320 APPENDIX. 
oncd in Expcvimcnt LXXVII. Vol. I. p. ipi. 
I found that with equal Weights they were 
comprefled exaftly in the fame Proportion 
with common Air, which was included with 
them in the Condenfer. I tried alfo Air 
which had been difUlled from Pvhenifli Tartar, 
the Day before, which I repeated again a 
Week after, in which time one fourth of the 
Air of Tartar had lofl: its Elaftieity, as I 
found by the Degree of rifing of the Water 
up the inverted Tube, in which it was con- 
tained. That I might with the greater Cer- 
tainty be allured of the Degrees of Compref- 
fibility of thefe different Airs, 1 divided the 
Capacities of two equal Tubes into quarter 
cubic Inches, by pouring feverally thofe 
Quantities of Water into the Tubes, and 
then cutting Notches with a File, on the 
fides of the Tubes at the feveral Surfaces of 
the Water ; by which means I could fee by the. 
afeentof the compreffed Water in the Tubes, 
chat both the faftitious and common Air 
were exadly alike comprcfTible in all Degrees 
of Compreffure, from the beginning till they 
were loaded with a Weight equal to that of 
three Atmofpheres, which was the fartheft 
that I durfl venture, for fear of burfting the 
Glafs Receiver. 5)4. And 
