74 REPORTS ON THE STATE OF SCIENCE. 
Of the 71 observations made 
7 are within 1 in a million of the mean 
14 ” ” 2 ” ” ” ” 
28 ” ” 5 ” ” ” ” 
53 ” ” 10 ” ” ” ” 
66 9 ” 15 ” ” ” ” 
70 9 ” 20 ” ” ” ” 
Only one determination out of the whole 71, and this one of the earliest, 
differs from the mean by so much as | part in 59,000. 
The above facts constitute important evidence of constancy in both 
balance and cel]. In fact, both current-weigher and cell proved to be 
much more constant and reliable than the standard resistance, although 
the latter was very carefully made and annealed with a view to ensuring 
permanency. 
Expressed in terms of the international ohm as realised at the 
National Physical Laboratory, and of the ampere as given by the new 
current-weigher, we find that the value of C x R for the normal Weston 
cadmium cell is 1:01830, at 17° C. 
This assumes that the value of g at-Teddington is 981:19, a number 
probably correct to within 3 part in 100,000. An uncertainty of this 
amount in g introduces a possible error of 15 part in 100,000 in the 
value of the ampere, and, as all other probable errors are smaller in 
magnitude, it is important that a more accurate determination of g be 
made. 
To realise the volt with an accuracy approaching that of the ampere, 
as now known, it is necessary that an absolute determination of resistance 
of corresponding precision be undertaken. Through the kindness of the 
Drapers’ Company of London it is hoped that such a determination by 
means of a Lorenz apparatus maybe completed at. the National Physical 
Laboratory before the end of next year. At the present time thie 
uncertainty in the absolute value of the international ohm approximates ~ 
to 4 in 10,000. 
From the above value of C xR for the cadmium cell, together with 
the ratio of Clark to cadmium, viz., 
Clark at 15° C. 
Cadmium at 17° C. ~~ L408 6 
the e.m.f. of the Clark cell at 15° C. becomes 1°432,. 
The Committee recognise very fully the skill and devotion of Mr. 
Mather and Mr. Smith, on whom the work of carrying out the experi- 
ments has fallen, and have invited these gentlemen to become members 
of the Coramittee. 
Papers by Mr. F. E. Smith, of the National Physical Laboratory, 
dealing with the use of the silver voltameter and the preparation of the 
Weston cadmium cell, are nearly ready for publication. 
Some preliminary work has also been done on the design for the 
Lorenz apparatus, the funds for which are being found by the Drapers’ 
Company. The proposed design embodies new features of importance. 
With regard to the proposed Conference on Electric Units, further 
consideration led to the conclusion that a year’s delay was desirable, 
and in consequence the meeting was postponed from October 1906 to 
