42 WONDERS OF THE DEEP 



and the bottom being strong enough to resist the 

 pressure of the water of the ocean. 



At its lower end the tube expands into a 

 spherical observation chamber five feet in diameter, 

 one side of which is provided with a large funnel- 

 shaped window. This observation chamber is made 

 of; cast-iron and weighs four tons. In submarine 

 photographic work two persons usually occupy this 

 observation chamber at the same time, one to take 

 the pictures through the heavy glass window, the 

 other to act as look-out and to give orders to the 

 deck crew overhead. A simple ventilating device 

 freshens the air, so that one may remain below 

 for an indefinite period quite comfortably. 



The raising and lowering of the observation 

 chamber is controlled by two chains that are attached 

 to the chamber, and run to chain hoists on the deck, 

 which alter the position of the chamber according to 

 the instructions of the observer below. As the tube 

 is lengthened for deeper and deeper lowering into the 

 ocean, its bottom folds are more and more squeezed 

 together under the increasing water pressure, until, 

 at considerable depths, a section of the tube, that 

 would be eleven feet long when fully extended and 

 would weigh a ton, is compressed into about three feet 

 and still weighs a ton. In other words, through this 

 contraction a given length of tube becomes heavier as 

 it sinks deeper, and this automatic adjustment ensures 

 the proper balancing of the tube in the sea. 



The apparatus used by the Williamson Submarine 

 Expedition may appear rather simple in construction, 



