Chap. 2.] of each oiler as to Weight cr Preffure. 405 



with a cylindrical ferule of copper of an inch diameter 

 D, which is to be flopped with a pifton G, or the 

 fucker of a pump well fitted to the ferule, and oiled, 

 that it may yield to a moderate preffure. Let the 

 piiton be fupported by a fmall rod G H, fattened at 

 H to the filk which unites with the portion of the 

 pulley M, with which the extremity of the lever M N 

 is furnifhed, and which has for its center cf motion the 

 point L. The other portion of the pulley N, which 

 terminates the other extremity of the lever, is alfo fur- 

 nifhed with lines of filk, which fupport the fmall bafon 

 or fcale T. Upon the copper ferule D then fit a cy- 

 lindrical tube of glafs F K, the interior diameter of 

 which is equal to that of the ferule, and its height 

 equal to that of the vefiel A B. When the apparatus 

 is difpofed in this manner, fill the tube E F with water, 

 and conrnue to put fmall weights into the bafon or 

 fcale I, until the pifton begins to rife. Afterwards 

 take away the glafs tube E F, and place the pifton G 

 in the copper ferule D, and pour water into the large 

 veflel A B, and it will appear that the fame weights as 

 before in the bafon I, will raife up the pifton when 

 the larger vefTel A B is entirely full,. Hence it fol- 

 lows that there is the fame power to be counteracted, 

 whether there refts upon the pifton only a column 

 of water of its own fize, or whether the ye/Tel A J3 is 

 entirely Tull. Such a column, therefore, prefles upon 

 its bafe independently of the reft of the water con- 

 tained in the veflel. 



To account for this, let us fuppofe all the water in 

 a veffel to be divided into feveral columns, i, 2, j, 

 4, 5, (plate V. fig. 2.) each comppfed of an equal 

 number of parts. If the bottom of the veffel, which 

 ferves for the bafe and fupport of all the columns, is 

 opened in a, the column 3, being no longer fupported, 

 P d 3 will 



