1 ON STANDARDS FOR USE IN ELECTRICAL MEASUREMENTS. 125 
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SP RS 
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an air-pump, which was connected with a water-pump; this was left 
running for two or three hours till all air-bubbles had disappeared ; the 
weight of the wire in water was determined, and a second reading taken 
some hours later. As the weight of wire used was from 16 to 20 grammes, 
fairly accurate values for the specific gravity of the several wires were ob- 
tained, and thus the value for each wire in terms of the B.A. unit for the 
resistance to conduction between the opposite faces of a cube of the material 
was found. 
Resistance of Various Specimens of Wire. 
Resistance of a wire 
such that 1 metre Specific resistance per 
4 weighs 1 gramme Specific ee. at 18° C. in 
Wire Date at 18° C. in B.A. units | gravity B.A. units x 10-9 
Hard-drawn| Annealed Hard-drawn, Annealed 
I. | July 22, 1889 — 1549 8°86 _— 1743 
Noy. 6, 1889 — 1550 8°87 — 1745 
II. | July 22, 1889 — 1545 8°88 — 1741 
Dec. 2, 1889 = 1546 8°89 —_ 1742 
Ill. | Dec. 3, 1889 —_ 1713 8°87 — 1922 
IV. | July 10, 1889 1578 — 8°89 1776 ss 
Aug. 1, 1889 1578 — 8°89 1776 — 
IV.’ | Nov. 1, 1889 — 1511 8°885 — 1724 
V. | July 31, 1889 1573 — 8°89 1770 ue 
Oct. 30, 1889 1572 — 8:89 1770 = 
V.' | July 20, 1889 — 1526 8:89 — 1712 
Aug. 2, 1889 — 1526 8°89 = 1713 
Aug. 8, 1889 — 1527 8°89 _— 1716 
VI. | Aug. 10, 1889 1546 — 8°94 1730 = 
Oct. 18, 1889 1549 -- 8-94 1732 — 
July 10,1890] 1549 bs 8-94 1731 ie 
July 14, 1890 1548 — not obsrvd. xb pide 
VI’ | Aug. 8, 1889 _ 1508 8°94 _ 1688 
Oct. 11, 1889 _ 1509 8:94 —_ 1688 
VII. | Nov. 4, 1889 1543 — 8946 1724 — 
July 15, 1890 1543 = =a “5 = 
VIII. Oct. 23, 1889 1700 _— 8°95 1903 - 
Oct. 28, 1889 1702 — —- — as 
IX. Aug. 5, 1890 1572 — 8:90 1766 — 
Aug. 18, 1890 1572 —_ 8-90 1766 —_— 
X. Aug. 5, 1890 1573 —_ 8-91 1767 —_— 
Aug. 26, 1890 1569 _ 8°92 1751 _ 
XI. | Aug. 27,1890] 1569 = 8-93 1750 MA 
As calcu- 
| Matthiessen’s value re- Hsin 
duced to 18°, using 1571 _— not given| 17666 Plat cged e 
his own coefficient Tht: vis 
itz- 
patrick 
re en, 
The first object of these experiments was to test directly in com- 
parison with the B.A. standards samples of copper wire of high con- 
