DIVING-BELLS. 383 



could be introduced, the diver within the bell would be as 

 effectively drowned as if there were no bell at all. 



The accompanying illustration is a kind of chart, so to speak, 

 of the mode in which air was formerly supplied to the bell. 



On the right hand is seen a section of the Diving-bell itself, 

 together with the seat on which the divers can rest. There is 

 also an escape-valve at the top of the bell, by which the vitiated 

 air can pass away ; but, as it is not essential to the subject in 

 hand, and is rather complicated in . structure, it has been 

 omitted. 



Immediately on the left of the bell is a cask, to which 

 several heaw weights are attached. This cask contained com- 



NEST OF WATEE- SPIDERS. DIVING-BELL. 



pressed air, and, after it was lowered by the side of the bell, 

 the end of the flexible tube was taken into the bell, the tap 

 turned, and the compressed air rushed into the bell, taking the 

 place of that which had been exhausted by respiration, and was 

 allowed to pass through the escape- valve. I may mention 

 that the divers unexpectedly discovered that, when they were 

 breathing compressed air, they could dispense with respiration 

 for a wonderfully long time, the amount of oxygen taken in at 

 a single breath being enough to renovate the blood more than 

 could be done by several ordinary inspirations. 



ON the left hand of the illustration is seen a sketch of the 

 nest of the now familiar Water-spider (Argyronetra aquatica], 

 taken from some specimens in my possession. 



