dependant en the Figure ef the Aperture, 2i 



manner, that the contraftion of the ftream takes place at a greater diftance under ftrong charges, 

 than in thofe which have but little elevation. 



Experiment xxxiii. To the centre of the circular orifice A B, fig. 23, formed in a thin 

 plate, I difpofed, within the refervoir, the cone of metal D G E, with a cylindrical part 

 C F G D, in fuch a manner that the coaejwas moveable along its own axis I V, and its fummit, 

 E, could be protruded more or lefs through the orifice A B, approaching or receding from the 

 point V. The meafures in lines were A B = i8; I £ = 24; D 6 = 27; C D = 8. This 

 apparatus was applied to the orifice P, fig. i, Plate VIII ; the change being 32,5 inches. The 

 refults were as in the following table. 



I intend to repeat and vary this experiment, in order to difcover the caufe of the fihgular' 

 phenomena which it prefents. 



Experiment xxxiv. The orifice being a femi-circle, Plate XXII, fig. 24, vol. II, having the 

 diameter A B, 11,2 lines, I applied within the veflel a plane Q_A B, perpendicular to the 

 plate in which the orifice was made. The line A B was perpendicular to the horizon, and 

 the charge 32,5 inches. The jet deviated in the horizontal dirediion in P F G, departing 

 from the axis C E towards the fide on which the plane Q^P was placed. The angle F C E 

 was 9° 5', and the angle F C G was 36". 7"he vertical feilion of the jet had the form K L, 

 fo that the largeft part of the jet was M. F. The four cubical feet of water iflued out in 206 - 

 feconds. 



The refults of this experiment are analogous to thofe of the experiments xxxi and xxxiii. 



Experiment xxxv. Citizen Borda, in a very interefting memoir*, relates a peculiar pheno- 

 menon, of which he has given a very fimple demonftration, from the principle of the equality 

 of preffure, which fluids exert in every diredtion. It is that, if the extremity of a cylindrical 

 tube be puflied into the interior part of the refervoir, the contradlion of the vein is greater, and 

 the expenditure lefs, than if the fame tube be applied to the fide of the veflel. I have repeated 

 this experiment, and obferved a fimilar refult when the tube was cylindrical from one end to 

 the other, like that made ufe of by the author, and when the water was made to flow out in a . 

 full ftream. I afterwards gave to the interior extremity of the pipe the form A C, fig. 4, Plate 

 VIII, vol, II, of the common contradled veins ; in this cafe, there was no longer any remark- 



* Memoirej de I'Acad. 1766. 



able 



