40 On the Phcenomena of Electricity . 



and is not the action of light on the photometer a proof of the 

 same kind ? My friend Cape! Lofft, Esi.j. judiciously remarks, in 

 his correspondence with me, If lit;ht were not material, but the 

 undulation of an elastic medium, then the smallest aperiure ad- 

 mitting light into a darkened room, should illuminate the whole 

 apartment equal vvith the greatest, as a spark ignites any quan- 

 tity of gunpowder however long the train. That electrical phee- 

 nomena are produced by a material agent, appears beyond a 

 question, from the exhibition of its effects on our sense'. If the 

 taste is operated upon, it is singularly affected. A snapping noise 

 and loud explosion are communicated to the ear. Light and 

 colours, and its effects on masses of matter are the circumstances 

 embraced by the or /i of vis -on ; — om feetims ]?. sensible of its 

 power. In the spark drawn from an insulated conductor, the 

 aura electrica from acuminated rods, and the shock from ac- 

 cunuilated electricity ; and it is impossible to mistake its pe- 

 culiar odour. Theie is an experiment which, I think, confirms 

 this statement ; connect the external coatings of two jars, and by 

 forming a communication between the inside linings, a charge 

 may be transferred at a single contact from a jar charged in the 

 usual way to another, and the density in each will be as the 

 ratio of the capacity. Those substances which become pho- 

 sphorescent by solar light, are precisely those which are similarly 

 illuminated hy electricity ; for this assurance, I am indebted to 

 the polite communication of Mr. Skrimshire, of Wisbeach : an 

 opportunity of repeating his experiments has not occurred to 

 nie. The circle of prismatic rings, afforded by the electric dis- 

 charge directed against a polished metallic plate from a point ; 

 and the concentric coloured zones exhibited by decomposing 

 electric light, by means of the prism, are appearances allied to 

 the supposition of the identity. A view of their corresponding 

 chemical effects will come in hereafter. 



Light moves with a velocity which is truly great, reaching the 

 orb inhabited by us, a distance from the sun of 95 millions of 

 miles, in less than eight minutes of time. The velocity of the 

 agency of electricity harmonizes with that of light. The vast 

 circuit traversed bv it in the experiments of Dr. Watson, was 

 'performed quick as the lapse of thought. Caloric is, on the 

 contrary, slow in its movement, and silver, the best conductor 

 aniv^ng the metals, proves its tardy progress, and sound itself in 

 its propagation by the elastic shells of air percurs space, only at 

 the rate of 1142 feet in a second of time. 



Light is sent off from the sun's disc in right lines, the 

 boundaries of shrdovvs and its phaencmenon when intercepted, 

 evidence this. The parallelism of solar and electric light is a 

 striking circumstance of their analogy. 



If 



