JaNuARY 24, 1907 | 
NATURE 291 
realised at an early stage of the existence of the 
United States. Washington devoted much attention 
to this subject, and it was under his direction that in 
1791 a committee of the Senate entered upon a very 
full consideration of the questions involved. They 
reported in favour of a decimal system, and recom- 
mended the adoption of a standard of length divided 
into five equal parts, each of which would correspond 
to a foot. No legislative action was taken, however, 
to give effect to these recommendations. In 1819 a 
committee of the House of Representatives submitted 
a report advocating that models of the yard, bushel, 
and pound, conforming to those in most common use, 
should be made and adopted as the standard weights 
and measures of the United States. This proposal 
also proved abortive. The elaborate report prepared 
in 1821 by Mr. Secretary (afterwards President) 
Adams, a warm admirer of the metric System, was 
likewise without any immediate effect. The metric 
system was not seriously considered in the United 
States until 1866, when the use of the system was 
authorised by Congress. In 1889 copies of the inter- 
national metric standards were distributed by the 
International Committee to the various States which 
were parties to the Metric Convention. The copies 
received by the United States were immediately 
adopted as primary standards, and in 1893 a formal 
order of the Treasury Department recognised the 
international prototype metre and kilogram as fiunda- 
mental standards, and directed that the customary 
units, the yard, and pound were to be derived there- 
from. 
Chapters vi., vii., and viii. deal with the advantages 
which would be derived from the universal employ- 
ment of the metric system in commerce, manufac- 
tures, and medicine. The authors admit having a 
bias in favour of this system, and they make out a 
very good case for its general adoption, In the next 
chapter international electrical units are considered, 
and attention is directed to the benefits conferred upon 
electrical science by the introduction of the C.G.S. 
system at the instance of the British Association. 
The United States specifications for the practical 
application of the definitions of the ampere and volt 
were prepared by the National Academy of Science 
in 1895, in compliance with the provisions of an Act 
of Congress. These specifications, which are quoted 
in extenso on pp. 211-215, differ in some slight re- 
spects from those prepared in this country about the 
same time by the Board of Trade. 
A most instructive chapter is the tenth, which re- 
lates to the construction and comparison of standards. 
The various physical properties which should be 
possessed by primary standards are discussed, and an 
account is given of the different alloys which have 
been used in the construction of such standards. The 
relative merits of line and end standards are next 
considered, the method of subdividing a scale by 
means of a dividing engine being well described. 
It is mentioned that at the International Bureau the 
graduation of a metre into millimetres in this way 
occupies about sixteen hours. The footnote on p- 226 
NO. 1943, VOL. 75] 
quoted from Guillaume appears to contradict the 
statement in the text respecting the accuracy attain- 
able by this method. 
A very good description is given of the comparators 
employed in the verification of standards of length, 
and the mode of using them is explained. After some 
account of balances of precision, the British imperial 
standards of length and weight are described with 
illustrations. The name of Mr. Chaney, the late 
superintendent of weights and measures, is misspelt 
on p. 247, and the position which he occupied is in- 
accurately designated as Warden of the Standards. 
The latter office has been since 1878 an honorary 
adjunct to the permanent secretaryship of the Board 
of Trade. 
The chapter concludes with a simple and interest- 
ing explanation of measurement by means of wave- 
lengths of light. This method was originally only 
applicable to the measurement of very short intervals, 
but Michelson has extended its application to lengths 
of any magnitude. It is of great interest in metro- 
logy, since by making re-determinations from time 
to time positive testimony may be obtained as to 
whether any variation is taking place in the length 
of a standard. At the present day the permanency 
of bronze standards of length is regarded with 
suspicion by metrologists. The authors refer on 
p- 219 to the fact that many of the bronze copies of 
the British yard which were distributed to various 
nations and scientific institutions in 1855 are believed 
to have since undergone changes in length due to 
molecular rearrangement. This casts some doubt 
upon the invariability of the Imperial Standard Yard, 
which is made of the same material. The recent 
developments of Michelson’s method afford a ready 
means of deciding this important question. 
Some useful tables are appended, and a compre- 
hensive index brings this well-conceived work to a 
close. 
ITALIAN SCIENTIFIC WORKS. 
I grandi Trafori Alpini. By G. B. Biadego. Vol. i. 
Pp. xvi+1228; in addition to about 36 folded pages 
of tabular matter. Vol. ii. 30 large folded plates. 
(Milan: Ulrico Hoepli.) Price 45 lire (il. 16s.). 
Opere matematiche di Francesco Brioschi. Vol. iv. 
Pp. ix+418. (Milan: Ulrico Hoepli, 1906.) Price 
11 
I Motori a Gaz. By Vittorio Calzavara. 
424. Manueli Hoepli. (Milan: 
1906.) Price 4.50 lire. 
I Motori ad Esplosione, a Gas luce e Gas povero. 
By Ing. Fosco Laurenti. Pp. xii+36r. Manueli 
Hoepli. (Milan: Ulrico Hoepli, 1906.) Price 4.50 
lire. 
A Oa opening of the Simplon tunnel amid a flourish 
of Italian trumpets was a fitting opportunity 
for the publication of a book dealing with this and 
other mountain borings. That the author might have 
written a book on the Simplon tunnel alone is evi- 
denced by the fact that the part he devotes to this 
tunnel occupies the space of an average-size volume. 
Pp. xxx+ 
Ulrico Hoepli, 
