204 Proceedings of the Royal Irish Academy o 
attacked were treated, twelve of the cases proyed fatal. Each of these, 
witliont exception I belieye, was made the subject of careful inquest 
by the coroner, aided by an autopsy conducted usually by some of our 
most skilful surgeons and physicians. "Whilst the exciting cause in all 
these cases was doubtless the exposure of the system to the pressure 
of the condensed air of the chamber, the habits and condition of several 
of those who died were, at the time they went to work, such as would 
have excluded them from it if subjected to the examination of Dr. Ja- 
minet ; and the verdict in about one-half of the cases gave a totally 
different cause for the death of the patient, i^early or quite all of 
these deaths happened to men unaccustomed to the work ; several of 
them to men who had worked but one watch of two hours. In con- 
trast to this is the fact that quite a large number of the men (cer- 
tainly one-half of those constantly employed) commenced with the 
work at its inception, and remained throughout its continuance entirely 
without injury or inconvenience. 
* * Much diversity of opinion was expressed by the medical gentle- 
men who investigated the symptoms, and held autopsies of the deceased. 
Some of these gentlemen maintained that a slower transition from the 
abnormal to natural pressure would have been less injurious ; others 
claimed, on the contrary, that it was from the too rapid application of 
pressure in passing from the natural into the compressed air. The fact 
that the air-lock tenders were in no case affected, although subjected 
many times during a watch of two hours in the air-lock to rapidly 
alternating conditions of the atmosphere, at one moment in its normal 
state in the lock, and five minutes later exerting a pressure of 50 lbs. 
per square inch upon every part of the body, would seem to prove both 
of these theories unsound, and lead us to believe that in the length of 
time to which the human system is subjected to this extraordinary 
pressure exists the real source of danger, and not from any rapid alter- 
nations of pressure to which it is exposed. After the caisson reached 
the rock, I have frequently, when passing through the air-lock, ad- 
mitted the compressed air into it so quickly that none but those well 
accustomed to it could relieve the pressure upon the.'r ears, and yet I felt 
no ill effects whatever from this rapidly increasing pressure ; and in 
going out I have let the pressure off so fast that the temperature in the 
lock has fallen thirty-two degrees, Fahrenheit, in consequence. These 
transitions occupied but three or four minutes. 
' ' The fact that the air-chamber was briefly visited by thousands 
of persons, including many delicate ladies, even after it had reached 
the bed-rock, some remaining as long as an hour in it, without any of 
them experiencing the slightest ill effects from the pressure ; and the 
fact that no cases of any importance whatever occurred among the 
workmen after the watches were reduced to one hour, satisfies me 
that this is the true cause of the paralysis, and that by lessening still 
more the duration of the watches, a depth considerably greater can be 
reached without injury to the workmen. Too long a continuance in 
the air-chamber was almost invariably followed by symptoms of ex- 
haustion and paralysis. 
