Radiant Heat, and its Conversion thereby into Sound. 511 



its suspended matter was allowed to bubble through the 

 liquid in the test-tube, and to pass thence into the manometric 

 tube. To spare the oxygen in the gas-holder it was cut off 

 during the interval between two consecutive experiments, the 

 coal-gas being kept continually alight. When the manometric 

 tube was filled, which was always accomplished through an 

 orifice of fixed dimensions, the oxygen was turned on, and 

 the cylinder was allowed to remain for one minute under the 

 action of the intensified flame. During this time a double 

 silver screen S intercepted the radiation. At the end of a 

 minute this screen, which moved on an hinge, was withdrawn, 

 the beam then passing through the mixed air and vapour. 

 The liquid standing in the adjacent leg of the narrow U tube 

 was immediately depressed, that in the opposite leg being 

 equally elevated. The rise of this latter column above its 

 starting-point, marked zero on a millimetre-scale, was accu- 

 rately measured. Double this rise gave the difference of level 

 in the two legs of the U; and this "water-pressure" expressed 

 the augmentation of elastic force by the absorption of radiant 

 heat. 



Here follow a certain number of the measurements which 

 have been thus made. They do not comprise the whole of 

 the substances examined. 



Table Y. — Vapours. 





Increase of Elastic Force by 



Eadiant Heat. 







Boiling- 



Mean water 



- Character 





Name of Liquid. 



point. 



pressure, 

 millim. 



of sound. 



1. 



Sulphuric ether . 



. 35 



300 



Yery strong 



2. 



Hydride of amyl . 



. 30 



279 



)) 



3. 



Acetone. 



. 58 



267 



)j 



4. 



Bromide of ethyl . 



. 39 



264 



55 



5. 



Formic ether . . 



. 55 



261 



55 



6. 



Acetic ether . . 



. 74 



248 



55 



7. 



Acetal .... 



. 104 



237 



55 



8. 



Chloride of allyl . 



. 46 



235 



55 



9. 



Iodide of methyl . 



. 45 



233 



55 



10. 



Dichloride of ethideL 



e . 57 



217 



Strong. 



11. 



Nitrate of ethyl . 



. 86 



208 



55 



12. 



Nitrite of amyl . 



. 99 



205 



55 



13. 



Chloride of butyl . 



. 69 



185 



55 



14. 



Butyric ether . 



. 121 



183 



}■> 



15. 



Formic acid . . 



. . 99 



180 



55 



1(3. 



Valeral .... 



. . 100 



172 



55 



17. 



Valerianic ether . 



. . 144 



168 



55 



18. 



Acetate of propyl . 



. . 102 



166 



55 



19. 



Methvlic alcohol . 



. . — 



162 



55 



