20 Remarkable Phenomena tf fpouilng Fluids \ 



tcntion of afcertaining fome of the moft remarkable efFc£ls of thefe particular modifications \n 

 the direfllon of the fluid filaments, which prefs each other in order to pafs through the orifice. 



Experiment xxxi. In the orifice A C B D, fig. 2i, PI. XXII, vol. II, the two fides A B are 

 parallel to the horizon ; the extremities C D are rounded : the width of this aperture is lefs 

 than two lines, its length 1 8 lines, and the charge 32,5 inches. The fcdion of the dream, 

 which iffues from this orifice, firft aflumes the form E F ; after which, the two extremities- 

 E F, approaching nearer and nearer to fwell the middle part of the feiStion of the ftream, at 4,5 

 inches diftance from the orifice, acquires the quadrangular form G H. The ftream after- 

 wards extends itfelf in the perpendicular dire6lion in the form of a large fan K L. 



I have repeated the experiment by placing the longitudinal axis of the orifice E D vertically. 

 In this cafe the fame phenomena were produced ; E F becoming vertical, and K L horizon- 

 tal, both preferving their form. 



The fluid filaments which, ifiuing out of the orifice, pafs near the two oppofite borders A,B, 

 are very near each other, being convergent, tend to unite at a very ftiort diftance from the 

 orifice itfelf. The filaments C, D, are more remote, and, perhaps, lefs convergent ; they cannot 

 unite but at a greater diftance than the two former. In this cafe, therefore, there are move- 

 ments which tend to form two contradtions, the one nearer, and the other more remote from 

 the orifice. Thefe two contraftions counterbalance each other in part ; their mutual oppofition 

 carries the effedt G H to a diftance five times greater than that of the contratSed vein of a 

 circular orifice, having a diameter of the fame breadth as that of this orifice. 



In this experiment we fee the caufe of a phenomenon, which has been obferved in fome par- 

 ticular cafes by Poleni and others, without giving the explanation. In every orifice of a 

 right-lined figure through a thin plate, the angles of the contra6ted vein anfwer to the fides 

 of the orifice, and the contrary. When the quadrangular orifice has the fituation M N O P, 

 the greateft contradtion of the ftream is made at a greater diftance than in a circular aperture ; 

 it affumes the form and fituation Q_R S T. The rcafon is, that the oppofite angles, M,P, 

 are morere mote from each other than the fides I, V, whence the fame thing happens as in the 

 long orifice A C B D. In the fame manner, the triangular orifice in the fituation X pro- 

 duces a contraflion of the form and in the fituation Z, &c. 



Experiment xxxii. The orifice being the horizontal cleft CD, fig. 21, the place G H, 

 or moft contraiSed point of the ftream, was found to be diftant from the orifice as in the follow- 

 ing table : 



Height of the charge above the orifice C D. 

 Inches. 



32. 5 

 18 

 10 

 6 



Diftance of the greateft contraflion G H. 

 Lines. 



53 

 48 



40 

 36 



The long orifice C D exhibits to us, under an enlarged dimenfion, the diftance of the con- 

 tradted vein irom the orifice. By this means, the foregoing table ihews us, in a very fenfible 



manner, 



