394! M. BufF o?i the Laiv of Electrolytic Conduction. 



If all these luminous meteors are produced, as some of them 

 certaiuly have been, by the combustion of those solid masses of 

 metal and stone which occasionally strike upon the earth, we 

 might possibly learn the composition of a particular meteor by 

 the colour it displays. But this is a very complicated problem. 

 We know of what substances meteorites usually consist; but 

 each one contains several elements which may all glow together, 

 and may burn either together or separately. Iron is a consti- 

 tuent seldom wanting; and this metal, when heated, exhibits 

 first what is called " dull redness," but which consists princi- 

 pally of orange and even green rays ; as the heat increases, it 

 becomes " bright red," and then emits true red rays in large 

 quantity : when it catches fire in the air it scintillates, giving 

 forth blue rays in addition to those already mentioned, and ap- 

 pearing of a reddish-white colour. It can scarcely be doubted 

 that many of the red and white-red meteors, especially those that 

 throw off red sparks, consist of this metal. If iron, whether 

 meteoric or otherwise, be ignited in the broken galvanic circuit, 

 the electric light is superadded to that of the burning metal, 

 producing an intensely luminous flame which appears white, 

 but casts a bluish radiance on surrounding objects. Nickel 

 when ignited displays a somewhat larger amount of green rays. 

 Meteoric iron always contains more or less sulphur and phos- 

 phorus : the last of these elements in burning emits all the rays 

 of the solar spectrum : the blue colour of burning sulphur is 

 well known ; yet it differs greatly according to the intensity of 

 the combustion. If iron pyrites be set on fire in air, the flames 

 of both elements become distinctly visible, and the sulphur will 

 continue to burn after the iron has ceased to do so. The cobalt, 

 zinc, lead, and other metals occasionally found in meteorites 

 will of course burn with their distinct flames; and the silicate of 

 magnesia or other minerals are capable of becoming brilliantly 

 incandescent. 



LXIII. On the Law of Electrolytic Conduction. 5y M. Buff. 

 In a Letter to Mr. Faraday*. 



My dear Sir, 



A FEW years ago you raised some doubts as to the generality 

 of the law, that in compound fluids there is no conduction 

 without decomjjosition. These doubts referred to our imperfect 

 acquaintance with the deportment of the more complicated com- 

 pounds, and to the property possessed by several electrolytes to 

 conduct electricity when in the solid condition. 



* Communicated by Professor Faraday. 



