RECORDS 495 



hearing. He overcame the effect of irregular disturbing reflected 

 and diffracted waves by using sound of considerable intensity and 

 a flame only slightly sensitive. The sound after passing between 

 the teeth of a rapidly revolving wheel, fell on a concave spherical 

 mirror made of wood some distance away, and was reflected back 

 through the teeth at the opposite end of a diameter of the wheel, 

 and came to a focus on a sensitive flame just behind the wheel. 

 The author Grave a neat demonstration of the working of the 

 apparatus and showed with great ease how with increasing speed 

 of the revolving wheel the flame was alternately shielded from 

 and exposed to the sound. The slightest disturbance of the 

 adjustment of the mirror threw the flame away from the mirror 

 in a marked manner. He stated that the method could prob- 

 ably not be used to compete with other accurate methods here- 

 tofore employed, but it supplied a beautiful illustration of Fizeau's 

 method of measuring the velocity of light. 



Prof J. K. Rees gave an interesting account of some of the 

 scientific instruments at the Paris Exposition. The great tele- 

 scope was not finished, although this fact was not yet generally 

 known, and it was impossible to tell yet whether it was to be a 

 success or not. The German exhibit was superb. The Ger- 

 mans had a method, which ought to have been generally adopted, 

 of arranging the instruments with one kind b)^ the different 

 makers in one case, instead of a complete line by each maker 

 in a case by itself An ingenious modification of Foucault's 

 pendulum was seen at the Paris obser\^atory. It was only one 

 meter long, but it showed the fact of the rotation of the earth 

 after the lapse of fifteen seconds. 



Professor Hallock described a peculiar lightning discharge he 

 had observed at Lake Champlain. The flash came unexpectedly 

 from a cloud about two miles from where the main shower was 

 falling. It struck on a mass of rock, and on examining this it 

 was found that instead of there being one or a few places where 

 the lightning had struck, it was covered with innumerable little 

 spots, each one indicating where a part of the flash had struck. 



WM. S. Day, 



Secretajy. 



