200 HYDRAULICS. 



end in the water, the other being supported on the 

 lower part of the winch I, by which the screw and 

 cylinder are turned round. As soon as the screw 

 is immersed in water, it immediately rises therein 

 by the orifice C, to the level of the surface of the 

 water E ; and if the point of the helix, or spiral, 

 which in the beginning of the motion is coincident 

 with the surface of the water, happen not to be on 

 the lower side of the cylinder, the water will, upon 

 the motion of the screw, move on in the helix, 

 until it come to the point which is on the under 

 side, and coincident with the w 7 atery surface : 

 wdien it is arrived at that point, which suppose at 

 O, it cannot afterwards possess any other part of 

 the spiral, than that which is upon the lowest part 

 of the cylinder ; for it cannot move from O to- 

 wards H, because H is situated higher; and since 

 this will ever be the case, after the surface of the 

 water in the helix has attained the point E, it is 

 plain, that it must always be on the under side of 

 the cylinder. But since the cylinder is in motion, 

 every part of the spiral-screw, from E to F, will by 

 degrees succeed to the under part of the cylinder: 

 the water, therefore, in the helix, must succeed to 

 every part thereof^ from E to F, as it comes on the 

 lower side ; that is, it must ascend on the low r er 

 part of the cylinder through all the length of the 

 pipe, until it come to the orifice at top, where it 

 will run out, as having nothing farther to sup- 

 port it. 



STEAM ENGINE. 



When w r ater is made to boil by being heated to 

 212°, it is converted into an elastic vapour, called 

 steam. This is familiarly known, by observing a 



15 



