88 FRAGMENTS OF SCIENCE 



unison. If a morsel of wax, not larger than a pea, be 

 placed on one of the forks, it is rendered thereby power- 

 less to affect, or to be affected by, the other. It is easy 

 to understand this experiment. The pulses of the one fork 

 can affect the other, because they are perfectly timed. A 

 single pulse causes the prong of the silent fork to vibrate 

 through an infinitesimal space. But just as it has com- 

 pleted this small vibration, another pulse is ready to strike 

 it. Thus, the impulses add themselves together. In the 

 five seconds during which the forks were held near each 

 other, the vibrating fork sent 1,280 waves against its neigh- 

 bor, and those 1,280 shocks, all delivered at the proper 

 moment, all, as I have said, perfectly timed, have given 

 such strength to the vibrations of the mounted fork as to 

 render them audible to all. 



Another curious illustration of the influence of syn- 

 chronism on musical vibrations, is this: Three small gas- 

 flames are inserted into three glass tubes of different 

 lengths. Each of these flames can be caused to emit a 

 musical note, the pitch of which is determined by the 

 length of the tube surrounding the flame. The shorter 

 the tube the higher is the pitch. The flames are now si- 

 lent within their respective tubes, but each of them can 

 be caused to respond to a proper note sounded anywhere in 

 this room. With an instrument called a syren, a power- 

 ful musical note, of gradually increasing pitch, can be pro- 

 duced. Beginning with a low note, and ascending grad- 

 ually to a higher one, we finally attain the pitch of the 

 flame in the longest tube. The moment it is reached, the 

 flame bursts into song. The other flames are still silent 

 within their tubes. But, by urging the instrument on to 

 higher notes, the second flame is started, and the third 



