90 Transactions of the 



weight of ozone ; his results were not, however, satisfactory. 

 It is generally considered to be 24. 



The President complimented Ogle on the ability shown by 

 him in the preparation of the foregoing Paper. G. P. Rod- 

 well, Esq., P.R.A.S., F.C.S., having also spoken in laudatory 

 terms of Ogle's Paper, made some interesting remarks upon 

 'Acoustics,' of which the following is an abstract : — ' A mass 

 of matter in a condition of stable equilibrium, when disturbed 

 by the action of an external force, tends to return to its 

 original condition. Example of the pendulum, alternating 

 motion across a position of rest, vibrations, oscillations, 

 waves, undulations, &c. 



' Vibrations in solids, liquids, gases. — General character of 

 each. Modes of producing vibrations. Parts of a wave, how 

 distinguished — length, depth, height, breadth, depression, 

 elevation. Nature of sound. Interference of sound, cause 

 and effect. Organ pipes, tuning forks, &c. 



' Tartini's Beats. — It has been sho^vn by Weber, that if we 

 rotate a tuning fork, there are four positions in which the 

 sound disappears. If we look do'SNTi upon the prongs of a 

 tuning fork, we may draw lines indicating where the waves 

 generated by the tuning fork interfere ; and these lines are 

 hyperbolic curves. Let us take a tuning fork furnished ^vith 

 a resonance box, and cause it to vibrate ; it will emit a clear, 

 even note. Now let us place the fork with its box on a 

 whirling table, and cause it to rotate rapidly; immediately 

 beats are perceived, which of course vary in frequency of 

 recurrence with the rapidity of revolution. In addition to 

 the cause pointed out by Weber, may it be possible that in- 

 terference results from a second cause '? For let a prong A 

 produce a series of waves in a line a h, and let the fork be 

 rotated with such a velocity that when A returns to its 

 original position at one end of the line a b, the waves, which 

 it now produces meet the waves which it before produced in 

 such a manner that a depression of the former coincides 

 with an elevation of the latter (or vice versa) and hence in- 

 terference. It may be worth the attention of the Society to 

 enquire whether such a condition be or be not possible, and 

 whether it may partly account for the effects observed.' 



