physics. 583 



the same power of transmitting sound. With coal gas tbe results were 

 quite variable. With carbon dioxide the experiments show that it pos- 

 sesses a much more considerable transmitting power for sound than air, 

 the ratio of distances of the flame being in the two cases 1.32 : 1. The 



mean of the intensities is 1.7459, which is (1.529) ;i . (Comptes Rendu.s, 

 April, 1883, xevi, 1314.) 



Blaikley has presented a paper to the London Physical Society on 

 the velocity of sound in air, using for his measurements a modification 

 of Dnlong's method by means of the wave-length in a lengthened 

 organ pipe. The author -allows for the harmonics of the pipe, which 

 are an important factor. With four tubes lie obtained the following 

 mean results: 1st, diameter 54.1 mm., velocity 329.73 meters per second; 

 2d, diameter 32.5mm., velocity 328.78 meters; 3d, 19.5 mm., 326.9 me- 

 ters; and 4th, 11.7 mm., 324. 5G meters. The mean velocity for all his 

 experiments was about 320 meters. (Nature, November, 1883, xxix, 71.) 



Griveaux has contrived a differential apparatus for determining the 

 relative velocity of sound in solids and in gases. It consists of a tube of 

 glass and a rod of wood of the same length, whose ends, by means of 

 lightly balanced levers, are adjusted to keep closed the two circuits of a 

 differential galvanometer, the currents in which are equal and the 

 needle, therefore, at zero. If, now, a drum be struck opposite the free 

 ends of this rod and tube, the sound will be unequally transmitted, 

 and the galvanometer needle will be displaced in the same direction as 

 when the circuit is opened at the end of the wooden rod. By using the 

 Wheatstone bridge arrangement a galvanometer with a single wire 

 may be used in this experiment. (J. Phys., May, 1883, II, n, 228.) 



Boltzmann has succeeded in photographing sonorous vibrations di- 

 rectly. A thin plate of iron, covering a capsule containing air, is the 

 vibrating body. To its center is attached a very thin strip of platinum, 

 perpendicular to its plane and vibrating with it. This strip is strongly 

 illuminated by sunlight, and its image may be formed on the screen by 

 a microscopic objective. The linear image falling on a cylindrical lens 

 is transformed into a point, which is allowed to fall on a revolving 

 cylinder covered with sensitive photographic paper. On speaking 

 before the vibrating plate the shadow is displaced and a sinuous line is 

 produced on the paper. The vowels give either a simple sinusoid or a 

 combination of two sinusoids. The consonant curves resemble some- 

 what Koenig's figures, given by the letter r. (Ber. AJc. Wien, 1882, 242 ; 

 J. Phys., April, 1883, II, n, 195.) 



An improved apparatus for projecting acoustic vibrations has been 

 described by Eigollot and Chavanon, under the name of a palmoptic 

 capsule. It consists of a hollow paraboloid, over the mouth of which a 

 collodion membrane is stretched. In front of this membrane is a plati- 

 num wire, serving as an axis, on which is a mirror, its plane parallel to 

 that of the membrane. This mirror rests on the end of a small rubber 

 prism attached to the membrane, so that when the latter vibrates the 



