;j 4-3 Dr. blagden’s Dlftory of 
The old fpirit- thermometer called H was erroneous no lefs 
than 7 0 or 8° near the freezing point of water, which ferved 
as a kind of compenfation in the lower parts of the fcale, fo as 
to make it agree tolerably well with thofe of mercury in the 
greatef cold of the frigorific mixtures. 
Although in two of Mr. Hutchins’s thermometers the 
quickflver funk exceedingly low, to — 450° or near - 500°, 
there is reafon to believe he did not in any inftance obtain the 
extreme term of contradlion, fince Profefior braun, in fome 
of his lafl experiments, brought the mercury in one thermo- 
meter to - 544 0 , and in another to -556 0 *. Hence it would 
feem, that Mr. hutchins had always fome part of the quick- 
fiver left unfrozen, or fome vacuity remaining, either ill the 
fern or the ball of his inf ruments ; and as no objection appears 
againf thofe experiments of M. braun’s, we muf conclude, 
that quickflver, in becoming folid, contracts about a 23d of 
its whole bulk. When the principal objedt in view is to deter- 
mine the quantity of this contraction-, it will be moft expe- 
dient to perform the experiment in the leaf degree of cold 
which will permit the quickflver to be entirely frozen, that it 
may not be fo likely to flick, faff in the tube ; but care mufl be 
taken to congeal the whole of the mercury in the flem as well 
as that in the bulb. 
Among the numerous improvements in natural knowledge 
which have been made within a fhort period of years, perhaps 
none tends to illuflrate more phenomena of nature than the 
late difeovery, that a confiderable quantity of heat difappears 
when bodies pafs into a fate of fluidity or elaf ic vapour, and 
re* appears when they are converted back again to their original 
condition. This remarkable effedl of fuch changes, I believe, 
* Nov. Comment. Fetrop. tom. XI. p. .31.3, 
7 
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