PHYSICS. 101 



tave. A small movable weight upon one leg, which can 

 be adjusted while the fork is vibrating, and a mirror on 

 the other, complete the apparatus. A second fork, without 

 adjustment, but having a mirror and an electro-magnet, acts 

 conjointly with the first one to produce the curves. 



Decharme has investigated the pitch which bars of various 

 metals and alloys of exactly the same size yield when vi- 

 brated transversely. The rods were twenty centimeters long 

 and one centimeter in diameter, and they were supported at 

 their nodal point, i. e., four centimeters from the ends, upon 

 prisms of cork, and struck with a wooden hammer covered 

 with India-rubber. The pitch varied widely: lead gave 

 only 690 single vibrations per second; while gold gave 970; 

 silver, 1034.6; tin, 1161.3; zinc, 1422; copper, 1642.3; cast 

 iron, 1843.6; wrought iron, 2192.2; steel, 2322.6 ; and alu- 

 minum, 2762. There is thus an interval of two octaves from 

 lead to aluminum. From the data thus given the author 

 calculates the coefficients of elasticity of these metals, which 

 agree very well with those obtained by Wertheim. 



Lootens has studied the phenomenon of air-motion in or- 

 gan-pipes. By means of little pith propellers he has shown 

 the existence in the pipe of cyclonic currents rising on one 

 side of the pipe and falling on the other, the air producing 

 them being that portion of the current which enters the 

 pipe. If the pipe does not speak, this portion mixes with 

 the other portion of the air by which the pipe is blown ; 

 but if it does speak, this cyclonic current does not mix with 

 the other one, but takes a direction on issuing notably more 

 inclined. These results being directly connected with the 

 vibration of the walls of the pipe, the author concludes that 

 this intermittent current, whose vibrations are determined 

 by the walls of the pipe, acts the part of the perforated plate 

 of a siren. 



Ridout has described a simple burner for obtaining a very 

 sensitive flame at feeble gas pressures. A tube five inches 

 long and five -eighths inch wide is closed at one end by a 

 perforated cork, through which slides a piece of tube one- 

 eighth inch wide and six inches long, having the inner end 

 drawn to a jet one-sixteenth inch wide. The inner tube is 

 pushed up, the gas issuing from it lighted, and the tube 

 slowly drawn down. A long steady flame is obtained which 



