1503. If a quantity of mercury in a dry glass be con-
nected, by a wire, with a gold leaf electroscope, and a dry
rod of glass be immersed in it, what is observed if it be left
there, and also when the rod is gradually withdrawn ? (M.)

1504. Name some substances that seem incapable of re-
ceiving electric excitement by friction.
1505. I wish you to show me a few simple electrical
effects; how will you do it ? (T.)

1506. If, upon a warm board, a dry sheet of paper be rub-
bed with india-rubber, it is electrified. How is this proved ?

(T.)

1507. Can electric phenomena be produced in vacuoy or in
an atmosphere of carbonic acid gas ?

1508. Show by a simple experiment that the electncity
developed on resin by the friction of flannel is different from
that developed on glass by the friction of silk. (T.)

1509. I wish you to prove that like electricities repel each
other, and that unlike electricities attract each other.
162 QUXmOHB AMD VROVLMMB IV FHTSIOS.
