VOL. LX.] PHILOSOPHICAL TRANSACTIONS. SQ 



^ of an inch from another rod, which was likewise insulated, and one end of 

 which was in contact with the coating of the jar; and having electrified the rod 

 that supported the pith balls, and placed a rod loaded with the same electricity 

 near them : he observed that on every discharge, the balls, which before were 

 repelled, were instantly attracted by the electrical rod; and that the result was 

 invariably the same, whether they and the rod were loaded with positive or ne- 

 gative electricity: and also whether the jar was charged positively or negatively. 

 He repeated the experiment for several hours, without the least variation in the 

 event: which clearly proved, that in these circumstances the electricity of the rod 

 that received the lateral explosion was discharged by it. 



Afterwards, Dr. P. repeated this experiment with some little variety, and found 

 the electricity of the rod only lessened by the lateral explosion. These experi- 

 ments however by no means favoured the supposition of the uniform communi- 

 cation of electricity, either that of the inside or that of the outside of the jar : 

 and together with the former experiments, convinced him that this lateral spark 

 by no means produced the effect that might have been expected in communi- 

 cating electricity. But with the next set of experiments, the difficulty began a 

 little to clear up, and continued to do so gradually, till he gained all the satisfac- 

 tion he could wish for, with respect to this puzzling phenomenon. The first 

 time that he was able to vary the electricity of the insulated body placed near the 

 electric circuit, or of the bodies that formed the circuit (which he now began 

 to attend to), by any different adjustment of the apparatus, was on the following 

 occasion. 



Near to an iron rod, that touched the bottom of a jar charged positively, he 

 placed another insulated rod, with a pair of pith balls hanging to it ; and ob- 

 served, that when he attempted to make the discharge through an imperfectly 

 conducting circuit, (bringing for instance, part of the table into it), a strong 

 spark passed between the insulated rod and the other that touched the jar, and 

 immediately the balls separated as far as they possibly could ; and, continuing in 

 a repulsive state, appeared to be electrified negatively. But immediately com- 

 pleting the circuit with good conductors, and making the remainder of the ex- 

 plosion in a full spark ; another spark passed between the two rods, and imme- 

 diately the balls fell close together again ; and sometimes would separate with the 

 opposite, or positive, electricity. 



Dr. P. could not, on this occasion, make the lateral spark, in the full explo- 

 sion, so great as in the imperfect discharge. He also observed, that the more 

 interrupted the circuit was, the farther would the lateral explosion reach ; and 

 that the electricity, which the full explosion communicated, was always positive 

 when the jar was charged positively, and negative when it was charged nega- 

 tively. The result of the imperfect discharge was always the reverse. Insulating 



