( 544 ) 
xPromifcum Experiments made in the Air-putnp likeiipife ^ hy the 
fame Perfons* 
WHen I began firft to keep Receivers void of Air, after the 
manner above-recited, I madeufeof Eels- skins to ^p- 
ply them clofe to the Cover. But I found them not proper 
forthings that are intended to be conferved ^ long time , becaufe 
by drying they grow fpringy , and this fpncg is capable to raifc 
the whole pillar of Air that prefles the Receiver againft its Co- 
ver^ %nd fo the Air gets in between, and fills the fpace ex- 
haufted. 
Afterwards I employed Mutton-skin 5 but that flicks yet lefs 
clofe than an Eel-skin : For, aflToon as the external Air comes to 
prefsuponit, it makes all the water, which wettech the skin that 
ftandsover without , enter into the emptied Receiver, and you 
may fee little drops of water coming out of the pores of the 
skin that is under the Receiver ; and after the water is all entred, 
the Air quickly gets in the fame way. 
At length I took a Lambskin , and by means thereof I have 
kept Receivers empty eight daies together , and never perceived 
it fail. Yet, for greater fecurity, I do put turpentine round a- 
bout fuch Receivers as I mean to keep ftaunch a long time. 
Mean while, this difference betwixt the skins of Mutton and 
Lambs is fomewhat remarkable, and confirms what Phyficians fay 
of the different CouftiDution of bodies in Youth and old Age. 
I have afterwards found , that Paper wetted fcrvcs as well as a 
Lambskin; but you muft put Turpentine about it before it be 
dry. 
One day I cover'd a Receiver, whofe fourth part was fill'd 
with water, and the reft all empty. I p^t it over the flame of a 
Candle, andfaw, that the water boiled very quickly, yet the 
glafs not much heated ; fo that the water boiled near a quarter of 
an hour with a great ebullition, andtheglafs was no more than 
tepid. I then took it away from the flame , and faw, that the 
water continued a very great while boiling, and that it began 
again from time to time. I then believed, that the vapours, which 
had been raifed into the Air, were recondenfed by the cold, and 
that that made the hot water bubble up, as water ufually doth 
when 
