80 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XVI.) 
from the following summary ; in which metals, plumbago, sulphurets and oxides, all 
being conductors even of a thermo current, were thus combined in various ways : 
1. Platinum. 
2. Iron. 
3. Zinc. 
4. Copper. 
5. Plumbago. 
6. Scale oxide of iron. 
7. Native peroxide of manganese. 
8. Native gray sulphuret of copper. 
9. Native iron pyrites. 
10. Native copper pyrites. 
11. Galena. 
12. Artificial sulphuret of copper. 
13. Artificial sulphuret of iron. 
14. Artificial sulphuret of bismuth. 
1 and 2 with 5, 6, 7> 8, 9, 10, 11, 12, 13, 14, in turn. 
1 and 3 with 5, 6, 7 , 8, 9, 10, 11, 12, 13, 14. 
1 and 5 with 6, 7 , 8, 9, 10, 11, 12, 13, 14. 
3 and 6 with 7 , 8, 9, 10, 11, 12, 13, 14. 
4 and 5 with 6, 7 , 8, 9, 10, 11, 12, 13, 14. 
4 and 6 with 7? 8, 9, 10, 11, 12, 13, 14. 
4 and 7 with 8, 9, 10, 11, 12, 13, 14. 
4 and 8 with 9, 10, 11, 12, 13, 14. 
4 and 9 with 10, 11, 12, 13, 14. 
4 and 10 with 11, 12, 13, 14. 
4 and 11 with 12, 13, 14. 
4 and 12 with 13, 14. 
4 and 13 with 14. 
1 and 4 with 12. 
1868. Marianini states from experiment that copper is positive to sulphuret of 
copper*: with the Voltaists, according to the same philosopher, sulphuret of copper 
is positive to iron (1878.), 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. 
1869. As peroxide of lead is a body causing a powerful current in solution of sul- 
phuret 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 
(1822.), was therefore well dried, which is quite essential in these cases, and formed 
into the following combinations : 
Platinum. Zinc. Peroxide of lead. 
Platinum. Lead. Peroxide of lead. 
Platinum. Cadmium. Peroxide of lead. 
Platinum. Iron. Peroxide of lead. 
* Memoria della Society Italiana in Modena, 1827, xxi. 224. 
