226 Proceedings of the British Association for [Sept. 



tions of this kind have of late largely engaged the attention of some 

 French mathematicians, and the nature of their theories, and the 

 results of the calculations founded on them, deserve to be brought as 

 much as possible into notice." Acting upon these just views, Mr. 

 Challis has accordingly performed for the British Association and for 

 the British public, the important office of reviewing and reporting 

 upon those researches of Laplace, Poisson, and Gauss, respecting the 

 connexion of molecular attraction, and of the repulsion of heat with 

 the ascent of fluids in tubes, which give to his report so much of that 

 foreign character which I have already ventured to ascribe to it ; yet, 

 it is just to add, and, indeed, Mr. Challis does so, that as Newton 

 first resolved the mathematical problem of gravitation, in its bearings 

 on the motion of a planet about the sun, and went far to resolve the 

 same extensive problem in its details of perturbation also, he likewise 

 first resolved a problem of molecular forces, and clearly foresaw and 

 foretold the extensive and almost universal application of such forces 

 to the mathematical explanation of the more varied classes of phe- 

 nomena, and that the theory of capillary attraction, in particular, has 

 received some very valuable illustrations in England from the late 

 Dr. Thomas Young. I ought to mention that a very interesting re- 

 port on the foreign mathematical theories of electricity and magnetism, 

 was read in part this morning to the mathematical and physical sec- 

 tion, by the Rev. Mr. Whewell. The next report after that of Mr. 

 Challis in the volume, is the report I already alluded to, by Professor 

 Lloyd, on the progress and present state of physical optics, respect- 

 ing which I should have much to say, if I did not fear to offend the 

 modesty of the author, and were not restrained by the recollection 

 that he is a member of the same University with myself, and a 

 countryman and friend of my own. I shall, therefore, simply ex- 

 press my belief, that no person who shall hereafter set about to form 

 an opinion of his own on the question between the two theories of 

 light, will think himself at liberty to dispense with the study of this 

 report. I may add that it also, as well as that of IVIr. Challis, draws 

 largely from foreign stores ; but if Huygens was the first inventor, 

 and Fresnel the finest unfolder, and Cauchy the profoundest mathe- 

 matical dynamician, of the theory of the propagation of light by waves, 

 and if the names of Malus, Biot, and Arago, and other eminent 

 foreigners are familiar words in the annals of physical optics, we also 

 can refer among our own illustrious dead to names enshrined in 

 the history of this science, to the names of Newton and Wollaston 

 and Young, and among our living fellow-countrymen and fellow- 

 members of this Association, (unhappily not present here), we have 

 Brewster and Airey to glory of. It should be mentioned that the 

 author of the report has himself made contributions to the science of 

 light, more valuable than any one could collect from the statements 

 in the report itself, and that important communications in that science 

 are expected to be made during the present week, by Professor Powell 

 to a general meeting, and by Mr. MacCuUagh to the physical section^ 

 The remaining reports in the new volume are those by Mr. 

 Rennie on Hydraulics ; by Dr. Henry of Manchester on the laws 

 of contagion, and Professor Clark of Cambridge on animal physio- 

 logy, and especially on our knowledge respecting the blood. Mr* 



