British Association 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 ora 
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 
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 mae for a considerable time.—Prof. Stevelly 
wished to hat had fallen from Prof. Lloyd and M. de la 
Rive by stating am whenever the Scotch hills appeared with 
peculiar vividness and distinctness, from the Lough of Belfast, the 
fishermen always looked “upon itasa sure precursor of heavy rain 
had noticed this appearance while standing on the beach at Holly- 
wood, and pointed it out to an old fisherman ; the old man imme- 
diately gave notice to all his friends to atic he had access, who 
