ON PRACTICAL STANDARDS FOR ELECTRICAL MEASUREMENTS. 75 
October 1907. With a view to a preliminary agreement on the matters 
to be raised, correspondence has passed during the year between the 
Secretary, acting as Director of the National Physical Laboratory, and 
the heads of standardising laboratories in other countries. The Con- 
ference will probably deal with the drawing up of an International 
Convention relative to Electric Units, which should include the draft of 
a form of law which might be adopted generally in the various countries 
represented, and the consideration of the steps necessary to secure 
uniformity in the carrying out of the laws in different countries, and to 
arrange for determinations necessary for this purpose. 
The necessary invitations for the Conference are being issued by his 
Majesty’s Government. 
To secure uniformity in carrying out the law it will be necessary that 
specifications for constructing and using a mercury unit of resistance, for 
setting up and working a silver voltameter, and for preparing a standard 
cell, be approved either by the Conference itself or by some body 
nominated by the Conference for this purpose. 
With a view to aiding discussion, very detailed specifications dealing 
with the voltameter and the cell have been prepared by the National 
Physical Laboratory and issued to other standardising institutions. 
These are printed in Appendices II. and III. 
lt is not suggested that the final specifications need be so full or so 
detailed, but it was thought well that all information necessary to assist 
in criticising the results should be included. 
The work on the silver voltameter and Weston cell still continues 
and, in view of the deliberations of the Conference, it is probable that 
further expenditure will be required. The accounts show that a balance 
of 10s. 8d. remains from the grant of 50/. made last year. The grant 
has been spent on the purchase of material and appliances for the 
research. 
In view of the importance of bringing the work of re-determining the 
values of the fundamental units to a satisfactory conclusion, the Com- 
mittee recommend that they be reappointed, with a grant of 50/., and 
with the addition of the names of Mr. A. P. Trotter, Mr. T. Mather, 
F.R.S., and Mr. F. E. Smith; that Lord Rayleigh be Chairman and 
Dr. Glazebrook Secretary. 
APPENDIX I. 
Notes on the Present Condition of the Work on Electric Units at the 
National Physical Laboratory. By F. E. Surra. 
(From the National Physical Laboratory.) 
1. The Ohm.—(a) Absolute Unit.—The value of a resistance in absolute 
measure is still subject to considerable uncertainty ; the most satisfactory 
value is obtained from the mean observed ratio of the International Ohm 
to the absolute ohm.! 
A provisional design has been prepared for the Lorenz apparatus 
which the Drapers’ Company are kindly presenting to the National 
Physical Laboratory, and experiments to test the more important features 
‘ See table in the Brit. Assoc. Rep. for 1892. 
