ARGON, A NEW CONSTITUENT OF THE ATMOSPHERE. 35 



between 80 and 100 atniospberes, and cooling to 90° by means of boiling nitrons 

 oxide, no a[i[>eaiance of li(|iiefacti()n could l)e observed. 



Further experiments in this direction are in contemplation. 



14. TiiK Ratio of the Specific Heats of Argon. 



In onler to gain knowledge regarding the elementary or compound nature of 

 argon, experiments were made on the velocity of sound in it. It will be remem- 

 beied that from the velocity of sound, the I'atio of tlie sj)ecili(; heat at constant 

 pressure to that at constant volume can be deduced by means of the equation 



e Cp 



nA. = V = N-(i + «t) — 



d C, 



where X is the wave length of the sound, v its velocity, e the isothermal elasticity, 

 d, the density, (1 + a t) the temperature-correction, Cp the specific heat at constant 

 pressure, and C^ that at constant volume. In comparing two gases at the same 

 tempei-ature, each of which obeys Boyle's law with sufficient approximation, many 

 of these terms disappeai', and the ratio of specific heats of one gas may be deduced 

 from that of the other, if known, by the simple proi)ortion 



A.2 d : A'= d' :: 1.41 : x 



where foi- examide A and d refer to air, of which the ratio is 1.41, according to 

 observations by Rontgeu (1.4053), AViillner (1.4053), Kayser (1.4106), and Jamiu 

 and Richard (1.41). 



The apparatus ado])ted, although in ]>i'iiK-iple the same as that usually em- 

 ployed, differed somewhat fi-om the oi'dinary pattern, inasmuch as the tube was a 

 narrow one of 2 mm. l)or(', and tlie vibrator consisted of a glass rod, sealed into one 

 end of the tube, so that about 15 cm. projected outside the tube while 15 cm. was 

 contained in the tube. By rubl)ing the projecting i)art longitudinally with a rag 

 wet with alcohol, vibi'ations of exceedingly high pitch took place, causing waves in 

 the fas, which I'esiistered their nodes by the usual device of lyco})odium powder. 

 The temperatui-e was that of the atmosphere and varied little from 17°.5 ; the pres- 

 sure was also atmospheric, and varied only one millimetre during the experiments. 

 Much of the success of these experiments depends on so adjusting the length of the 

 tube as to secure a good echo, else the wave-heaps ai'e indistinct. But this is easily 

 attained by attaching to its open end a piece of thick-walled india-rubber tubing, 

 which can be closed by a clip at a spot which is found experimentally to produce 

 good heaps at the nodes. 



