252 Mtfcellanea Curiofa* 



tlon and Contraction, efpecially with a mode- 

 rate degree of either Heat or Cold. Now this 

 being allow'd as a Standard, and the other 

 Thermometer that includes Air, being gradua- 

 ted with the fame Divisions, fo as at the time 

 when the Air was included, to agree with the 

 Spirit- Thermometer in all the degrees of Heat and 

 Cold, noting at the fame time the precife height 

 of the Mercury in the common Barometers : 

 It will readily be underftood, that whenlbever 

 thefe two Thermometers fhall agree, the pref- 

 fure of the Air is the fame it was, when the 

 Air was included, and the Inftrument gradua- 

 ted : That if in the ^it-Thermometer the Li- 

 quor ftand higher than the Divifion marked 

 thereon, correlponding with that on the Spi- 

 rit»glafs, it is an indication that there is a 

 greater preffure of the Air at that time, than 

 when the Inftrument was graduated. And the 

 contrary is to be concluded, when the Air-glafi 

 ftands lower than the Spirit, vi%. that then the 

 Air is fo much lighter, and the Quick filver, in 

 the ordinary Barometer lower than at the faid 

 time of Graduation. 



And the Spaces anfwering to an Inch of Mer- 

 cury, will be more or left* according to the 

 quantity of Air fo included, and the fmallnefs 

 of the Glafs Cane, in which the Liquor rifes 

 and falls, and may be augmented almoft in a- 

 ny proportion, under that of the Specifick Gra- 

 vity of the Liquor of the Thermometer to Mer- 

 cury. So as to have a Foot or more for an 

 Inch of Mercury 9 which is another great con- 

 venience. 



