ON STANDARDS’ OF ELECTRICAL RESISTANCE, 131 
determinations and the material standard should from time to time be ob- 
served and published. 
The question, whether the material standard should aim at an approxima- 
tion to the Me? oy oh , was much debated. In favour of the latter it 
second second 
was argued that, so long as in England feet and grains were in general use, 
metre 
the 
second 
would be anomalous, and would entail complicated reductions in 
dynamical calculations. In favour of the — 
second 
new standards were to be established, those should be chosen which might be 
generally adopted, and that the metre is gaining universal acceptance. 
Moreover the close accordance between Dr. Siemens’s unit and the decimal 
multiple of the cee weighed in favour of this unit; so that the question 
secon 
was decided in favour of the metrical system. 
Tn order to carry out the above views, two points of essential importance 
had to be determined. First, the degree of accuracy with which the material 
standard could at present be made to correspond with the mote 2 
second 
secondly, the degree of permanency which could be ensured in the material 
standard when made, 
The Committee are, unfortunately, not able yet to form any definite opinion 
upon either of these points. 
Resistance-coils, prepared by Professor W. Thomson, haye been sent to 
Professor Weber; and he has, with great kindness, determined their resistance 
in electro-magnetic units as accurately as he could, It is probable that his 
determinations are very accurate; nevertheless the Committee did not feel 
that they would be justified in issuing standards based on these determina- 
tions alone. In a matter of this importance, the results of no one man could 
be accepted without a check. Professor Weber had made some similar deter- 
minations with less care some years since, but, unfortunately, he has not pub- 
lished the difference, if any, between the results of the two determinations, 
Indirect comparisons between the two determinations show a great discre- 
pancy, amounting perhaps to 7 per cent.; but it is only fair to say that this 
error may have been due to some error in other steps of the comparison, and 
not to Professor Weber’s determination. Meanwhile, it was hoped that a 
check on Weber’s last result would by this time have been obtained by an 
independent method due to Professor Thomson. Unfortunately, that gentle- 
man and Mr. Fleeming Jenkin, who was requested to assist him, have hitherto 
been unable to complete their experiments, owing chiefly to their occupation 
as jurors at the International Exhibition. The apparatus is, however, now 
nearly complete, and it is hoped will before Christmas give the required deter- 
minations. 
_ If Professor Weber’s results accord within one per cent. with these new 
determinations, it is proposed that provisional standards shall be made of 
German-silver wire in the usual way, and that they should be at once issued 
to all interested in the subject, without waiting for the construction of the 
final material standard. 
_ The construction of this standard may possibly be delayed for some con- 
siderable time by the laborious experiments which remain to be made on the 
absolute” permanency of various forms and materials, An opinion is very 
asad K2 
it was argued that, when 
and 
