29'3 On the Principles of Pump-JFork, 



sel, there will be nothlnsi; to sustain the column «FE? of 

 the liuid over it, which therefore must descend through it 

 by its weight. 



1,7. The particles on the surface contiguous to the de- 

 scending column at ff and b will lose their lateral support, 

 and nmst therefore fall in and descend ; and as this will be 

 the case of all the particles in the surface, the whole surface 

 will also descend. 



16. By this means there will be supplied a constant de- 

 scending colunni of the fluid thn)ngh the hole till all is run 



• out. 



17. If the hole were made in the side of the vessel at D, 

 the fluid woidd issue out by the same Ititeral force, and with 

 the same velocity. , 



18. If the descending column be received into a recurved 

 hollow tube or pipe FNGlll, of any form or size, it will 

 rise in that pipe to the same horizontal level with that in 

 the reservoir AD, viz. to the line AH, and no higher. 



19. The air being taken out of the tube NIT I, will cause 

 the water to descend in the reservoir from AB to KL, by 

 the pressure of the air AXYB over it, and at the same 

 time it will rise from H to I in the tube. 



-20. Since the water in ABKL is equal to that in the 

 tube froni H to I, the velocity of that in the reservoir is to 

 the velocity of that in the tube as AK ta III, or as the 

 square of the diarteter of the tube to the square of the dia-.- 

 meter of the reservoir. 



Pig. 2. 



21. If AB be a surface of water, in which a till tube or 

 pipe BE i? placed, and open at the end B ; then if the ait- 

 be extracted front'this tube at the vipper end E, the water 

 will rise therein to the height BD by the pressure of the 

 column of air AX, upon an equal base. 



2^. The weight of the colunm of water BD will be pre- 

 cisely equal to the weight of the column of air on the same 

 base A or By ati^' extending -to the height of the atniq- 

 .sphere. 



Pig. 0. 



23. It is found by experience, that when the air is of a 

 -mean gravity it. wijl sustfiii ;i column of mercury in the 

 tube AB of a bdrojiietef/t^dtligr height C, equal to C9./ 

 inches. ' ' ^'' 



24. It is also known that mercury is about 14 times 

 heavier than watery therefore the pressure of the air in such 



a ease 



