3i'4 Intelligence and Miscellaneous Articles. 



always marks the same indestructible locality (which is entirely un- 

 affected by any subsequent motion of the body which emitted the 

 wave). In this sense it may be said to be theoretically true that the 

 locus or origin of any disturbance in a medium is for ever denned 

 in that medium. 



If we imagine a boat sailing in a smooth lake, and drop periodi- 

 cally stones into the water, circular waves will spread each time 

 from the centre of disturbance, and the degree of excentricity of 

 these waves to the moving boat (or to each other) will mark geome- 

 trically the direction and velocity of the boat's motion. So the 

 degree of excentricity of the waves about the moving sun (set up by 

 the disturbing impulses of its molecules) marks geometrically the 

 direction and velocity of the sun's proper motion. 



The following point in connexion with this subject may perhaps 

 be worth a passing notice. It has been computed (according to an 

 estimate of Sir William Thomson, based on the observations of 

 Herschel and Pouillet), that the energy of the waves given off by 

 the sun amounts (in round numbers) to 7000 horse-power per 

 square foot of surface; or, otherwise, about 1700 foot-tons of energy 

 are thrown off per second from every square foot of the sun's sur- 

 face into the aether of space. It would seem incredible (whatever 

 the constitution of the aether might be imagined to be) that all this 

 energy could be given off to a material medium in a particular direc- 

 tion (i. e. in a direction from the sun) without any reaction in the 

 opposite direction : or would it be supposed that, if the sun were 

 emitting all this energy from one side only, there would be no reac- 

 tion in the opposite direction ? Admitting that there would be a 

 certain reaction in this assumed case, then it would be reasonable 

 to conclude that, as the case actually stands, the reaction would 

 not be perfectly balanced, owing to accidental irregularities in the 

 distribution of the differently radiating materials of the sun's sur- 

 face. If this be admitted as possible, then we should have in the 

 unbalanced reaction a true physical cause for producing (or influ- 

 encing) the proper motion of the sun. 



London, October, 1878. 



ON THE DISSOCIATION OF THE OXIDES OF THE PLATINUM GROUP. 

 BY H. SAINTE-CLAIRE DEVILLE AND H. DEBRAY. 



Platinum is distinguished from all the metals with which it 

 is associated in its ores by the fact that it does not combine 

 directly w 7 ith oxygen, in whatever position we place the two bodies. 



With rhodium, palladium, and iridium the case is different. 

 When heated in a muffle, if the temperature is not too high, these 

 metals combine with oxygen : but their oxides are decomposed when 

 we raise the temperature sufficiently. 



Osmium and ruthenium combine directly with oxygen. The 

 product of this oxidation is volatile, and is formed at the highest 

 temperatures. 



