JULY 9, 1914] 
western part of the South Island, when, owing 
to the roughness of the way and a wrong route, 
four days’ provisions had to serve for seven, and 
the party might not have survived except foi some 
chance birds that were killed by stones. 
The last chapters describe Dr. Bell’s journeys 
in the Southern Alps, and give a brief summary 
of the geography and climate of New Zealand. 
Most of the author’s results have been stated in 
his geological papers, and as the present work 
is essentially popular he has excluded technical 
matter; but he writes of different areas with the 
intimate knowledge gained in the course of his 
surveys. The book gives an interesting account 
of the author’s journeys, and is a useful record 
of the present conditions of some of the less- 
Mount Balloon, near the track to Milford Sound. From ‘ The Wilds of 
Maoriland.” 
known parts of New Zealand; it conveys a good 
impression of the magnificence and variety of New 
Zealand scenery, but indicates that the conditions 
of travel there are exceptionally rough and the 
accommodation often poor. 
RECENT PROGRESS OF THE METRIC 
SYSTEM. 
E have received a copy of a report on the 
progress of the metric system which was 
presented by Dr. Guillaume at the meeting of the 
fifth general conference on weights and measures 
held in Paris in October last. A previous report 
1 ‘Les récents Progrés du Systéme métrique.” By Ch. Ed. Guillaume. 
Pp. 118. (Paris: Gauthier-Villars, 1913.) Price 5 francs. 
NOs 2332, VOL. 93] 
NATURE 
483 
by Dr. Guillaume on the same subject was re- 
viewed in these columns in 1908 (April 30). In 
the first part of the present work the author deals 
with the question of standards of measure and 
weight. As regards the use of vitreous quartz or 
silica for the construction of standards of length 
he points out that recent investigations tend to 
show that this material is unsuitable for the pur- 
pose, owing to inconstancy of length. A _ his- 
torical account is then given of the attempts made 
at the international bureau to find an appropriate 
material for the construction of standards of 
length for use in the laboratory, where the ques- 
tion of cost prohibits the employment of iridio- 
platinum. These efforts led to the important 
series of investigations with respect to the metro- 
logical properties of the alloys of nickel and steel, 
and to the discovery by Dr. Guillaume of the alloy 
of minimum expansion, now well known as 
“invar.” The feeble expansion of invar would 
render this alloy an ideal material for standards 
of precision were it not.for its tendency to in- 
stability. In spite of this drawback, however, its 
use for secondary standards deserves careful con- 
sideration in cases. where an accuracy of one part 
in a million is sufficient. 
Researches have also been made with the view 
of finding suitable alloys to replace iridio-platinum 
for the construction of secondary standards of 
weight. Various non-magnetic alloys of nickel 
were investigated. Of these constantan was 
found to be unsuitable, owing to its lack of 
durability, but ‘‘baros,’’ formed by the addition 
of small quantities of chromium and manganese 
to commercial nickel, has proved to be more 
satisfactory. Tungsten, in virtue of its hardness, 
high density and durability, promises to be a very 
suitable material, especially as it seems likely that 
this metal will soon be obtainable at a relatively 
low price. Dr. Guillaume also discusses the re- 
sults of recent researches with reference to the 
employment of wave-lengths of light in metrology, 
and points out that the gases krypton and neon 
both afford special advantages as regards inter- 
ference measurements. 
A section is devoted to legislation with respect 
to the metric system in various countries since 
the fourth general conference. During the past” 
six years the system has been made obligatory in 
several countries, notably Denmark, Siam, the 
Belgian Congo, and certain of the republics of 
Central America. Dr. Guillaume considers that 
the difficulties standing in the way of the adoption 
of the system in Great Britain and the United 
States have been greatly exaggerated by its 
opponents. He urges that in the engineering 
trade, for example, the proposed innovation would 
not, as is. often alleged, necessarily put out of use 
all machines the dimensions of which could not 
be expressed in convenient figures in terms of 
metric units; the first reform would be simply to 
give the metric equivalents of the quantities 
hitherto expressed in Imperial units; later on, 
when the machines were being replaced by new 
| ones in the usual course, any slight modifications 
required might be introduced. 
