( 493 ) 
ihe Pores or Tnterflices of a Spunge) and how much that 
little will be contracted by the Preffure of the in- 
cumbent Water, it cannot be believed that a Supply, by 
this means obtained, can long fubfift a Diver. Since by 
Experiment it is found that a Gallon of Air, included in 
a Bladder, and by a Pipe reciprocally infpired and expi- 
red by the Lungs of a Man, will become unfit for any 
further Refpiration, in little more than one Minute of 
Time ’■> and though its Elafticity be but little altered, yet in 
palling the Lungs , it lofes its vivifying Spirit , and is 
rendred effete, not unlike the Medium found in Damps , 
which is prefent Death to thofe that breath it ; and which 
in an inftant extinguilhes the brighteffc Flame, or the 
fhining of glowing Goals or red hot Iron, if put into it. 
I fhall not go about to fhew what it is the Air lofes by 
being taken into the Lungs , or what it communicates to 
the Blood by the extream ramifications of the Afpera Arte- 
ria , Co intimately interwoven with the Capillary Blood - 
Veffelsi much lefs to explain how ’tis performed, fince 
no difeovery has yet been made, to prove that the ulti- 
mate Branches of th zVeins and Arteries there, have ariy 
Anafiomofes with thofe of the Trachaa ,* as by the Micros- 
cope they are found to have with one another. But I ra- 
ther choofe to leave this Enquiry to the Curious Anato- 
mijl, to whom the Stru&ure of the Lungs is better under- 
ftood ; and fhall only conclude from the aforefaid Ex* 
periment, that a naked Diver, without a Spunge , may 
not be above a couple of Minutes enclofed in Water, (as 
I once faw a Florida-Indian at Bermudas ) nor much longer 
with a Spunge, without Suffocating ; and not near fo long 
without great Ufe and Pra&ice .• ordinary Perfbns gene- 
rally beginning to flifle in about half a Minute of Time. 
Befides if the Depth be confiderable, the preflure of the 
Water on the V effels is found by Experience to make 
Gggg the 
