OF HYDRAULICS. 



127 



The foun- 

 tain at 

 command. 



scend in the longer leg C B G, and run through the LE cr. 

 bottom, until the cup be emptied. 



This is generally called Tantalus's cup, and the legs 

 of the syphon in it are almost close together ; and a 

 little hollow statue, or figure of a man, is sometimes 

 put over the syphon to conceal it ; the bend E being 

 within the neck of the figure as high as the chin. So 

 that poor Tantalas stands up to the chin in water, ima- 

 gining it will rise a little higher, and he may drink ; 

 but instead of that, when the water comes up to his 

 chin, it immediately begins to descend, and so, as he 

 cannot stoop to follow it, he is left as much pained 

 with thirst as ever. 



The device called the fountain 

 at command acts upon the same 

 principle with the syphon in the 

 cup. Let two vessels A and B 

 be joined together by the pipe C 

 which opens into them both. Let 

 A be open at top, B close both 

 top and bottom (save only a small 

 hole at b to let the air get out 

 of the vessel B, and A be of 

 such a size, as to hold about six 

 times as much water as B. Let 



a syphon D F be soldered to the vessel D, so that 

 the part D E e may be within the vessel, and F with- 

 out it ; the end D almost touching the bottom of the 

 vessel, and the end F below the level of D : the vessel 

 B hanging to A by the pipe C (soldered into both) and 

 the whole supported by the pillars G and H upon the 

 stand /. The bore of the pipe must be considerably 

 less than the bore of the syphon. 



The whole being thus constructed, let the vessel A. be 

 tilled with water, which will run through the pipe C, and 

 fill the vessel B. When B is filled above the top of 

 the syphon at E, the water will run through the syphon, 



