate of soda. 
In the third portion of his work Dr. Tornoe gives an 
account of his experiments on the amount of salt held in 
solution by the sea water. For determining it he follows 
two methods, the one depending on the specific gravity, 
and the other on the chlorine contained in the water. 
The specific gravity was determined by means of suitable 
glass hydrometers, and the chlorine by means of silver 
solution of known strength. In order to reduce the 
specific gravities which were observed at various temper- 
atures to their value at one standard temperature, Dr. 
Tornoe reports an elaborate series of experiments on the 
expansion of sea water due to change of temperature, and 
he uses the results so obtained along with those of Ekman 
for reducing his results. They are given in two columns ; 
in the one is the specific gravity at 17°5° C. referred to 
that of distilled water at the same temperature as unity ; 
in the other they are reduced to their value at the tem- 
perature of the water when zz sz¢u, referred to distilled 
water at 4° C. as unity. 
In order from these results to arrive at a knowledge of 
the amount of solid matter dissolved, he makes a series 
of careful determinations of solid residue of chlorine and 
of specific gravity in seven samples of water. He finds 
that “‘the co-efficient of chlorine may be taken at— 
1°809 + 0°00076 
with a probable error in a single determination of + 
0’002, and the co-efficient of specific gravity at— 
131°9 + 0'058 
with a probable error in a single determination of £o'r5.” 
The specific gravity is here taken at 17°5° C., and the 
unit is that of distilled water at the same temperature. 
The determination of the solid residue in sea-water 
presents special difficulties due to the presence of so 
jarge amounts of magnesia salt. These difficulties are 
overcome in an ingenious way :—“ From 30 gr. to 40 gr. 
of sea-water were introduced into a thick porcelain crucible 
of known weight furnished with a tight-fitting cover, and 
evaporated on a water-bath. So soon as the salt was 
sufficiently dry the crucible with the cover on was 
heated for about five minutes over one of Bunsen’s gas- 
burners, then cooled and weighed with its contents.” 
The free magnesia liberated by this process was then 
determined by dissolving the salt and adding a quantity 
of titrated sulphuric acid and determining what remained 
unneutralised by titrating with caustic soda. 
The results so obtained are given in a table, and also 
represented graphically in charts at the end of the work, 
These charts show very clearly the distribution of the 
water from the Atlantic amongst that coming from Polar 
regions, which is also confirmed not only by the tem- 
peratures observed, but also by the distribution of 
nitrogen dissolved in the bottom water, of which Dr. 
Tornoe has given a chart. It is well known that the 
water coming up from the North Atlantic is much salter 
than that coming south from the Arctic and Polar 
regions. From the variations in the amount of salt found 
in the bottom water of different districts Dr. Tornoe 
suspected that some of it must be due to the presence of 
Atlantic water which had got cooled on its way north, 
and had sunk to the bottom. It is in the highest degree 
probable that the nitrogen found dissolved in a sea-water, 
taken from any depth, is the nitrogen which it took up 
when last exposed tothe atmosphere. Nowthe amount of 
nitrogen which it would take up would depend to a great 
extent on the temperature, so that water which had been ex- 
posed at the surface in Arctic regions would take up more 
nitrogen than water which had been exposed in tem- 
perate regions, so that the amount of nitrogen present, 
for instance, in a bottom water, may be taken to indicate 
the temperature which the water had when last exposed to 
the atmosphere. Now it is a remarkable result of Dr. 
Tornoe’s investigations that where he finds a high per- 
centage of salt in the bottom water he also finds a low 
percentage of nitrogen, and vice versd, rendering it in 
every way probable that the areas which he has mapped 
out are really supplied on the one hand from the Atlantic, 
and on the other from the Arctic Oceans. This result is 
a further evidence of the importance of accurate deter- 
minations of the gaseous contents of sea-water. 
It is impossible to conclude this notice without con- 
gratulating the Norwegian nation on the advanced 
position which it has taken up in ocean exploration 
and the success which has attended the labours of its 
servants, and in an especial way of Prof. Mohn and those 
associated with him in the three summer trips of 1876, 
1877, and 1878. Not only is the work done great in 
amount and of the highest scientific interest, but it has 
been published with a praiseworthy expedition which 
adds immensely to its present value. 
J. Y. BUCHANAN 
COMET f 1881 
O* the morning of October 4, 1881, while engaged in 
sweeping the eastern sky for new comets, I found 
an object about 10 degrees preceding a Leonis on the 
ecliptic which bore a strong resemblance toa bright round 
nebula, with a marked condensation in the centre. I 
roughly estimated the position of the object, and referring 
to Herschel’s catalogue of nebulae, endeavoured to iden- 
tify it, but without success. Then carefully noting its 
place relatively to the small stars in the same field of my 
Comet f 188r, October 3, 15h. 15m.; to-inch reflector, power 25. 
10-inch reflector, I resumed sweeping in the region near. 
About half an hour later—3 45 a.m.—I re-observed the 
object, as clouds were rapidly coming up. A slight motion 
to the eastward was at once suspected to have occurred 
in the interval, but my positions were merely eye estima- 
tions, and I distrusted them though feeling certain at 
the time that the supposed displacement was real. I 
had only obtained a momentary glimpse when the sky 
became completely overcast, but fortunately the ensuing 
night was cloudless, and I was enabled to obtain another 
observation. The suspected object did not rise until soon 
after 1 a.m., and I knew that it would not come under the 
