Radiant Heat, and its Conversion thereby into Sound. 513 



Table VI. — Gases. 



Name of Gas. ^^Sim^' 



Chloride of methyl 350 



Aldehyde 325 



Olefiant gas 315 



Sulphuric ether 300 



Nitrous oxide 198 



Marsh -gas . 164 



Carbonic acid 144 



Carbonic oxide 116 



Oxygen 5 



Hydrogen 5 



Nitrogen 5 



Dry air , 5 



Humid air at 50° C 130 



Sulphuric ether is here inserted with the view of connecting 

 this Table with the last. Of all gaseous bodies hitherto 

 examined, chloride of methyl is the most energetic absorber 

 and the most powerful sound-producer. After it comes alde- 

 hyde, with a boiling-point of 21° C. The figure 5 attached 

 to the elementary gases and to dry air expresses, not ab- 

 sorption of radiant heat, but expansion, due to contact 

 with the slightly warmed apparatus. The nitrous oxide em- 

 ployed was derived from an iron bottle, in which it was pre- 

 served for medical purposes. In some of my experiments 

 marsh-gas showed itself a better absorber than nitrous oxide. 

 This, for instance, was the case in experiments made in the 

 spring of 1880 with the manometer. The sample of marsh- 

 gas wherewith the foregoing result was obtained was very 

 carefully prepared in our chemical laboratory. 



The temperature of 50° C. in the case of humid air was 

 obtained in a wooden shed erected in our laboratory. The 

 shed is traversed by two tubes of sheet iron 4 inches in 

 diameter, which carry the heated air and products of combus- 

 tion from two large ring burners. It is 8' &' long, 4/ ?>" wide, 

 and 7 feet high. The temperature of the air within it can 

 be readily raised to 60° C. In the experiment recorded in 

 Table VI. the air was taken from the outside laboratory 

 through a tube passing through the wooden wall of the shed. 

 It was caused to bubble through water contained in a large 

 flask which had been permitted to remain for some time in 

 the warm shed. The mixed air and vapour entered the manc- 

 meter-tube at a temperature some degrees lower than that of 

 the tube itself. Closely examined, all parts of this tube were 

 bright and dry when the vapour-laden air was within it. On 



