342 PHYSICS. 



luminous ones, and calorescence, applied by Tyndall to the conversion 

 of ultra-red rays into luminous ones — the term calcescence having been 

 previously proposed by Akin. The word sonorescence, however, to 

 make the analogy exact, should be taken to signify the conversion of 

 sound into luminous rays, and not the reverse effect, for which it is pro- 

 posed. {Natw-e, May 19, 1881, xxiv.) 



Martini has determined the velocity of sound in chlorine gas by 

 means of a resonant column: A glass tube 0.4 meter long and 2 centi- 

 meters diameter, fixed vertically, communicated below by means of a 

 rubber tube, with a second vertical tube adjustable in height, the bead 

 contaiuiug sulphuric acid. When this second tube was raised or low- 

 ered the length of the column of gas could be varied so as to reinforce 

 a certain fixed tone. The first tube being graduated, the length of the 

 column was easily found, and a simple calculation gave the velocity. 

 After verifying the method with carbon dioxide, and hyi^onitrous oxide, 

 the author found 206.4 meters as the velocity of sound in chlorine at 

 zero. '{Nature, 61, May 19, 1881, xxiv.) 



Eobinson has described an experiment which he claims as proof that 

 a sound wave can be polarized. An L-shaped tube 1 inch in diame- 

 ter and 3 inches in length, made of tin, had a portion of the joint re- 

 moved and a piece of membrane, making equal angles with the two 

 branches, i)ut in its jDlace. This angle was obtained from the optical 

 principle that the tangent of the polarizing angle is equal to the ratio 

 of the velocities in the two media; in the present case, to the ratio 

 1420 : 1125, the velocities in coal gas and air respectively. A series 

 of these bent tubes were connected together so that by turning them 

 round each other the membranes could be placed either all parallel to 

 each other or all perpendicular. At the two ends were membranes clos- 

 ing the tubes. After filling the tube with coal gas, it was found that 

 no effect could be obtained with sound itself. A pulse was therefore 

 produced by the fall of a ball suspended by a thread against the end 

 membrane, the recei^tion of the pulse being recorded by the motion of 

 a similar ball at the other end. In one series of eighty experiments the 

 mean detiection when the tubes were jjarallel was 0.47, and when per- 

 pendicular 5.43, a difference of 16.1 i)er cent. Ko difierence was observed 

 when the tube was filled with air. Concediug this result to be actual, 

 it would seem more probable that it is due to some mechanical iJecul- 

 iarity of the apparatus rather than to the jjolarization of a longitudinal 

 wave. But the more sweeping conclusion of the author, that all vibra- 

 tions in extended media are longitudinal, and become transversal when 

 polarization takes place, cannot at all be conceded on the basis of the 

 experiments which he has made. {J. Frank. Inst., March, 1881, III, 

 Ixxxi, 201; Am. J. Sci., June, 1881, III, xxi, 501.) 



Eeuleaux has recorded a singular case of the production of sound by 

 natural causes, observed while hunting in the lioderbacherthal, near 



