1817.] reaching the North Pole from Spitzbergen. 387 
the most northerly parts of Spitzbergen that in the spring a great 
number of wild geese, ducks, and other birds, take their flight fur- 
ther north. 
32. Q.—What animals and birds have they during the summer, 
and what species winter on the island ? 
A.—In Spitzbergen they have wild rein-deer, white and blue 
foxes, and white bears, which remain continually on the island; but 
geese, ducks, &c. are only there in summer. 
33. O.—Those which quit Spitzbergen on the approach of winter, 
in what month do they generally emigrate, and to what point of the 
compass ? 
A.—All the before-mentioned birds on the approach of winter, 
that is, in the latter end of September, fly to the southward, and 
return again in the latter end of April. 
N.B. The 31st and 33d answers do not apparently agree. 
ARTICLE IX. 
On the Temperature at which Water is of the greatest Density. 
By George Oswald Sym, M. A. 
Ir might be thought a very simple problem to determine at what 
‘temperature a given quantity of water occupies the smallest space ; 
yet, though a greater share of attention and ingenuity has been be- 
stowed upon this subject than its importance may seem to merit, no 
certainty with regard to it has hitherto been attained. Most chemists 
believe the greatest density of water to be at or near 40° ; but some 
of very high authority place it at 36°; and there are probably not,a 
few who still indulge a philosophical reluctance to admit that the 
condensation can be any where greater than at the freezing point. 
The question is, therefore, still undecided, and continues to afford 
a proof how difficult it is to establish a fact of which no good..ex- 
planation can be given. 
In addition to the various methods which have been contrived for 
settling this point, I venture to propose another, depending on the 
-eonstruction of an instrument, which seems adapted for directly 
measuring the real expansions and contractions of fluids, 
In order to construct this instrument, two glass tubes are to be 
procured, equal to each other in length, and equal in weight; but 
so unequal in width, that the one may slide easily into the bore of 
the other, and leave a sensible space unoccupied all around. A 
certain portion at the end of the larger of these tubes is to, be 
melted, and blown intoa bulb. An equal portion at the end of the 
smaller is.also to be melted, and so pushed back and compressed 
that the whole length of the two may still remain equal, and that 
2B2 
