390 Proceedings of the British Association. 



knowledge of the history and nature of comets. Professors 

 Whewell and Hamilton also took a discursive view of the co- 

 metary world in their usual characteristic manner. 



The Association then adjourned, and the President intimated 

 that the next evening meeting would take place in the same 

 room and at the same hour. 



Wednesday, \Qth September. 



MORNIKG UNIVERSITY. 



Section A. — Mathematics and General Physics. 



The Rev. Dr Lloyd, Provost of Trinity College, Dublin, having 

 been called to the Chair, Professor Lloyd read to the Section a 

 portion of his report on physical optics. 



M. Arago offered a few observations on some statements contain- 

 ed in that report, chiefly with reference to the hypothesis of trans- 

 versal vibrations, and advocated the claims of Dr Thomas Young, 

 as the first to propose it. 



Mr Whewell read a paper by M. Challis, entitled " Theoretical 

 Explanations of some facts relating to the composition of the Co- 

 lours of the Spectrum." Mr Whewell also offered some sugges- 

 tions regarding Sir John Herschel's explanation of dispersion, ac- 

 cording to the undulating theory. Sir D. Brewster objected to the 

 validity of this explanation ; his objections being grounded on the 

 phenomena of the dark bands in the light transmitted through ni- 

 trous acid gas, and their alteration with the increase of tempera- 

 ture. 



Professor Powell handed in a short paper " On the Achroma- 

 tism of the Eye," in continuation of a paper contained in the last 

 volume of the British Association. 



Professor Powell then gave a brief view of the explanation of 

 dispersion of light in the undulatory theory, as afforded by the ma- 

 thematical analysis of M. Cauchy, and stated a condition which 

 seemed necessary to the validity of this explanation. 



Mr Whewell, Professor Hamilton, and Dr Robinson also made 

 some observations on the same subject. 



Professor Phillips then read the second report of the result of 

 twelve months* experiments on the quantity of rain falling at differ- 

 ent elevations above the ground, made by himself and Mr Gray. 



Sir Thomas Brisbane made some observations on an anomaly in 



