On the lattral Communtcatton of Mot'mi In Fluids, ' 423 



The general theory is the fame for both thefe forms of tubes ; but the lofs of living 

 force is greater in the cylinder, and the efFeft of the communication of motion in thefc 

 tubes cannot approach its maximum as in the cone. Let the tube A C N M, fig. 5. PI. VIII. 

 of the prefent volume, have the form of the contrafted vein in A C F D ; the cylindrical 

 part G I N M has its diameter MN, greater than D F. By the reafoning made ufe of in 

 the preceding propofition, it is proved, that the lateral communication of motion tends to 

 produce a vacuum in the folid zone R O Y S X QJT Z. If the communication of motion 

 in this tube were completely made, it would follow, that the preflure of the atmofphere 

 would increafe the velocity of the contraded vein in the ratio of D F^ to MN". 



But the form itfelf of the cylindrical pipe always deftroys a notable part of the efFe£l : 

 for the fluid filaments A D, in turning through the curve D R, proceed brifkly to ftrike 

 the fides of the tube G M at R, where they lofe part of their motion. In the fpace D G R 

 eddies, or circular whirls, are produced, as in a bafon which receives water by a channel. 

 Thefe eddies are, to a certain extent, a failure of the effe£t, and retard the efflux of the 

 ftream. A much lefs increafe of the expenditure takes place in the cylindrical tube than 

 would anfwer to the ratio of D F^ to M N-. 



Experiment XVIII. — A notion may be formed of thefe internal fhocks and eddies in the 

 cylindric tube, and their effefts on the efflux of the fluid, if attention be paid to the fol- 

 lowing table of the expenditure through the diiferent additional tubes in the horizontal 

 pofition. All thefe tubes have the diameter of their two extremities =18 lines ; they were 

 all provided with the conical tube of the form of the contra£led vein at their inner extre- 

 mity, excepting that of fig. 6. The charge was always 32-5 inches above the centre of 

 the orifice. 



Viable of the Times employed in difcharging Four Cubic Feet of Water through the different 



Adjutages, 



Through the orifice in a thin plate, - - - 41". 



Through the fimple tube of fig. 6. - - , 31", 



Through the tube of the form of fig. 5. - - 31". 



After having amended (adouci) the conical divergent part, D F I G, 



of the fame tube, - - - - 30". 



Through the tube fig. 9. - - - - V-"-^ 



Through the conical tube of the form fig. 10. - - 27".J 



Through the tube fig. 5. the portion G I N M being 23.5 lines 

 in diameter, and 84 in length, the reft as before, - 27''. 



It may perhaps be demanded, whether, in the internal part of the fimple cylindric tube 

 K L V of fig. 6. there be the fame augmentation of velocity, and the fame contra£l:ion of 

 the ftream, as in the compound tube of fig. 5. ? By reafoning according to the principles 

 we have eftablllhed, I think, i. That in the fe£lion K L of fig. 6. there is the fame increafe 

 cf velocity as we have feen (Prop. II.) take place in the feclion A C of fig. 5. The direc- 

 tion of the fluid particles which pafs through thefe two feftions mud be the fame in both . 

 cafes, becaufe this diredion can depend only on the impulfe received within the refervoir, 

 which is the fame in both. 2. In fig. 6. the fluid particles, after having pafled through the 

 fettion K L, begin immediately to experience the effe£l of the lateral communication of 

 motion. They muft therefore deviate laterally through the curve L .f 2, before they ar- 



3 I a rive 



