Experlmtnts on the lattral CommunUathn of Motion in Fluids. 175 



neverthelefs was more abundant, in the fame proportion as through the fimple cjlindric 

 tube. It follows, therefore, that the velocity of the fe£lion D F, and of the whole conoid 

 A C D F, muft have been greater than that of the contradted vein from a thin plate ; and it 

 remains to be (hewn what was the caufe of this augmentation of velocity which takes place 

 within the tube, and does not manlfeft itfelf externally. 



That the conical tube ACD F does not itfelf caufe any augmentation of expenditure, is 

 evinced by the following . 



Experiment 4. The conical tube A C D F, from which the remaining part D G MN I F 

 was feparatcd, was. applied to the orifice P. The four cubic feet were emitted in 42 feconds, 

 which is the time of the expencc through the orifice itfelf A C in the thin plate, with the 

 difference of one fecond only. This flight variation arifes from its"being almoft Impoffible to 

 make the tube A D C F perfe£lly of the form of the natural contra6led vein. 



Propojition 3. The preffure of the atmofphere increafes the expence of water through a 

 fimple cylindric tube, when compared with that which iflues through a hole in a thin plate, 

 whatever may be the direftion of the tube. 



It has long been known, that a heavy fluid which moves in a defcending C)lindric pipe 

 tends to accelerate its motion. The inferior parts tend to feparate themfelves from the 

 fuperior, and by that means caufe the prefTure of the atmofphere to increafe the velocity of 

 the fuperior parts. This fucceffive acceleration of gravity cannot take place in an horizon- 

 tal or afcending pipe. We fhall neverthelefs find that the prefTure of the atmofphere adts 

 even in thefe laft Ctuations to increafe the velocity of fluid within the pipe. Certain 

 queftions of legal right, which arofe in my country, refpeifling the quantity of water fun- 

 plied by a pipe for watering lands (canal d'arrofement) dire£led my attention to this objeiSf, 

 In the year 1791 I made the following experiments publicly in the Theatre of Natural Phi- 

 lofophy at Modena : 



Experiment 5. To the aperture P, fig. i, I applied a cylindrical pipe 54 lines in length 

 and 18 in diameter. At the diflance of nine lines from the interior orifice P, twelve fmall 

 holes were made, in its circumference. When thefe fmall holes were open, the four cubic 

 feet ifTued out in 41 feconds, in the fame manner as through a thin plate. Not a fingle drop 

 pafTed through any of the holes, and the ftream did not fill the tube. The holes were thea 

 clofed one after the other with wet fkin. As long as there was one hole open the expence con- 

 tinued the fame ; but when at laft all the twelve holes were well clofed, the fluid ftream 

 ifTued out in a body which filled the pipe, and the four cubic feet were emitted in 31 fecond?. 

 Experiment 6. To the cylindric tube K L B, fig. 6, 18 lines in diameter and 57 lines lon:^, 

 was joined the glafs tube QJl S T, at the diftance of eight lines from the interior orifice K. 

 The glafs tube v.as plunged in coloured watef contained in the vefTel T. When this ap- 

 paratus was applied to the aperture P, fig. I, the four cubic feet of water flowed out in 31 

 feconds. The coloured liquid T rofe in the tube T R as high as S> at the height of 24 

 inches above the furface T. 



The branch RT of the glafs tube was (liortened fo that RT was only fix inches lon^Gr 

 than RQ. The efHux being then permitted to take place, the coloured liquor of the vefTel 

 T rofe through the tube RT, and mixed with the water which flowed from the refervoir 

 through KV, both of which flowed out at V, and in a Ihort time the vefTe! T w-tb 

 emptied. 



I repealed 



