Si - Mr. PRINCE’S Account of 
range, to a place referved the whole height} to get at the under. 
‘part of the gegisrgloc, and fix apparatus to it for fome ex- 
periments. | In this place ftand the Jong tubes, and fuch- tall 
glafles, belonging to- the. apparatus, as will not go into the 
drawers. "The barrels, &c. of the pump are:covered with. a 
«cafe; or head, which keeps:them from duft and accident, when 
the pump isnot. in.ufc. «Ihe apparatus is: fecured between fli 
-ders,; &c.. in the. drawers, fo that the whole machine —_ "be 
e removed, in one body, ~vithout:danger. o ~ 
Having given you this account of the machine, T. — Sir, 
I could add to: at, at this time, the refult by experiment, and 
inform. you.to: what degree it will-rarefy the air; but the want 
pu a pc Dodo to meafure the rarefaction, "prevents me. 
-; As we have no glafs-manufactory here, I fent. to Europe for 
-my apparatus, about twelve months (ince : but, unluckily, this 
: -part,. with fome ‘others, have not yet been forwarded to me. 
AS fon 3 as I-ean fatisfy myfelf, I will let you know the refult. 
L have, a at. prefent, only a {mall tube. -of two-tenths-inch. bore, I 
accidentally met ey which I ufe as a common gage : — 
this will.not:determine the power of the pump. — — 
~All I can à of the inftrument at prefent is, that T find it 
iud more convenient to ufe than one of the common fort : 
-that it-will exhauft a receiver much fooner, and keep in order 
„much longer, for being made without valves, which muft de- 
pend on the {pring of'theair to open them. When a common 
pump, which I have, has been fitted up with valves, leathers, 
Jc. at "the fame time with this ; the valves of the common 
pump have become too dry and fig to ufe, while this pump 
i “has: ‘continued i in good order. I attribute this, in part, to the 
moifture which the valves on the PUN: receive from the 
eee ers . piftons 
