PROTO-BATHYSPHERES 53 



for respiration above one quarter of an hour; the breath 

 which is often sucked in and out, being so corrupted by 

 the mixture of vapours, that Nature rejects it as unserv- 

 iceable. Now in an hour a man will need at least 360 

 respirations, betwixt every one of which there shall be 

 10 second minutes, and consequently a great change and 

 supply of air will be necessary for many persons, and any 

 long space. 



"And so likewise for the keeping of fire; a close Vessel 

 containing ten cubical feet of air, will not suffer a wax 

 candle of an ounce to burn in it above an hour before it 

 be suffocated, though this proportion (saith Mersennus) 

 doth not equally increase for several lights, because four 

 flames of an equal magnitude will be kept alive the space 

 of 16 second minutes, though one of these flames alone 

 in the same Vessel will not last above 25, or at most 30 

 seconds, which may be easily tried in large glass bottles, 

 having wax candles lighted in them and with their mouth 

 inverted in water. 



"For the resolution of this difficulty, though I will not 

 say that a man may by custome (which in other things 

 doth produce such strange incredible effects) be inabled 

 to live in the open water as the fishes do, the inspiration 

 and expiration of water serving instead of air, this being 

 usual with many fishes that have lungs; yet it is certain 

 that long use and custome may strengthen men against 

 many such inconveniences of this kind, which, to unex- 

 perienced persons may prove very hazardous: and so it 



