ON WAVES. 



377 



Table XXII. 



Observations oti the Vehcity, Distance, and Divergence of Waves of the 

 Tliird Order. 



Column A contains the time in which the disturbing body, a wire of one- 

 sixteenth of an inch in diameter, was drawn with a uniform motion along 

 distances of 12 feet each ; each experiment being frequently repeated. 



B and C are the corresponding velocities of the disturbing body. 



D, E, F are the number of complete waves, reckoning from hollow to hol- 

 low, contained in each successive inch from the centre of the disturbing 

 wire, formed in the direction of the motion of the wire. 



G. The numbers in this column are measures of the divergence of the first 

 wave from the path of the exciting wire, measured at 25 inches behind that 

 wire, and of course these numbers are tangents to the radius 25 for the angle 

 of divergence. 



H contains the angles deduced from the numbers in G. 



Observations on the Capillary Waves. 

 See Plate LVII. 



The crowding of the ridges is not the only phaenomenon that accompanies 

 the increase of velocity of the moving point ; the first wave, that whose ridge 

 is in the focus, scarcely differs from a sfraight line, and the angle which it 

 makes with the path of the disturbing point, diminishes with the increase of 

 velocity ; the divergence of the first wave from the path of the exciting body 

 is given in another column by an observation of the distance of the wave 

 from that path at a given distance behind the body. These numbers show 

 that the velocity of the wave, taken at right angles to the ridge, is nearly that 

 of the free wave. This angle therefore becomes an index of the relation of 

 the velocity of disturbance to the velocity of wave propagation. 



The form of the wave ridges appears to be nearly that of a group of confocal 

 hyperbolas, the exciting body being in the focus. 



I have found the numbers given in columns C, D and E, to be determined 

 by the velocity of the disturbing body, and quite independent of its size 

 and form. But while I have found the number of ridges in an inch at a 

 given velocity to be thus invariable, I have not found the number of inches 



