6 Prof. Magnus on the Motion of Fluids. 



d and m and very near to d. "When water was poured through 

 mn none of it escaped at e, but the whole fluid which thus en- 

 tered was immediately pressed backward to k ; and this also 

 occurred when the width of the tube de was pretty considerable. 

 The position of the point k, to which the water in the tube 

 recedes before the jet, varies according as the water moves ex- 

 actly in the axis of the tube, or a little above or below it. But 

 setting this aside, the position is determined both by the mo- 

 mentum of the jet and that of the water which seeks to escape 

 from the vessel A. Hence if the pressure in A vai-ies, if, for 

 instance, the water in this vessel rises while the pressure of the 

 small jet remains constant, the point k will approach nearer to 

 the end e. 



If, on the contrary, the level of the water in A remains con- 

 stant, so that both pressures remain unaltered, the point k where 

 the water masses meet each other varies with the pressure of 

 the air at this point. 



13. In the T-shaped tube demn, fig. 8, which is connected at 

 d with the vessel A, the narrow tube/^, through which the small 

 jet issued, was so introduced that the end /lay near to m. The 

 orifice at g was then squeezed air-tight upon the cork e, and at 

 n was attached a tube which communicated with a large empty 

 bottle B. From the latter proceeded a bent tube op, the lower 

 end of which dipjjed into a cylinder filled with mercury or some 

 coloured fluid. When the level of the water at A was preserved 

 constant, the fluid ascended in the tube op, inasmuch as the air 

 was carried forward by the water at k; but according as the 

 mercury ascended, the point k, where the small jet met the 

 water, approached m more and more ; and on reaching this point 

 the portion ?«/ became filled mth water which ascended in mn. 

 It is evident that the foaming here ceased. 



It is hardly necessary to state that the result was the same 

 when the bottle B was omitted, and the tube from n was carried 

 direct into the mercury ; but in this case the various actions 

 occui'red so quickly that it was impossible to follow them. 



14. If the vessel containing the mercury be also omitted, so that 

 the pressure of the atmosphere acts upon the water in the tube 

 mn, and if the narrow tube fy, through which the jet passes, be 

 changed for a wider one, the latter may be so chosen that no air 

 shall pass in by m, but that the entire tube de shall remain filled 

 with water. By a certain ratio of the diameters of the tubes _^ 

 and ed, the water in the tube mn will stand lower than in the 

 vessel A. The pressure therefore exerted at m will be less than 

 that at d. If the tubc^ be chosen mder, the fluid will rise in 

 mn ; and by a projier ratio of the diameters, can stand therein 

 much higher than in the vessel A. 



The same result can be obtained if, instead of altering the tube 



