156 REPORT—1862. 
each other, and with a third one copied by my friend Dr. Teddersen, at 
Leipzig, from the original of M. Leyser, which I took therefore to be the 
more correct ones. I found the absolute value of Siemens’s unit to be 
603 ow 
660° 10° 
or 1:1 Siemens’s unit=10"°. 
We should therefore only have to multiply all observations expressed in 
10 
Siemens’s units by a to reduce them to absolute measure, and the suggested 
multiple for the future standard would not be far from 1:1 of Siemens’s units, 
which every one admits to be for metallic conductors a practical unit. 
For the resistance of insulating materials the figures become impracticably 
high; but it would be a matter of professional telegraphy to adopt, in con- 
formity with the system, the ‘resistance’ 10’° and, besides, another ‘ great 
resistance’ containing 10’° ‘ resistances.’ 
While the resistance of a mile of copper in an ordinary cable would be (say) 
4 R. (four resistances), the insulation-resistance of a mile of cable would be 
about 0:04 G. R. (great or gutta-percha resistances), 
My suggestion would therefore be— 
1. To adopt Weber’s absolute unit, and to derive from it, by the multiple 
10” (or 10,000,000,000), the practical unit. 
2. To adopt 10° of Weber’s electro-magnetic units as the ‘ say abso- 
lute unit’ for electromotive force and resistance. 
(10 of these units would be exactly 1 Daniell’s cell.) 
3. 1 of these units would be 1-1 of Siemens’s units. 
4. To allow, besides, a ‘ practical great unit,’ viz. 10'° of the ‘practical 
units,’ for resistances in order to express the insulation-resistance of cables 
in convenient figures. 
1 
5. To allow also a ‘ practical small unit’ of io” absolute units to express 
insulation-currents and charge-quantities of cables in convenient figures. 
6. To adopt, in order to avoid confusion, for such ‘practical units’ a 
terminology as proposed by Messrs. Bright and Clark. 
London, September 18, 1862. 
Arvpenpix G.—Circular addressed to Foreign Men of Science. 
Srr,—I am requested to inform you that a Committee was appointed by the 
British Association, which met last year at Manchester, to report on Electrical 
Standards of Resistance. 
The Committee consists of the following gentlemen :— 
Professor A. W. Williamson, F.R.S. | Professor W. H. Miller, F.R.S. ne 
(University College, London). bridge). 
Professor Charles Wheatstone, F.R.S. | A. Matthiessen, Ph.D., F.R.S. (Lon- 
(London). don). 
Professor William Thomson, F.R.S. | Fleeming Jenkin, Esq. (London). 
(Glasgow). 
The Committee met on December 6th, 1861, and on April 3rd, 1862. On 
the latter occasion the following Resolution was passed :— 
* Resolved,—That the following gentlemen be informed of the appoint- 
ment of the present Committee, and be requested to furnish suggestions 
in furtherance of its object. 
