FREEZING AND FORCE. 



is filled quite full with water. A small disc of 

 thin copper sheet, C, is dropped into a recess 

 turned out of the upper end of the cylinder, 

 and so held central. Over the disc is placed a 

 strong ring- washer, D, of brass or gun-metal, 

 to transmit pressure from the hexagon nut, E, 

 which screws on to the cylinder. The hexagon 

 nut has a hole drilled through it corresponding 

 to that in the ring-washer, so that the middle 

 of the outer surface of the copper disc is visible 

 through ring-washer and nut. 



Fl<5. 32.-BURSTING FORCE OF WATER FROZEN IN CONFINED 

 SPACE. 



By screwing up the nut, the disc can be 

 squeezed very hard between the cylinder and 

 ring-washer, so that the chamber in the cylinder 

 is hermetically sealed. 



When the chamber is thus closed, full of 

 water, without a bubble of air, the whole is 

 placed in a freezing mixture such as that already 

 described (two parts of pounded ice or snow 

 to one of salt), which nearly covers it, leav- 

 ing just the open end of the nut visible. 



The cylinder, with the water inside, is soon 

 cooled down to freezing-point, and below it. 



'35 



