Prof. Tyndall on Recent Researches on Radiant Heat. 255 



Table {continued). 



Name of vapour. Deflection. 



Wood-spirit 55° ; 55°. 



Methylic alcohol (from Dr. W.) . . 55°- 5; 55° 



(from Dr. H.) . . 63°'5; 64° (impure). 



Ethylic ether 63°-5 ; 63°. 



Absolute alcohol 64°-5 ; 64°'5. 



Ethyl-amylic ether 65°; 65°. 



Sulphuric ether 67°; 67°. 



Propionate of ethyle* 68°; 68°. 



Acetate of ethyle 70° ; 70°. 



Doable brass screen 79°'8. 



These deflections correspond to the following absorptions, 

 omitting decimals : — 



IV. 



Name of vapour. Absorption. 



Bisulphide of carbon 17 



Bichloride of carbon 33 



Iodide of methyle 38 



Chloroform 44 



Benzole 50 



Amylene . 84 



Pure methylic alcohol 84 



Ethylic ether 200 



Absolute alcohol 210 



Ethyl-amylic ether 216 



Sulphuric ether 237 



Propionate of ethyle 252 



Acetate of ethyle 282 



These results, which followed many thousand undescribed 

 experiments, were all obtained before the end of July 1859 ; and 

 I should certainly have published them and many others in ex- 

 terna at the time, had I not felt that the wide circulation the 

 general description of the inquiry had obtained relieved me from 

 this necessity. I wished to impart the last finish to my apparatus, 

 and to pursue the subject with that deliberation and thorough- 

 ness which its difficulty and importance demanded. Not until 

 the close of 1860 was the full account of the investigation drawn 

 up ; and the memoir in which it was embodied bears the receipt 

 of the lloyal Society for the 10th of January, 1861. It after- 

 wards formed the Bakerian Lecture for the year. 



For months I was harassed by the discordant results obtained 

 with gases generated in different ways. The nitrogen obtained 

 from the passage of air over heated copper turnings gave me at 

 first many times the effect of the air itself; that obtained from 



