Professor Faraday [May 3, 



Visitors. 



Neil Arnott, M.D. F.R.S. 



George J. Bosanquet, Esq. 



Archibald Boyd, Esq. 



John Charles Burgoyne, Esq. 



George Busk, Esq. F.R.S. F.L.S. 



Rev. Charles John Fynes Clinton, M.A. 



Edward Enfield, Elsq. 



Gordon Willoughby James Gyll, Esq. 



John MacDonnell, Esq. 



Edmund Macrory, Esq. M.A. 



James Nasmyth, Esq. 



Henry Minchin Noad, Esq. F.R.S. 



George Stodart, Esq. 



The Viscount Templetown. 



Arthur De Noe Walker, Esq. 



WEEKLY EVENING MEETING, 



Friday, May 3, 1861. 



The Duke of Northumberland, K.G. F.R.S. President, 

 in the Chair. 



Professor Faraday, D.C.L. F.R.S. 

 On Mr. Warren De la Rue's Photographic Eclipse Results. 



The speaker commenced by drawing attention to the sun as the great 

 source of light and heat to the planets of our system ; and to the phe- 

 nomena which occur from time to time when the earth and the moon 

 are brought by their orbital revolutions nearly or absolutely in the 

 same plane. The sun, casting shadows of the moon and of the earth 

 in an opposite direction to their illumined sides, there would always be 

 produced a total eclipse of the sun, or the moon, when these bodies 

 were situated in the same line on the same side of the sun, if the dis- 

 tances of the earth or moon invariably admitted of the one falling 

 within the shadow of the other. In consequence, however, of the 

 elliptical form of the orbits of the earth and moon, the distances of 

 these planets from each other and the sun are constantly varying, and 

 sometimes the shadow of the earth does not reach the moon, or that of 

 the moon does not reach the earth. We might consequently have, in 

 the case of the sun, either a partial eclipse when the sun, moon, and 

 earth were not exactly in the same plane, or an annular or a total 

 eclipse when they were so situated. A total eclipse might be only just 

 total, or be of a shorter or longer duration as the apparent diameter 

 of the moon exceeded by little or much the apparent diameter of the 

 sun ; no eclipse of the sun is so great, however, as to shut off the light 

 of the sun from the whole hemisphere of the earth ; on the contrary, 

 the shadow of the moon can never cover more than a very small 

 extent of the earth's surface. On the 18th of July of last year, it 



