124 REPORT—1863. 
2nd. Immediately on the conclusion of these experiments, equal standards, 
constructed of such metals as promise the greatest constancy, will be depo- 
sited at Kew, where the permanence of their equality will be ngorously tested. 
3rd. Unit resistance-coils of the best known construction will be issued to 
the public. 
4th. The experiments already begun on the permanence of the electrical 
resistance of wires and alloys under various circumstances will be continued 
and extended. 
5th. The experiments on the reproduction of standards by chemical means 
will be continued. 
6th. Experiments on the best construction of gauges of electromotive force 
or difference of potential, and on electrometers, will be continued. 
7th. A standard galvanometer, for the measurement of currents in absolute 
measure, will be constructed, and electro-dynamometers for the same purpose 
compared with the standard instrument, and issued to the public. 
8th. Experiments on the ratio between the electrostatic units and the 
electromagnetic units will be undertaken. 
9th. Experiments will be made on the development of heat in conductors 
of known absolute resistance with currents of known absolute magnitude, 
The results of this experiment will give, by equation (3), a new and very 
accurate determination of the mechanical value of the unit of heat. 
The conclusion of the experiments on absolute resistance, and the adoption 
of the absolute system as the basis of all electrical measurement, will, it is 
hoped, allow considerable progress to be made in most of these researches, 
Apprenprx A.—On the Electrical Permanency of Metals and Alloys. 
By A. Marrutessen, F.R.S, 
Tur following are the results obtained with the metals and alloys described 
in Appendix B. of the Report on Standards of Electrical Resistance by your 
Committee :-— 
The wires to be experimented on were— 
Johnson and Matthey. 
1. Silver: hard drawn........ see 
2. Silver: annealed ......«..- } Caniroun ssp Soe eee 
3. Silver: hard-drawn........ Cut from the same piece, but different 
4, Silver: annealed.,......). ..+ from 1 and 2; pure. 
5. Copper: hard-drawn ...... , ‘ Pet i 
6. Copper: annealed.......... ciara tg ay igs ing : 
7. Copper: hard-drawn ...... Cut from the same piece, but different 
8. Copper: annealed.......... from 5 and 6; pure. 
lag ea ae Onktnomaele ea emma 
11. Gold: hard-drawn ........ Cut from the same piece, but different 
12. Gold: annealed .......... from 9 and 10; pure. 
13, Platinum: hard-drawn Cut from the same piece; commercial. 
14. Platinum: hard-drawn .... ‘ 
15. Gold-silver alloy: hard-drawn | Cut from same piece. Made by Messrs. 
16. Gold-silver alloy : hard-drawn e 
. Cut from the same piece. No. 19 ar- 
17. German silver: Pome a, ranged with longer connectors, and 
18, German silver: ememed 7 used as normal wire with which the 
19. German silver: annealed.... rest were compared. 
