[ 6 9 ° ] . 
be adapted to meafure flill greater Degrees of Heat, 
till the Materials themfelves melt into Glafs. 
I fhould advife, that not only the Scale of this 
fort of Thermometer, but likewife of all others, be 
determined by Experiments, without regarding any 
Equality as to Meafure between the Divifions, and 
that in every Individual that {hall be made 5 for a 
Difference in the Length and Thicknefs of the 
Rods in this fort will make a Difference in the Scale, 
as much or more than the Inequality in the Cavity 
of the Stem, or glafs Tube of other Thermometers, 
which can never be juft, if applied to a Scale whofe 
Divifions are made equal ; unlefs the Cavity of the 
Stem be perfectly equal, which it is impoflible for 
any Workman to undertake to do, and which is very 
feidom, if ever, hit on by chance. Therefore, in 
thefe Inftruments, let the Point B in Fig. 3. or the 
horizontal Pofition of the Index, be the Situation of 
the Index when the Rod has ftood a Quarter of an 
Hour in boiling Water 5 there mark y- boiling on the 
outer Circle; on Fahrenheit's Arch mark 212. then 
let your xMachine up to the Mark -f- into melting 
Tin, which is the Metal that melts eafieft. When the 
Rod is arrived to its greateft Elongation in that Me- 
tal, inferibe the Chara&er % on the outer Circle ; 
do the like with Lead, and let the Charader ^ at it. 
At the boiling of Mercury put the Mark 5 , and on 
Fahrenheit's Arch jmark 600. the utmoft Extent his 
Mercurial Inftruments can meafure : Then proceed 
to the melting of Silver, and fet the Mark <[ ; at 
the melting of Gold place the Mark ® ; at the melt- 
ing of Copper place the Mark at the melting of 
Iron place the Mark <$, the moft difficult to melt of 
all Metals. 
As 
