{ t3 
upon them, a 'Thermometer applied to boiling Wa- 
ter might, at Sea, where the Motion of the Ship 
hinders Observations with the Barometer, ferve to 
determine the Difference of the - Gravity of the At r 
mofphere. See his Ch£fpi$ry 9 Tom. 1 . p. 171. 
Thefe, and ail other Liquids, by a certain deter- 
minate Degree of Cold peculiar to each fort, lofe their 
Fluidity, and freeze, or become, folid, but not in the 
fame Order as by Heat they boil 5 for by Cold Oil or 
Water is fooner frozen than Spirit of Wine, tho* Spirit 
of Wine will boil foonerthan Oil or Water. Ailfolid 
Bodies likewife, as Minerals, Metals, and even Stones* 
will become fluid, or melt, at a certain Degree of 
Heat peculiar to each Species,- and, when thoroughly 
melted, it is probable they are capable of receiving 
no higher Degree of Heat, 5 and, on the Abfence of 
that Heat to a certain Degree, they all return to 
their natural folid State. Hence we may reafonably 
conclude, that Solidity is the natural State of ail Bo- 
dies ; and that fome are only accidentally fluid, be- 
caufe their Conftitution is fuch as to melt by thofe 
Degrees of Heat which our Atmofphere is moft com- 
monly fubjed to. All folid Bodies are obferved to 
contrad themfelves into fmaller Dimenfiom by Cold, 
and gradually to expand themfelves at the Approach 
of Heat, till at laft, being by Heat forc'd to the greateft 
Degree of Expanfion, the Particles of which they are 
compofed lofing their Cohefion, they become fluid j 
but no Experiments have yet been made, which de- 
termine whether Solids, expofed to Cold beyond 
certain Degrees, will ceafe to contrad any more. 
The learned Dr. Mufchenbroek , Prof, of Aftronomy 
at Utrecht 7 and F. R . S . hath lately invented a very 
ingenious 
