ELECTRICITY. 



Ill 



the better of her discretion, and she took a third shock, which immediately ' 

 produced bleeding at the nose. 



No sooner were these experiments made known, than the amazement of ' 

 all classes of people of every age, sex, and rank, was excited at what was re- \ 

 gardcd as " a prodigy of nature and philosophy." Philosophers everywhere ' 



( repeated the experiment, but none succeeded in explaining its effects. After ! 



I the first emotions of astonishment had abated, the circumstances which influ- 



< enced the force of the shock were examined. Muschenbroek observed that 

 if the glass were wet on the outer surface the success of the experiment was 

 impaired ; and Dr. Watson proved that the force of the shock was increased 

 by the thinness of the glass of which the bottle containing the water was made. 

 He also observed, that the force of the charge did not depend on the power of 

 the electrical machine by which the phial was charged. Dr. Watson also 

 showed that the shock could be transmitted, undiminished, through the bodies 

 of several men touching each other. 



By further repeating and varying the experiment, Watson found that the force 

 of the charge depended on the extent of the external surface of the glass in 

 contact with the hand of the operator ; and it occurred to Dr. Bevis that the 

 hand might be efficient merely as a conductor of electricity, and in that case 

 the object might be more effectually and conveniently attained by coating the 

 exterior of the phial with sheet-lead or tin-foil. This expedient was completely 

 successful ; and the phial, so far as related to its external surface, assumed its 

 present form. 



Another important step in the improvement of the Leyden jar was also due 

 to the suggestion of Dr. Bevis. It appeared that the force of the charge in- 

 creased with the magnitude of the jar, but not in proportion to the quantity of 

 water it contained. It was conjectured that it might depend on the extent of 

 the surface of glass in contact with water ; and that as water was considered 

 to play the part merely of a conductor in the experiment, metal, which was a 

 better conductor, would be at least equally effectual. Three phials were there- 

 fore procured and filled to the usual height with shot instead of water. A me- 

 tallic communication was made between the shot contained in them respectively. 

 The result was a charge of greatly augmented force. This was, in fact, the 

 first electric battery. 



Dr. Bevis now saw that the seat of the electric influence was the surface of 

 contact of the metal and the glass, and rightly inferred that the form of a bot- 

 tle or jar was not in any way connected with the principle of the experiment. 

 He therefore took a common pane of glass, and having coated the opposite 

 faces with tin-foil, extending on each surface within about an inch of the edge, 

 he was able to obtain as strong a charge as from a phial having the same ex- 

 tent of coated surface. Dr. Watson being informed of this, coated large jars 

 made of thin glass both on the inside and outside surface with silver leaf, ex- 

 tending nearly to the top of the jars, the effects of which fully corroborated 

 the anticipations of Dr. Bevis, and established the principle that the force of 

 the charge was in proportion to the quantity of coated surface. 



The results of all these experiments led to the inference that, in the dis- 

 charge of the phial, the electricity passed through the circle of conducting 

 matter which was extended between the inside and the outside coating of the 

 jar. If that circle were anywhere interrupted by the presence of non-conduct- 

 ing matter, or electrics per se, as they were then called, no discharge took place. 

 Also, if any portion of the circle were formed of living animals, each 

 animal sustained the shock. To carry the demonstration of this further, 

 Dr. Watson placed, at several points in the circuit, spoons filled with spirits 



\ between the extremities of iron bars, but not in contact with them. In such 



