PA YEBNirS HYDROSTAT. 277 



When they wish to rise again to the surface, the 

 men re-enter the between -decks by the shaft, which 

 they close hermetically. The pump is worked so as 

 to withdraw the air from the hold, and transmit 

 it to the orlop-deck and gallery. The water escapes 

 by the pi[)e communicating with the exterior. The 

 hydrostat becomes lighter as the hold fills with 

 water, and soon floats on the surface as before. The 

 men then open tlie hatch, and obtain communication 

 with vhe outer world. The hydrostat is removed 

 from one s[)ot to another by towing. 



The hold is square. It measures about 26 feet in 

 the side, by 6 feet 6 inches in depth. The orlop-deck 

 has the same dimensions. Tiie heiween-decks has the 

 same depth, but measures only 16 feet in the side. 

 The hydrostat is, tlierefore, nearly 20 feet in height, 

 and its base, which has the bottom of the sea for a 

 floor, covers an area of 625 square feet. We have 

 already stated that an airtight gallery surrounds both 

 the lower storeys. This gallery, like the orlop-deck, 

 is divided into a number of smaller compartments, 

 which can be made to communicate, or kept distinct, 

 by means of stopcocks. 



M. Payerne's submarine hydrostat resolves several 

 difficulties at once. By interior arrangements, as we 

 have seen, it may be made to rise or fall at will, and 

 it will readily float about like a raft. This ingenious 



