4^4 Q" ii( Utet-al Cummunlctitkn of Motlm in fluids, 



rive at the place of contradion which they aflunae at D F> fig. 5. and which they likewifd 

 aflume when the orifice is made in a thin plate. If we imagine a tube of glafs^K, one- 

 extremity of which is applied at K, fig. 6. and the other extremity open in the interior 

 part of the refervoir, it will be feen that the preflure of the atmofphere, which is exerted, 

 upon the coloured fluid T, muft likewife adl; on the furface of the refervoir, and join the 

 preflure of the fluid in the refervoir to prefs the watei; into the tube y K, as it prefles the 

 coloured liquor into" TS. The prefl'ure of the atmofphere muft, in the fame manner, 

 augment the impulfe of all the fluid particles which arrive at K L, and confequently mull 

 increafe the expenditure. 



Since the checks and eddies in an additional cylindrlc tube muft always deftroy a part 

 of the adlive force of the fluid, it follows, that the fluid column iflTuing out of the tube 

 tan never acquire the whole velocity which is due to the a£tual charge, and is obferved 

 . Hcarly entire in the orifices through a thin plate ; and the diminution of velocity correfponds 

 with the increafe of the time beyond, that ijodicated by the theory, a& may be fecn in the 

 following 



Evperlment XIX. The orifice P fig. i. being made through a thin plate, andthe vertical- 

 height P M, being 54 inches, the diftance M,N of the jet was 81,5 inches, fiaving 

 applied to the fame orifice the cylindrical tube of fig. 5. and the perpendicular P M being 

 let fall from the external orifice of the tube, the dUlance M N was found to be 69 inches. 

 According to the theory, the expenditure of four cubical feet through this tube ought to have 

 t^ken place in 26 '',24, but it really employed 31 ". And. the proportions 31'' : 26''^,24 =s 

 81,5 : 69 nearly. 



The fame obfervatlon may be made on an experiment of Michelotti (torn. ii. pages 2? 

 and 23]. P M being 19,33 f^^^j ^"i^ '^^ water ifluing through an orifice in a thin plate M N 

 was 23,2 feet •,, it was no more than 20 when an additional cylindric tube was applied 

 which had not even the proper length. 



It is evident, that the theory of the lateral communication of motion mufb likewife apply 

 in the fame manner to defcending and afcending tubes, whenever their form admits of thia 

 lateral communication. In defcending tubes, we muft add the. increafe of expenditure 

 occafioned by this caufe to that which is produced by the acceleration of gravity, and. 

 which we have eftimated in Propofition IV. In afcending tubes, gravity a£b in a contrary, 

 direftion, and confequently its effeft muft be deduced from that of the lateral commu- 

 nication. Experiment VII. relates to afcending tubes. The following relate to other, 

 pofitions. 



Experiment XX. The tube A BEE of fig. 11, Experiment XV. was applied in the place- 

 of the tube B C Q^, in fig. 7. The height of the water in the refervoir above the • 

 lower extremity of the tube was 4 1,5 inches. The four cubical feet of water were emitted, 

 in az'"'. 



I applied the fame conical tube A BFE, fig. 11, to the orifice R, fig. 8, to form an: 

 afcending jet a little inclined from the perpendicular. The height of the water of the re- 

 fervoir above the upper extremity, of the tube was 23 inches. The expenditure of four 

 cubical feet was made in 30", 



The time of the expenditure in Experiment XV. was 25''. And by comparing it with 



the prefent, W£,find nearly V.^T^ ; ^^^ = 25" :. 2a". And V23 : '^32^ = 25" ; 

 30". 



