134 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



or Tyndall makes no comment on their performance, possibly 

 because they were found at once to be inferior. There are 

 many other phenomena connected with sound of which this re- 

 fraction affords an explanation : such as the very great dis- 

 tances at which the sound of battles has been heard, as well as 

 the distinctness of distant thunder. In general, distant sounds 

 originating near the ground are not heard with any thing like 

 their full power by an observer at the same elevation, while, 

 for every step of ascent above the earth, he perceives a cor- 

 responding increase in its distinctness. 12 A, 1873, IX., 513. 



AX OBSERVATION IN ACOUSTICS BY GALILEO. 



Professor Sedley Taylor calls attention to a recent unex- 

 pected discovery in the writings of Galileo, showing that this 

 philosopher was acquainted with the principles of acoustics 

 concerned in the phenomenon of resonance ; and, again, that 

 he devised the earliest known direct experimental determina- 

 tion of the ratio of the vibrations for a known musical inter- 

 val. Galileo relates that he was one day engaged in scrap- 

 ing a brass plate with an iron chisel, in order to remove some 

 spots from it, and noticed that the passage of the chisel across 

 the plate was sometimes accompanied by a shrill whistling 

 sound. On looking closely at the plate, he found that the 

 chisel had left on its surface a long row of indentations, par- 

 allel to each other, and separated by exactly equal intervals. 

 This occurred only when the sound was heard. It was found 

 that a rapid passage of the chisel gave rise to a more acute 

 sound, and the resulting; indentations were closer together. 

 After a number of trials, two sets of markings were obtained, 

 which corresponded to a pair of notes, making an exact fifth 

 with each other; and, on counting the number of indentations 

 contained in a given length of each series, it appeared that, 

 for thirty of the lower sounds, there were forty-five of the 

 higher; whence Galileo inferred that what really determined 

 a musical interval was the ratio of the numbers of vibra- 

 tions performed in equal times by its constituent notes. 12 

 A, 1873, IX., 169. 



THE ELECTRIC DIAPASON. 



A series of highly important experiments, which, though 

 to a great extent technical, promise eventually to lead to im* 



