112 WHITNEY: 



smoking in high pressure, flames often spurting from a cigar 

 or pipe, which is consumed with great rapidity. Fire in a 

 caisson or tunnel heading where there is timbering, is a very 

 serious accident, as if once started it is almost impossible to 

 extinguish it. 



The acoustic effect is to deaden sound, the waves not 

 vibrating freely in highly compressed air. This effect begins 

 to be noticeable at about two and a half atmospheres. 



In survey work, involving sighting from normal into 

 compressed air, or from one pressure into another, through 

 the plate glass portholes of the locks, a marked degree of 

 refraction is experienced. 



Among other phenomena, is the very rapid growth of 

 fungi, and other forms of vegetable life, upon wood, or on 

 wet mud. It is probable that a crop of mushrooms could be 

 raised with great rapidity under three or four atmospheres. 



Rats from time to time get into the empty qars sent from 

 the surface of the earth and are shot through the car-locks 

 with great rapidity. In the tunnels they breed and so long as 

 they can get food from -portions of dinners left by the workers, 

 they seem as active as upon the surface. After living a few 

 weeks or months in the pressure, they are found to die, when 

 the "air" is lowered to normal pressure. Formerly mules 

 were worked in caissons and tunnels under "air," but the 

 more economical application of electric and pneumatic power 

 has superseded them. On removing animals from a pressure 

 in which they had lived for da3'S or weeks, it was customary 

 to take from 12 to 24 hours to bring them out, and to give 

 them oats soaked in whiskey, before entering the lock. 



The human eye takes on a remarkable brilliancy in highly 

 compressed air, the pupil and iris suggesting the glitter of 

 polished metal. This may be due to conditions of circulation. 



As the intensity of pressure is increased, the worker's time 

 in it must be depreased. In extreme pressure, from fort3'-five 

 minutes to two hours at a time is as much as can be safely 

 allowed, with some hours of rest before again entering. 



