VOL. XLI.] PHILOSOPHICAL TRANSACTIONS. 30g 



little distance, the two threads immediately receded from each other consi- 

 derably at the bottom. He then removed one of the threads, and held the 

 tube over the other, in the same manner as before. The single thread was not 

 observed to move to either side ; consequently the moving of the threads side- 

 ways was occasioned neither by the attraction of the cross line, nor that of the 

 tube, nor by the frame of wood, to which the cross line was tied at each end, 

 but only by their action on each other. 



He then added a third string, at the same distance from the second, that the 

 second was from the first, and on holding the excited tube over the middle one, 

 at tlie same distance from the cross silk, as before, when the strings continued 

 in the same plane, the middle one stood still, and the string on each side of it 

 receded considerably at the bottom part, which in this case must necessarily 

 happen, on a supposition that they repel each other equally ; for the two con- 

 trary forces of the outer threads destroy each other, and consequently the 

 middle one must remain quiet ; but there was nothing to hinder the middle one 

 from repelling the two outer on each hand sideways. When, as it often hap- 

 pened, the three pendulous threads did not remain in the same plane, they 

 then all receded from one another equally, and formed nearly a triangular 

 prism ; the three threads being the three edges, or rather a triangular pyramid 

 with the top cut oft". 



On suspending 4 threads at the same distance as before from one another ; if 

 they continued in the same plane, they all parted, but the two outermost 

 more from their neighbours, than the two in the middle from each other. If 

 they moved out of the plane they were first in, they formed two prisms, each 

 extreme with the two in the middle forming one, or rather a parallelopepid, less 

 at top than at bottom. 



When 5 strings were suspended, either the middlemost continued sta- 

 tionary when the plane was not altered, or if it was, they formed 3 prisms. 



Exper. 1. Mr. W. afterwards placed two cross blue silks, of the same length 

 as before ; about half an inch asunder from one another horizontally, and tied 

 at each end ; and on each of these, at different times, hung 2, 3, 4, and 5 

 threads, at the same distances as before, when every thing succeeded, as it 

 ought to have done, on a supposition of their mutually repelling one an- 

 other. 



Exper. 3. To each of the ends of two threads, suspended as at first, a fea- 

 ther being tied, the two feathers manifestly receded from each other ; and when 

 3 threads had each a feather at their extremities, the middlemost became sta- 

 tionary, and the two outer went off on each hand.- 



