Radiant Heat, and its Conversion thereby into Sound. 485 



The same vibrating atoms are preserved ; but in A they 

 vibrate on the -whole more slowly than in B ; and as the 

 atomic periods of the transparent vapours synchronize best 

 with the slower oscillations, the absorptions in A are con- 

 siderably higher than those in B. Under C are the absorp- 

 tions when the source was a moderate lime-light, produced by 

 coal-gas and oxygen. Under D are the absorptions when the 

 source was the lime-light with its heat gathered up and sent 

 through the exnerimemal tube by a concave mirror; while 

 under E are the absorptions of the heat of the incandescent 

 spiral aided by a rock-salt lens. The absorptions in D and E 

 are somewhat less than those in 0, because the path of the 

 rays was diminished, through the reduction of internal reflec- 

 tion by the mirror and lens. 



With the foregoing results, obtained with the brass experi- 

 mental tube polished within, where the greater portion of" the 

 heat reaching the pile had undergone reflection, are now to be 

 compared those obtained with the silvered tube, where in- 

 ternal reflection was wholly avoided. 



Table IV. 



Wide silvered tube with no reflection. 



L L M M L 



ABC D E 



Spiral Spiral Lime Lime Lime 



dark. bright. bright, moderate, dull red. 



Bisulphide of carbon . . 40 L8 15 1*5 3-3 



Chloroform 5'6 3"0 35 4-3 60 



Benzol 7'0 6*1 4"4 6-5 SO 



Iodide of methyl ... 7*5 5-9 50 65 9-2 



Iodide of ethyl .... 11-3 7'6 6*8 8-5 1L2 



Amylene 15'0 11-8 8"8 12'0 17"3 



Sulphuric ether .... 21 2 17"1 12*5 15-0 25-0 



Acetic ether 260 200 16"3 24-0 32"0 



Formic ether 27"0 21-0 170 25'0 34"0 



The vapour-pressures here were those given in Table IIL 

 Column A contains the absorptions measured when the source 

 of heat was a spiral under incandescence, aided by a rock-salt 

 lens. B contains the absorptions measured with the same 

 arrangement, the spiral being raised to bright redness. As 

 usual, the heat of lowest refrangibility is most absorbed. 

 C contains the absorptions of a tolerably intense lime-light 

 aided by the silvered mirror ; D the absorptions of the same 

 light with its intensity reduced ; while E contains the absorp- 

 tions of the rays from a lime-cylinder heated to dull redness 

 by a steady flame of hydrogen, burning in air, and aided by 

 a rock-salt lens. 



Phil Mag. S. 5. No. 84. Suppl. Vol. 13. 2 



