British Associatioii for the Advancement of Science. 7 



very fine powder, composed of platina in the metallic state, but 

 extremely divided. The same phenomenon takes place with gold, 

 palladium, silver, &c. All these metals are covered, in the same 

 manner, with a very fine coating of the metal itself, in a state of 

 extreme subdivision. The author has assured himself that this 

 powder was composed of the metal itself, and not an oxide or a 

 suboxide. He inquired whether this effect is the result of the 

 mechanical shocks that the molecules of the metal undergo by the 

 action of these currents, which are discontinuous, and alternately 

 in opposite directions ; and whether it would not be augmented 

 by the succession of oxidations and deoxidations, which would 

 occur on the surface of the wires. He concluded by stating, that 

 he had observed that the armatures of soft iron (about which the 

 metallic wires are coiled, in which the currents are developed by 

 induction, ) cease to be attracted by the poles of the magnets, be- 

 fore which they pass when the two ends of the wire in which the 

 current is developed are united by one good metallic conductor ; 

 a fact which would seem to prove that Magnetism and Dynamical 

 Electricity are, in these cases, but two different forms of the same 

 force, one of which disappears when the other becomes apparent ; 

 and he insisted on the advantage that we might derive from this 

 property in the production of motion by electro-magnets. 



Clearness of the Air. — Prof. Lloyd said that the distinctness 

 and vividness with which distant objects were seen in some states 

 of the atmosphere was quite astonishing : on one occasion he had 

 seen from the neighborhood of Dublin the Welsh hills from their 

 very bases, and brought so near, apparently, that he could abso- 

 lutely see the larger inequalities of the surface upon the sides of 

 the mountains. That the atmosphere was at the time very much 

 loaded with vapor in a highly transparent state, was obvious from 

 the fact, that immediately after a very heavy fall of rain took 

 place, and continued for a considerable time. — Prof. Stevelly 

 wished to confirm what had fallen from Prof. Lloyd and M. de la 

 Rive by stating that whenever the Scotch hills appeared with 

 peculiar vividness and distinctness, from the Lough of Belfast, the 

 fishermen always looked upon it as a sure precursor of heavy rain 

 and wind. A friend had informed him that on one occasion he 

 had noticed this appearance while standing on the beach at Holly- 

 wood, and pointed it out to an old fisheraian ,• the old man imme- 

 diately gave notice to all his friends to whom he had access, who 



