( 6 S o ) 
V. An Account of feveral Experiments tnadetoex- 
amine the Nature of the Expanfion and Con- 
1 raSiion of Fluids by Heat and Cold, in order 
to afcertainthe Divifions of the Thermome- 
ter, and to make that Injirument, in all places, 
without adjujiing by a Standard. By Mr. Edm. 
Halley, S. R. S. 
OZJalities, fuch as Heat and Cold, Moifture and 
Dricefs, and the like, are nototherwife to be efti- 
maccd, but by their EfTed: on the Quantity of (bme body j 
they adi on, encreafing or lefTening the Dimenfions there- 
of or elfe by the Motions- they produce, both which ; 
fubjedt them to Menfuration ; but it is (till a Queftion | 
how to afcertain the proportional Heat or Cold, &c; 
that is between any two Climates or Seafons, fo as to \ 
conclude the one, tor Example, twice as hot or twice as \ 
cold as the ether, tho' the Inftruments now in u(e abun- j 
dandy fuffice to (hew when the Temper of the Air is j 
the lame, and when it is Warmer or Cooler. The : 
Reafon hereof is, that we know not the Caules of the j 
Expanfion of Fluids by Heat, or of their Contraction 
by Cold, as arifing from the Nature of their condiment 
parts, which are (6 far from being Obje&s of our Sence, 
that they even furpafs our moft refined Reafonings, and 
extort a Confeffion of our Ignorance after all our En- i 
deavours. For the fame degree of Heat does not pro-.ll 
portionally expand all Fluids ; ibme (Veiling with a gen-jj 
tie Warmth, and others not till they be confiderably i 
Hot ; fome boiling with a moderate Heat, and others not i 
at all. Some capable of great Expanfion, others en- 
creafing very little ; fo that it may well be concluded j 
that no one of them does encreafe and diminilh in tht | 
(amc 
