on Mr, hutchins’s Experiments, 30; 
when in reality it was not, one of thefe thermometers in Head 
of having a vacuum above the quickfilver as ufual, was made 
' Vl ^h a bulb at top filled with air, in order that the preffure 
might ferve to force down the quicklilver. 
It the degree of cold at which mercury freezes had been 
known, a fpirit thermometer would have anfwered better; but 
that was the point to be determined. 
Another advantage which I expelled from the wooden ther- 
mometer was, that it would afford a guefs when a fufficicnt 
quantity of the quickfilver in the cylinder was frozen ; for if 
the cold was continued long enough to make that thermometer 
fink to near 400° below nothing, I fuppofed, a very vifible 
portion of the quickfilver would be frozen. 
It muff be obferved, however, that in Mr. iiutciiins’s ex- 
periments the natural cold approached fo near to the point of 
mercurial congelation, and in confequence the freezing mixture 
retained its cold fo long as to make thefe precautions of not fo 
much ute as they would otherwife have been. 
As it appeared, from Mr. Hutchins’s table of comparifon, 
that thefe thermometers did not agree well together, thev were 
all examined after they came back, except the ivory thermo- 
meter F, which was broke before it arrived. This lofs, how- 
ever, is of little confequence, as it appeared from the above- 
mentioned table, that F and G agreed well together. The 
boiling and freezing points were firfl examined in the prefence 
of Sir Joseph banks, Dr. blagden, Mr. hutchins, Mr. 
n airne, and myfelf, when the divifions on the fcale anfwering 
thereto were found to be as follows * 
