[ 6 7 7 ] 
ingenious Ihftrument, which he calls ’a ^Pyrometer 
and which Dr. ‘Defaguliers hath made fome Im- 
provements to *'5 a full Defcription of which he 
hath given in his Courfe of Experimental \ Philofo J 
fhy, Vol L J?. 421. &c. By this Inftrument the 
Elongation of Rods of feveral Sorts of Metals by the 
Approach of a certain Number of Flames of a Spi- 
rit-Lamp, and likewife their as fudden Contradion, 
on the extinguifhing one or more of thofe Flames, 
is render'd fenfible to the Eye: Which fufficiently 
evidences the Matter of Fad, and puts it beyond all 
Doubt. 
From the above-mention'd Property of Bodies 
contrading and expanding in Cold and Heat, have 
all Thermometers been conftruded, that have ever 
been made ufe of in order to obferve and compare 
the different Degrees of Heat, either in our Atmo- 
fphere, or in other Bodies. The moft fimple and 
moft fenfible of any is that aereal Thermometer de- 
feribed by the great Mr. Boyle, in his New Experi- 
ments and Obfervations touching Cold, Land . 2683. 
4 to. p. 39* It confifts of a glafs Bubble, with a 
very Bender Stem not bigger than a Raven's Quill. 
The Bubble is left full of Air, and a few Drops of. 
Water being convey'd into the Stem in an ered 
Pofition, will there remain fufpended to a certain 
Height; but, by the leaft Addition of Heat, the Air 
in the Bubble expanding will pufh the Water up 
higher 
* This Inftrument hath fince been greatly improved by that ingenious 
Watch-maker Mr. John Rllicot ? F. R, S. See Phil. Franf. N°, 443. 
