100 REPORT—1840. 
186. M. Kupfier*, though he adopts Kamtz’s table of elastici- 
ties, after examining the experiments of Gay-Lussac, Bohnen- 
berger, Auguste, and Erman, finally prefers this value of m, 
1h Vt i ae a eG Hi 8 2 
almost coincident with that of Bohnenberger and Apjohn. 
187. A most elaborate paper has been published by Mr. Prin- 
sep, of Calcutta, in the Journal of the Asiatic Society of Bengal7, 
on the wet-bulb problem, in continuation of the ingenious, but 
rather obscure ones, alluded to in the former report, as having 
been published in the ‘* Gleanings of Science’’t. Mr. Prinsep 
states, that the notice taken of his former labours, in the First 
Report of the British Association, had stimulated him to re- 
sume the subject, and he has accordingly furnished us with a 
great many valuable test-experiments, which can nowhere be 
so well performed as in warm climates. Mr. Prinsep’s ori- 
ginal memoir will be consulted by those who wish to avail 
themselves of his valuable researches for the improvement of 
theory : it is not necessary to dwell upon those points where he 
seems to us to be less explicit, or historically not quite exact ; 
and the great point is to be clearly satisfied that we have now-ub- 
tained a sufficient interpretation of the indications of the moist- 
ened thermometer. When we find that Mr. Prinsep once more 
coincides with Dr. Apjohn’s numbers, only hesitating whether 
to prefer j; to ,', for the value of m, we are prepared to admit 
that this problem is, practically speaking, completely resolved ; 
and this being the case, it is scarcely worth while to disentangle 
the various imperfect steps by which so happy a consummation 
has been attained, and the hygrometer rendered as commodious 
and as accurate as the common thermometer§. The leading 
steps of the generalization are these :—Hutton invented the 
method; Leslie revived and extended it, giving probably the 
earliest, though an imperfect theory; Gay-Lussac, by his ex- 
cellent experiments and reasoning from them, completed the 
theory, so far as perfectly dry air is concerned; Ivory ex- 
* Bulletin de ’ Académie des Sciences de St. Petersbourg, vi. No. 22, for 
which I ani indebted to Major Sabine. 
+ No. 55, July, 1836. 
t The “ Gleanings in Science’”’ referred to in the original Report of the 
British Association, had been lent to me by Sir D. Brewster, to whom they had 
been sent. I afterwards communicated them to Dr. Apjohn. 
§ In practice, I am inclined to prefer two separate thermometers to the dif- 
ferential one of Leslie, which requires besides, the use of a common thermo- 
meter, to take the temperature of the air. It seems preferable to have two 
thermometers arranged in one pocket-case, and in the event of fracture a single 
one may still be used. I have formerly adverted to the unnecessary introduc- 
tion of the term psychrometer to express so simple a combination. 
