428 SUPPLEMENT. 



from falling, and keep it in an 

 upright position : And then the 

 piece EFG is to be put on, the 

 part G sliding tight into the dove- 

 tailed groove H to keep the weights 

 NN horizontal, and the wire M 

 upright ; there being a round hole e in the part E F for 

 receiving the wire. 



There are four upright pins in the four corners of the 

 box within, each almost an inch long, for the board L to 

 rest upon ; to keep it from pressing the sides of the 

 bladder below it close together at first. 



The whole machine being thus put together, pour 

 water into the tube at top ; and the water will run down 

 the tube into the bladder below the board ; and after the 

 bladder has been filled up to the board, continue pour- 

 ing water into the tube, and the upward pressure which 

 it will excite in the bladder, will raise the board with 

 all the weight upon it, even though the bore of the tube 

 should be so small, that less than an ounce of water 

 would fill it. 



This machine acts upon the same principle, as the 

 one last described, concerning the Hydrostatical Para- 

 dox. For, the upward pressure against every part of 

 the board (which the bladder touches) equal in area to 

 the area of the bore of the tube, will be pressed upward 

 with a force equal to the weight of the water in the 

 tube ; and the sum of all these pressures, against so 

 many areas of the board, will be sufficient to raise it 

 with all the weights upon it. 



In my opinion, nothing can exceed this simple 

 machine, in making the upward pressure of fluids evi- 

 dent to sight. 110 



Note ISO. The application of this principle in hydrostatics to the 

 construction of a very useful and powerful press, is well worth atten- 



