16 British Association for the Advancement of Science. 



into it, by the force of the blows, Hke so many wedges, thereby 

 weakening the strength of the iron. 



Electricity. — Prof Henry then made a communication respect- 

 ing the Lateral Discharge in common Electricity. 



The primary object of these investigations was to detect, if 

 possible, an inductive action in common electricity, analogous to 

 that discovered in a current of galvanism. For this purpose an 

 analysis was instituted, of the phenomena known in ordinary 

 electricity by the name of the lateral discharge. Prof. Henry 

 was induced to commence with this from some remarks by Dr. 

 Roget on the subject. The method of studying the lateral spark 

 consisted in catching it on the knob of a small Leyden phial, and 

 presenting this to an electrometer. The result of the analyses 

 was in accordance with an opinion of Biot, that the lateral dis- 

 charge is due only to the escape of the small quantity of redun- 

 dant electricity which always exists on one or the other side of a 

 jar, and not to the whole discharge. The Professor then stated 

 several consequences which would flow from this ; namely, that 

 we could increase or diminish the lateral action, by the several 

 means which would affect the quantity of redundant, or as it 

 may be called, free electricity, such as an increase of the thick- 

 ness of the glass, or by substituting for the small knob of the jar 

 a large ball. But the arrangement which produces the greatest 

 effect, is that of a long fine copper wire insulated, parallel to the 

 horizon, and terminated at each end by a small ball. When 

 sparks are thrown on this from a globe of about a foot in diame- 

 ter, the wire, at each discharge, becomes beautifully luminous 

 from one end to the other, even if it be a hundred feet long ; rays 

 are given off on all sides perpendicular to the axis of the wire. 

 In this arrangement the electricity of the globe may be consid- 

 ered nearly all as free electricity ; and as the insulated wire con- 

 tains its natiual quantity, the whole spark is thrown off in the 

 form of a lateral discharge. But to explain this phenomenon 

 more fully, Prof Henry remarked, that it appeared necessary to 

 add an additional postulate to our theory of the principle of elec- 

 tricity, — namely, a kind of momentimi, or inertia, without weight ; 

 by this he would only be understood to express the classification 

 or generalization of a number of facts, which would otherwise 

 be insulated. To illustrate this, he stated that the same quantity 

 of electricity could be made to remain on the wire if gradually 



