Prof. Magnus's Hydraulic Researches. 105 



sides of the aperture AD and BC, the shape of the jet remains 

 quite similar to that which is formed without any hindrance ; 

 even if there be placed on each of the narrow sides, close to the 

 edge, high vertical walls, which are many, perhaps a hundi-ed 

 times, broader than these sides of the apei'tui'e. In fig. 15 c 

 the lines PP^ and QQ^ represent the position of such vertical 

 walls or screens near the narrow sides of the aperture ABCD. 

 Only that part of the jet from the orifice to the greatest contrac- 

 tion changes its form and assumes the figure represented in 

 fig. 15 d. The place of the greatest contraction, ef, lies further 

 from the efflux orifice, and the limits of the jet Ae and B/] appear 

 up to this contraction less curved than in the case of the jet 

 formed without these screens. 



49. If screens be used in the manner represented in ground 

 plan by RS and R^S,, fig. 15 e, the jet next to the afflux orifice 

 assumes the form fig. 15/. The boundary lines Ae and B/ near 

 the efflux orifice are almost at right angles. They only begin to 

 converge at a greater distance from the orifice, so that the part 

 ef of the greatest contraction is still further from it than in the 

 preceding case, fig. 15 rf. Below this place of greatest contrac- 

 tion, the form of the jet is quite similar to that represented in 

 fig. 15 a and b. 



50. It follows hence, and the con-ectness of the conclusion 

 has been proved by experiment, that even if an aperture be made 

 in a thick plate, the form of the jet remains almost unchanged ; 

 for when the water issued through a tube which was 20 millims. 

 long, and which had a cross section equal to the elongated aper- 

 ture employed in the thin plate, the jet had just the same form 

 as when the walls set up at the narrow sides of the apei'ture, 

 § 48, were used. Care must be taken that the issuing water 

 quite filled the tube. Then the distance from the aperture to 

 the greatest contraction appeared, as before, longer than in the 

 case of the orifice in the thin metal plate without any walls. 



51. Inusiug the aperture in the thin wall,if the affluxfor the half 

 of one of the long sides, as CD, be prevented, not by a wall, but 

 by a piece of metal plate, E, fig. 16, half as long as the side CD, 

 which is so placed near it, as is represented in fig. 16, a consider- 

 able change in the form of the jet takes place. It appears now 

 spirally wound. It is at the same time deviated from the vertical, 

 and towards that side on which is the piece of metal E. This is 

 attempted to be shown in fig. 16 a and b. Fig. 16 a represents 

 it as seen by one who stands before the long side of the aperture 

 AB, and fig. 16 i as seen by one who stands before the narrow 

 side BC. 



52. For as soon as the liquid has left the orifice, two thick 

 edges Kfi and B/ are formed, as in the case where no hindrance 



PhU. May, S. 4. Vol. 11 . No. 70. Feb. 1856. I 



