184 ANNUAL OF SCIENTIFIC DISCOVERT. 



ing a violin-bow on the glass, a sound-figure will be formed on the surface 

 of the liquid, consisting of nothing but drops of liquid. If the vessel gives 

 the fundamental note, the figure forms a four-rayed star, the ends of which 

 extend to the four nodal points ; but if the note which the vessel gives be 

 the second higher, the star will be six-rayed; and if the vessel gives still 

 higher tones, other more numerously rayed stars are produced. Poggen- 

 dorjf's Annalen. 



THE POWER OF A BIRD'S SONG. 



When we hear the song of a soaring lark, we may be sure that the entire 

 atmosphere between us and the bird is filled with pulses, or undulations, or 

 waves, as they are often called, produced by the little songster's organ of voice. 

 This organ is a vibrating instrument, resembling in principle the reed of a 

 clarinet. Let us suppose that we hear the song of a lark, elevated to a 

 height of five hundred feet in the air. Before this is possible, the bird must 

 have agitated a sphere of air one thousand feet in diameter; that is to say, 

 it must have communicated to 17,888 tons of air a motion sufficiently intense 

 to be appreciated by our organs of hearing. Prof. Tyndall. 



ON THE TELOCITY OF SOUND. 



It has generally been considered that sound moves at a uniform velocity of 

 1,142 feet per second; and in every book on the subject rules are given by 

 which the distance of any source of sound, such as a firearm or a flash of light- 

 ning, may be ascertained by estimating the number of seconds and fractions of 

 a second which elapse between the ocularly-observed time of the occurrence 

 of the phenomenon and the hearing of the sound which accompanies it. 

 Doubtless many persons have in this manner amused themselves by esti- 

 mating the distance off which certain violent lightning flashes must have 

 been, and have taken comfort from the idea that, if a certain number of 

 seconds have elapsed after the flash has taken place before the thunder is 

 heard, they are safe from its effects; falling into the very common error of 

 mistaking the cause for the effect. The Rev. S. Earnshaw has, however, 

 been engaged in some extremely interesting mathematical investigations 

 respecting the phenomenon of sound, and has arrived at the theoretical con- 

 clusion that violent sounds are propagated far more i-apidly than gentle 

 sounds, and that therefore all reasoning upon the distance of the flash, based 

 upon the lapse of time between it and the thunder, is fallacious. Many 

 instances of this fact are adduced in corroboration of the theory, in which 

 the clap of thunder followed immediately after the lightning, when, judging 

 from the distance which the latter was from the observer, there should have 

 been an interval of many seconds duration. These and similar instances 

 have induced the above-named gentleman to enter upon a mathematical 

 investigation of the theory of sound, and he arrives at the conclusion, con- 

 trary to the hitherto universally received opinion, that there is no limit to 

 the velocity with which a violent sound is transmissible through the atmos- 

 phere, provided the phenomenon which produces the sound be sufficiently 

 violent. Hence, it is probable that there is no sound which is propagated 

 faster than a clap of thunder, its genesis being especially violent. This 

 theory seems also capable of explaining the rumbling, rolling noise of thun- 

 der. It is only necessary to imagine that the sound at its origin is broken 

 up, either by partial interruption or reflection, into several sounds of differ- 



