Mr. Wheeler's Experiments in Photometry. 439 



was also definite in its magnetic action (366. 367. 376. 377.); 

 and, though this result was not pursued to any extent, I have 

 no doubt that the success which has attended the development 

 of the chemical effects is not more than would accompany an 

 investigation of the magnetic phenomena. 

 Royal Institution, Dec. 31, 1833. 



LXI. Experiments and Observations on the Application of 

 Photometry to certain Cases connected with the Undulatory 

 Theory of Light. By J. H. Wheeler, Esq.* 



n^HE interest inspired by the discussions which have arisen 

 -*- within the last few years on the relative claims of the 

 corpuscular and undulatory theories of light, has been pro- 

 ductive of inestimable benefit to science. To Mr. R. Potter 

 the scientific world is certainly indebted for bringing forward 

 the first formidable objections, grounded on the application 

 of mathematical reasoning, to highly original experimental evi- 

 dence ; and whatever opinion may be entertained of the result 

 of the controversy, and the light thrown upon the question by 

 the various replies and rejoinders which have appeared, the 

 excellence of Mr. Potter's experimental labours, and the pro- 

 found ability with which he has maintained his side in the 

 controversy, cannot be too highly appreciated. And it emi- 

 nently deserves to be remembered, that with the most perfectly 

 philosophic love of truth, he has in a more recent paper can- 

 didly allowed the result of a long and laborious series of ex- 

 periments to be in favour of the theory he set out by op- 

 posing. (See this Journal, November 1833.) Still, however, 

 some of the principal objections brought forward by this gen- 

 tleman remain unanswered. I allude to those which depend 

 upon the calculated intensities of light in certain cases, which 

 are found totally to disagree with the observed intensities as 

 determined by his highly ingenious and admirably conducted 

 experiments, depending on the application of photometry, 

 which have appeared in several Numbers of this Journal. 



Having felt from the first a deep interest in the subject, and 

 especially as connected with photometry, I have ever since 

 the publication of Mr. Potter's experiments been engaged, 

 as much as my other avocations would allow, in attempts to 

 repeat and verify them, and, if possible, to extend their ap- 

 plication to other cases. My labours hitherto have met with 

 but limited success, partly from the want of sufficient experi- 

 mental skill, but chiefly from some apparently insuperable 



* Communicated by the Author. 



