Prof. Magnus's Hydraulic Researches. 103 



plate an arrangement was made by which the aperture could be 

 closed. 



Fig. 14, Plate II., represents a section of the middle part of 

 the bottom of the vessel, a quarter of its natural size ; vv/ is the 

 wooden board used to strengthen the bottom, xx/ is the tin plate 

 with its efflux orifice z. This is placed on the brass plate 

 9PPi9r which is soldered at q and q, to the zinc bottom rr,. 

 The aperture of this plate pp^ was closed by means of a brass 

 plate provided with a handle w, which, on its upper side, where 

 it pressed against the plate qqi, was covered with leather. In 

 order to fasten it, two pegs, 7/1/,, were fixed in it horizontally at 

 places opposite each other, which pegs fitted into two hooks oo^. 

 When the plate was turned, the pegs passed out of the hooks, 

 the plate could be removed, and the water flowed out. 



41. The vessel thus arranged stood upon a firm frame of 

 strong wood, l'""75 high. The lower part was joined by sti'ong 

 cross bolts, while the junction at the upper part was effected by 

 a few iron bands. It was thereby possible to observe the jet by 

 full light at the efflux orifice, where its form was particularly 

 interesting. 



In the middle of the four legs of the frame the vessel for the 

 reception of the water was placed. This was unconnected with 

 the frame. 



42. When the water fell in freely, a tolerably loud noise re- 

 sulted ; for the water already fallen in, and through it the vessel 

 itself, were moved. In order to avoid this motion, a board was 

 placed almost vertically in the vessel. As it was placed so that 

 the water must fall on that part of it which was out of the vessel, 

 it slid equably down the board, and neither noise nor any ob- 

 servable motion resulted. 



43. In turning now to the description of jets which issue 

 from differently formed apertures, it might be expected that I 

 should commence with the circular aperture as the simplest. 

 Since, however, the object of the present treatise is the explana- 

 tion of the peculiar forms of jets which proceed from different 

 apertures, I prefer to give the description of the few jets most 

 useful for this explanation in the order which seems most fitted 

 for the attainment of my object. I begin, therefore, with that 

 from a long rectangular orifice. 



Jets from an elongated rectangular orifice. 



44. When an elongated rectangular orifice, 2"6 millims. long 

 by 25 millims. broad, was used, the jet took the form which is 

 represented in Phite II., when all disturbing influences were 

 avoided, and the efflux took place regularly. Fig. 15 a is the 

 view obtained on looking at the jet at right angles to the greater 



