﻿26 M. 0. E. Meyer on the Heating of a 



still a residue of gas. This gas is partially absorbed by bro- 

 mine, not entirely. The residue appears to be chloride of me- 

 thyle. The liquids condensed both on the surface of the water 

 and in the U-tube were obviously for the most part olefines. They 

 began to boil below zero (Cent.), and probably boil at all tempe- 

 ratures up to about 60°, when the distilling vessel was found to 

 be dry. They appeared to be a mixture of various olefines. 

 This reaction apparently resembles closely that with the oxalate 

 of amyle. 



London Institution. 



IV. On the Explanation of Stewart and Tait's Experiments on 

 the Heating of a Disk rotating in a Vacuum. By Oscar Emil 

 Meyer*. 



TN a previous paper f I have already briefly discussed the expe- 

 riments on the heating of a disk in an exhausted space 

 which Messrs. Stewart and Tait laid, in June 1865, before the 

 Uoyal Society of Londonf y and I then expressed the opinion that 

 the agitations which are communicated to the rotating disk by 

 the wheelwork are the chief cause of the heating. I revert to 

 the subject once more, because the gentlemen in question have 

 published another paper on the subject§, in which it is proved that 

 the cause of the heating is to be sought neither in terrestrial 

 magnetism, nor in conduction, nor radiation of heat, nor in the 

 surrounding air. I think, as I have already said, that the cause 

 lies in the agitations caused by the wheelwork. 



I should not consider it worth while to elucidate this subject 

 to the readers of the Annalen, if, with the aid of the explana- 

 tion in question, the experiments did not enable us to calculate 

 the coefficient of thermal radiation of the disk in absolute measure. 

 We find in this manner a number which agrees most completely 

 with a formula which Professor Neumann, of Konigsberg, has 

 most kindly communicated to me. This formula is based on 

 the observations of Dulong and Petit on the law of cooling 

 and an observation which he himself has made. The agreement 

 between the results obtained in these different ways affords the 

 conviction not only that the explanation of Stewart and Tait's 

 observation is correct, but also that the value in absolute measure 

 obtained for the thermal radiation is undoubtedly accurate. 



* Translated from a separate impression, communicated by the Author, 

 of a paper published in Poggendorff's Annalen, vol. exxxv. p. 285. 

 f Pogg. Ann. vol. exxvii. p. 380. 



% Proc. Roy. Soc. vol. xiv. p. 339. Phil. Mag. S. 4. vol. xxx. p. 314. 

 § Proc. Roy. Soc. vol. xv. p. 290. Phil. Mag. S. 4. vol. xxxiii. p. 224. 

 || Ann. de Chim. et de Phys. vol. vh. (1817). 



