250 0. N. Rood—Nature and Duration of 
ee = a spark. it is tet as I shall show, to 
adjust either the cloct#ioat surface of the jar, or its striking dis- 
tance, so that with a given coil only a single st will be pro- 
a 
Much of the apparatus employed was that already described, 
but it may not be amiss to “ak here some details reper it, 
sen cups, arranged for meet and the length of the simple 
was less —_ 7xbg0 Of a second. These experiments, he states, were Be 
ay fe eee ving 800 — in a second, with exactly the same 
At the time I wrote my paper I was perfectly well nap that pn 
tioned in the same paper that he had obtained of ae 
taking place alf an ile of copper one, a duration of zrb0g : 
second. This I take to be an y different matter intrinsically, an andit 
also from my own experiments, e the circuit was as short ble, 
is easy corres’ opinion was ente: of 8 
