THURSDAY, SEPTEMBER 25, 10913. 
ELECTRICAL STANDARDS. 
Reports of the Committee on Electrical Standards 
appointed by the British Association. Pp. 
xxiv +783+10 plates. (Cambridge: University 
Press, 1913.) Price 12s. 6d. net. 
HE reissue by the Cambridge University 
Press of the annual Reports of the Com- 
mittee on Electrical Standards, with Mr. F. E. 
Smith as editor, has placed in our hands in a 
convenient form an extremely interesting chapter 
of the history of scientific research in this country. 
The committee was first appointed in 1861, as the 
outcome of a paper on the subject by the late Sir 
Charles Bright and Mr. Latimer Clark. At that 
time no generally recognised system of elec- 
‘trical units existed, and its initial object was to 
decide on the most convenient unit of resistance 
and embody it in a material standard. Its first 
members were Profs. W. Thomson, Williamson, 
Wheatstone, and Miller, Dr. Mattiessen, and Mr. 
Jenkin. Seven other members, including Profs. 
Maxwell, Stewart, and Dr. Joule, were added in 
1863, and four others, including Prof. C. Foster 
and Mr. Hoskin, in 1867. 
During the first eight years of its existence the 
committee displayed great activity, its first six 
annual reports covering 290 pages of the book, 
the contributions of the members named _ being 
especially prominent. Asa result a unit equal to 
10? cm. per second had been adopted, and 
named at first the Ohmad and subsequently the 
Ohm. This had been embodied in wires of several 
_ materials, and in a column of mercury of a square 
millimetre section and 10485 cm. long. 
In its seventh report in 1870 the committee com- 
plained of the difficulty of getting its many 
members together, and of the remissness of its 
subcommittees, and suggested that the further 
problems of selecting units of capacity, difference 
of potential and current, and the construction of 
standards, be dealt with by new committees. 
Neither the old committee nor the suggested new 
committees were appointed, however, until 1880, 
when other measurements had cast doubt on the 
accuracy of the committee’s ohm, and four of its 
original members, and nine others, were consti- 
tuted the re-appointed committee charged with the 
construction of standards of resistance, capacity, 
and electromotive force. 
For the next twenty years the activities of the 
committee centred round the Cavendish Labora- 
tory at Cambridge, where under Lord Rayleigh 
the value of the old ohm was shown to be more 
than 1 per cent. too low, and under Dr. Glaze- 
NO. 2291, VOL. 92] 
NATURE gl 
brook a systematic comparison of the various 
copies of the ohm was kept up for many 
years as° a. test of their relative” per- 
manency. Standard capacities were also con- 
structed, but the middle years of this period were 
chiefly occupied with the Clark cell as the standard 
of electromotive force. The end of the period 
brought the question of the measurement of 
current by the “current balance” to the fore, and 
for the next decade the work of the committee 
was centred in the National Physical Laboratory, 
and fell largely on the shoulders of Mr. F. E. 
Smith. Under the new conditions the order of 
accuracy of the results obtained was rapidly in- 
creased, and at the present time measurements of 
electrical resistance, current, and electromotive 
force can be made in terms of the international 
units with an accuracy of about five parts in 
100,000. 
The work of constructing practical electrical 
standards for which the committee was appointed 
fifty years ago has therefore been achieved, and 
each of the twenty-two members who formed the 
committee last year when it dissolved, may look 
back with satisfaction to his share in an advance 
of national and international importance. 
The book is well printed, the type used is larger 
than that of the British Association Reports, and 
the spacing between the lines is somewhat greater. 
The index covers ten pages, and much facilitates 
the use of the work. A list of the whole of the 
members of the committee, with their years of 
service, is given in the introduction, but the 
familiar headings to the reports with the names of 
the members, and the specification of the chair- 
man and secretary, have been omitted, much to 
the present writer’s regret. Cobia 
TRADE WASTE WATERS. 
A Text-book on Trade. Waste Waters: their 
Nature and Disposal. By Dr. H. Maclean 
Wilson and Dr. H. T. Calvert. Pp.. xii+ 340. 
(London: C. Griffin and Co., Ltd., 1913.) Price 
18s. net. 
ANUFACTURING prosperity implies the 
M increasing production of trade waste 
waters, and the increased pollution of our rivers 
unless the greatest care is taken to utilise or 
minimise such waste, or processes of purification 
more efficient than many of those in general use 
are adopted. 
In north and central England the problems atten- 
dant upon the utilisation or purification of waste 
liquors are numerous and of special importance, 
but there are few districts in this country where 
difficulties do not occasionally arise. The authors 
- of this work, as chief officials of the West Riding 
E 
