560 

affects the convenience of the reader. The articles in 
these volumes owe their outstanding value to the high 
authority of the authors, and it is unlikely that any 
one will consult an article without wishing to know 
who wrote it. He will look first at the beginning of 
the article, and not finding the name there he will 
probably turn to the end, where he will find the 
initials of the author. But it is very seldom that the 
initials of the best-known writers are familiar, so the 
reader has not yet got the information he requires. He 
may then recollect having seen a “ List of Contribu- 
tors’ at the beginning of the book, and here he will 
finally find the name belonging to the initials. Why 
should not the name of the writer have been put at 
the commencement of each article, where the reader 
naturally turns to find it ? 
Returning now to the articles themselves, they are 
so numerous, and deal with so many subjects, that it is 
quite impossible to notice them all, so we must content 
ourselves with a few words on one or two of the most 
important. 
In the group of articles dealing with measurement, 
the discussion of metrology by Mr. J. E. Sears, the 
Deputy Warden of the Standards, is of outstanding 
merit. Without going into a great deal of detail a 
clear account is given of the history of the British and 
metric standards of length, mass, and volume, followed 
by the theory of the methods used in comparing these 
standards with practical measuring apparatus. It 
will come as a surprise to most people to read in this 
article that two kilogram masses can be compared 
with a greater accuracy than two metre standards, the 
accuracy being one part in 108 and in 10? respectively. 
Mr. Sears’s discussion of the relative advantages of the 
British and metric systems is very valuable, and 
clearly indicates that the advantages are not all on one 
side. He is strongly opposed to attempts to hurry a 
change in Great Britain, and concludes: “ The only 
practical policy, and that which has actually been 
followed, is to give legal sanction to the alternative use 
of the metric system, and to trust to the processes of 
time to effect a gradual change. The efforts of those 
who desire to see the metric system in universal use 
would be more usefully employed in endeavouring to 
encourage and facilitate its voluntary adoption in this 
way, than in seeking to secure legal compulsion in 
advance of public desire.” 
This article on metrology is supplemented by 
separate articles dealing with the practical side of 
making measurements and comparing standards. 
These are nearly all written by members of the staff 
of the National Physical Laboratory, hence we have 
in them extremely valuable information of the actual 
methods used in this country. It is true that when 
NO. 2791, VOL. 111] 
NATURE 


[AprIL 28, 1923 
reading the articles one misses information on some 
point or other which would have been useful, but 
everything cannot be included in a book of finite 
dimensions, and on the whole the choice of subjects is 
good. The only criticism one” has to make in this 
respect, and it applies to the book in general, is that 
the articles are very uneven in the amount of detail 
given. There can be no doubt that “ gauges” are an 
important accessory in all accurate measurements of 
length, but are they so important as to justify the 
longest article in the volume and more than fifty 
per cent. more space than is given to the article on 
metrology itself ? 
this article we are taken outside applied physics into 
engineering practice. 
The chief article on the measurement of time is one 
by Prof. Sampson on clocks and time-keeping. It is a 
delightful article to read, for while it is short and not 
overburdened with detail, there is no difficulty in 
grasping the principles employed in the different forms 
of clocks described. After reading these thirty pages, 
one has the feeling (it may not be justified) that one 
knows all there is to know about clocks and their ways 
from the Glastonbury Abbey clock of 1325 to the 
latest Riefler. 
In the geophysical section we cannot help regretting 
that more space has not been allotted to the writers, 
even, if necessary, at the expense of the articles deal- 
ing with measurements, which in some cases, as 
already mentioned, are overburdened with detail. 
Some of the articles are so abbreviated as to lose a 
great deal of their usefulness ; this is particularly the 
case with the article on meteorological optics, which 
consists of only sixteen pages, while the descriptions of 
thirty-two different map projections are compressed 
into five pages. 
The articles by Sir Napier Shaw and Capt. Brunt 
indicate very clearly the great changes which have 
taken place during the present generation in the 
outlook of meteorologists. Meteorology has changed 
from being an observational study of weather and its 
changes to a study, largely deductive and mainly 
mathematical, of the atmosphere as a whole. It is not 
surprising, therefore, that one hears occasional com- 
plaints that the modern meteorologist is too fond of 
theory and long names. On the other hand, the 
recording of weather had gone on for many, many 
years without much progress in our knowledge of the 
“way of the air”; but in recent years the physicist 
and mathematician have looked our way and the 
progress has been startling. In this advance two 
One cannot help feeling that in~ 
names stand out pre-eminent in this country, Dines 
and Shaw, and both have written articles for this 
volume. Sir Napier Shaw’s article on “‘ The Thermo- 
