256 Faraday's Researches

1. Platinum.

2. Iron.

3. Zinc.

4. Copper.

5. Plumbago.

6. Scale oxide of iron.

7. Native peroxide of manganese.

8. Native grey sulphuret of copper.

9. Native iron pyrites.
10. Native copper pyrites,
n. Galena.

12. Artificial sulphuret of copper.

13. Artificial sulphuret of iron.

14. Artificial sulphuret of bismuth.

i and 2 with 5, 6, 7, 8, 9, io; n, 12, 13, 14, in turn,
i and 3 with 5, 6, 7, 8, 9, 10, n, 12, 13, 14.
i and 5 with 6, 7, 8, 9, 10, n, 12, 13, 14.

3 and 6 with 7, 8, 9, 10, n, 12, 13, 14.

4 and 5 with 6, 7, 8, 9, 10, n, 12, 13, 14.
4 and 6 with 7, 8, 9, 10, n, 12, 13, 14.

4 and 7 with 8, 9, 10, n, 12, 13, 14.
4 and 8 with 9, 10, u, 12^ 13, 14.
4 and 9 with io; n, 12., 13, 14.
4 and 10 with n, 12,, 13, 14.
4 and 11 with 12, 13, 14.
4 and 12 with 13, 14.
4 and 13 with 14.
i and 4 with 12.

856. Marianini states from experiment that copper is positive
to sulphuret of copper;l with the Voltaists, according to the
same philosopher, sulphuret of copper is positive to iron (866),
and with them also iron is positive to copper. These three
bodies therefore ought to give a most powerful circle: but on
the contrary, whatever sulphuret of copper I have used, I have
found not the slightest effect from such an arrangement.

857. As peroxide of lead is a body causing a powerful current
in solution of sulphuret of potassium, and indeed in every case
of a circuit where it can give up part of its oxygen, I thought
it reasonable to expect that its contact with metals would
produce a current, if contact ever could. A part of that which
had been prepared (810), was therefore well dried, which is

1 Mcmorie della Society Italiana in Modena, 1827, xxi. 224.rce to the cases where nitrous acid, nitric