302 



MK. N. BOHE ON THE DETERMINATION OF THE 



the jet, c ; (4) the mean radius of the jet, a (which four quantities are connected by 

 the relation V = pcira?); (5) the wave-length, and, finally for the correction, (6) the 

 amplitudes of the waves. 



The density p of the tap-water used was at 1 2 found to be so near 1 (p = about 

 I'OOOl) that by putting p = 1 only errors far below the exactness of the experiment 

 were made. 



The measuring of the discharge presented no difficulty, and could be executed to 

 0'02 per cent, of its value. 



Determination of the Velocity of the Jet.* 



When the jet is formed by a glass-tube, the velocity cannot be exactly calculated 

 by the height of pressure on account of the friction in the tubes. In the present 



Fig. 2. 



investigation a direct method was therefore used to measure the velocity of the jet, 

 the main features of which were as follows : In a fixed point the jet was cut 

 through, at constant time-intervals, by help of a sharp and thin knife, and at the 



* A critical account of methods used in former investigations is to be found in the paper of 

 P. O. PEDERSEN (loc. eit., p. 352). 



