NATURAL PHILOSOPHY. 109 



ascribed to a polar state which these substances then take), all matter 

 expands by heat. This expansion of matter, so caused, can be com- 

 municated to neighboring bodies. In the case of heat produced by 

 intense chemical action, he ascribed the effect to the physical force of 

 a species of molecular friction on the particles acted on. This chem- 

 ical force is capable of transfer by the voltaic battery, and the calorific 

 force moves with it. It has been proved, by experiment on -a com- 

 pound wire of silver and platinum, that, in proportion to the increase 

 of conducting power, ignition is diminished. Mr. Grove here re- 

 ferred to recent researches of his own, to prove that this calorific force 

 was affected by external causes. The same current was sent through 

 two coils of fine platinum wire, one of which was surrounded by an 

 atmosphere of air, the other by an atmosphere of hydrogen, when it 

 was found that the wire in air became white-hot, while that in hydro- 

 gen was not heated. This phenomenon he ascribed either to the mo- 

 bility of the particles of the hydrogen, or to the vibrations moving 

 away from the vibrating surface, or to the state of the surface itself, 

 hydrogen being, as to radiating power, to air, as the color black is to 

 white. That this cooling does not depend on rarefaction, is proved 

 by the intense heat and light produced in vacua. Mr. Grove then 

 called the attention of the Institution to a remarkable experiment lately 

 performed by him, with a battery of 500 cells ; of the two platinum 

 poles, the positive was placed under water, the negative held over it, 

 when a cone of flame issued from the surface of the water towards 

 the negative pole, on the extremity of which a small globule was 

 formed, which fell off as soon as the current was suspended. These 

 facts may serve to explain more clearly the phenomena of the voltaic 

 arc. Mr. Grove exhibited paper on which the strong disruptive effect 

 of the electric battery had dispersed metallic wires, and he showed 

 that these explosions had always occurred in a line transverse to that 

 of the current. He inferred that when ignition commenced in the 

 wire, its molecules assumed a transverse polar direction. When 

 platinum is ignited under circumstances which admit of the effects 

 being accurately noticed, it contracts, swells, and breaks, and a lead 

 wire, similarly acted on, becomes divided by a series of transverse 

 facets. In conclusion, Mr. Grove adverted to recent endeavors to 

 obtain voltaic light for practical purposes. He stated that recent cal- 

 culations led him to believe that for some purposes, such as the illu- 

 mination of light-houses, especially where an intermittent light was 

 wanted, and of the interior of large buildings, it might possibly be 

 adopted at no very remote period. The light of 1,440 candles might 

 be obtained at about four shillings per hour; but this concentrated 

 light is not applicable for streets. The whole subject, however, is 

 beset by many mechanical difficulties. London Athenaeum, March. 



THE VELOCITY OF ELECTRICAL WAVES. 



IT is well known that for the past two or three years the electric 

 telegraph has been employed for the purpose of" ascertaining the 

 longitude of various places in this country, which has thus been done 



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