1412.  Amongst other results, I expected and sought for the mutual affection, or even the lateral coalition of two similar sparks, if they could be obtained simultaneously side by side, and sufficiently near to each other.  For this purpose, two similar Leyden jars were supplied with rods of copper projecting from their balls in a horizontal direction, the rods being about 0.2 of an inch thick, and rounded at the ends.  The jars were placed upon a sheet of tinfoil, and so adjusted that their rods, a and b, were near together, in the position represented in plan at fig. 116:  c and d were two brass balls connected by a brass rod and insulated:  e was also a brass ball connected, by a wire, with the ground and with the tinfoil upon which the Leyden jars were placed.  By laying an insulated metal rod across from a to b, charging the jars, and removing the rod, both the jars could be brought up to the same intensity of charge (1370.).  Then, making the ball e approach the ball d, at the moment the spark passed there, two sparks passed between the rods n, o, and the ball c; and as far as the eye could judge, or the conditions determine, they were simultaneous.

1413.  Under these circumstances two modes of discharge took place; either each end had its own particular spark to the ball, or else one end only was associated by a spark with the ball, but was at the same time related to the other end by a spark between the two.

1414.  When the ball c was about an inch in diameter, the ends n and o, about half an inch from it, and about 0.4 of an inch from each other, the two sparks to the ball could be obtained.  When for the purpose of bringing the sparks nearer together, the ends, n and o, were brought closer to each other, then, unless very carefully adjusted, only one end had a spark with the ball, the other having a spark to it; and the least variation of position would cause either n or o to be the end which, giving the direct spark to the ball, was also the one through, or by means of which, the other discharged its electricity.

1415.  On making the ball c smaller, I found that then it was needful to make the interval between the ends n and o larger in proportion to the distance between them and the ball c.  On making c larger, I found I could diminish the interval, and so bring the two simultaneous separate sparks closer together, until, at last, the distance between them was not more at the widest part than 0.6 of their whole length.

1416.  Numerous sparks were then passed and carefully observed.  They were very rarely straight, but either curved or bent irregularly.  In the average of cases they were, I think, decidedly convex towards each other; perhaps two-thirds presented more or less of this effect, the rest bulging more or less outwards.  I was never able, however, to obtain sparks which, separately leaving the ends of the wires n and o, conjoined into one spark before they reached or communicated with the ball c.  At present, therefore, though I think I saw a tendency in the sparks to unite, I cannot assert it as a fact.