f 495 ) 
of a TruUate Cvlts the- (mailer Baft* befog ilofed*‘awd 
the larger open; and ©tight to be fo pb'iied with Lud, 
and fofufpended, that the Veflel ifiay ffoik foil of Air, 
with its greater or open Bajis downwards, and as near 
as may be in a fituation parallel to the Horizon, fo as to 
clofe with the Surface of the Water .all at once/ Uhder 
this Cotivercle the Diver fetting^ finks down together 
with the included Air into the Depth defired ; and if the 
Cavity of the Veflel may cohtatn a Tun of Vffyttr, a 
Angle Man may remain therein at lead an Hour, without 
much inconvenience, at five or fix Fathoms Deep; But 
this included Air, as it defcends lower; does ebhtrifcff it 
felf according to the weight of the Water that comprefles 
it ; fo as at thirty three Foot deep or thereabouts, the 
Bell will be half full of Water, the Preflure of it being 
then equal to. that of the whole Atmofphere and at all 
other Depths, the fpace occupied by the compreft Air in 
the upper part of the Bell ; will be to the under part of its 
Capacity fill’d with Water, as thirty three Feet to the 
depth of the Surface of the Water in the Bell below the 
common Surface thereof. And this condenfed Air, being 
taken in with the Breath, foon infinuates itfelf into all 
the Cavities of the Body, and has no fenfible effect, if 
the Bell be permitted to defoend fo flowly as to allow 
time for that purpofe. The only inconvenience that at- 
tends it, is found in the Ears, within which there are Cavi- 
ties opening only outwards, and that by Pores fo fmall 
as not to give admiflion even to the Air itfelf, unlefs they 
be dilated and diftended by a confiderable Force. Hence 
on the firft defeent of the Bell, a Preflure begins to be felt 
on each Ear, which by degrees grows painful, like as if 
a Quill were forcibly thruft into the Hole of the Ear; 
till at length, the force overcoming the Obftacle, that 
which conftringesihefe Pores yields to the Preflure, and 
letting fome condenfed Air flip in, prefent Eate enfues. 
Gggg i Buc 
