Marcu 7, 1912] 
OUR BOOKSHELF. 
Jelinek’s Psychrometer-Tafeln. Anhang: Hygro- 
meter-Tafeln von J]. M. Pernter. Herausgegeben 
von W. Trabert. Sechste Auflage. Pp. xii+ 
129. (Leipzig: W. Engelmann, 1911.) Price 
7 marks. 
solid little grain bodies, and in the course of the 
NATURE 5 
story I shall answer many of the questions with 
which you are now bubbling over; sweep away, I 
hope, most of the difficulties that are now puzzling 
| you. 
JeLinek’s psychrometer tables are among the best — 
known of the many humidity tables in use on the 
Continent. Originally prepared by Jelinek from 
the earlier tables of Regnault and Wild, the work 
has been successively re-edited by Hann and by 
Pernter, and now we have a further revision 
undertaken by Hofrat Trabert, the present director 
of the Austrian meteorological service. 
The new edition differs from its predecessor 
mainly in the method of treatment of the wet-bulb 
We are not sure that the ordinary reader will 
quite catch the idea the author wishes to convey, 
but she becomes much more lucid in writing about 
the social aspects of the industries as distinguished 
from the more purely technical side. The descrip- 
tions of the sugar plantations, of the school for 
the negroes, and of Georgetown have an air ef 
reality that cannot fail to appeal to the reader, 
whilst the accounts of the milling and extraction 
| processes are equally attractive. Nor are economic 
readings at temperatures below the freezing- | 
point. 
water vapour used hitherto were those for vapour 
in equilibrium with supercooled water, although 
in practice the wet bulb is normally coated with 
ice. The present edition has been amplified by 
the addition of a table of saturation pressures of 
water vapour in equilibrium with ice, taken from 
the results of Scheel and Heuse, and on this table 
has been based a new set of tables fer finding the 
vapour pressure and relative humidity from read- 
ings of dry and wet bulb thermometers at tem- 
peratures below the freezing-point when the wet 
bulb is covered with ice. The results for higher 
temperatures have been entirely recalculated, but 
their general arrangement remains unchanged. 
The tables differ from most humidity tables in 
general use in that allowance is made in them for 
variations of wind velocity. The figures 
printed are applicable to the readings of screened 
thermometers under conditions of light or moderate 
wind, but by the application of simple corrections 
to the wet bulb readings they can be rendered 
applicable on the one hand to readings in still air, 
and on the other to readings taken during gales or 
strong winds, or with an aspirated psychrometer 
such as the Assmann instrument. 
as 
Peeps at Industries: Sugar. 
Pp. vii+88. (London: 
Price 1s. 6d. net. 
Tuis little book is the first volume of a series 
intended to deal with industries in the same way 
as “Peeps in Many Lands” has dealt with 
countries. The general get-up is attractive, the 
illustrations are good, and the reader is never 
fatigued by having too much serious matter pre- 
sented to him cn any one page. The whole 
ground is covered, both beet and cane sugar com- 
ing within the purview of the author, and the 
descriptions range from an account of a Demerara 
estate to a Belgian sugar factory and a London 
refinery. The style of the book may be judged 
by the following quotation :—“ Sugar is hatched 
from germs which inhabit the sap of certain 
plants. In the birth stage it takes the form of 
tiny grains. I am going to tell you quite simply 
By Edith A. Browne. 
A. and C. Black, 1g1t.) 
and briefly the way in which the germs become | 
NO. 2210, VOL. 89| 
The values of the saturation pressure of | 
| to describe its scope. 
questions left untouched, and although no actual 
tables of statistics are given—they would indeed 
have been out of place in a volume of this nature-— 
the author succeeds in conveying the essential 
facts relating to the economic position. Alto- 
gether the little book is one that will give the intel- 
| ligent child the sort of information he wants about 
the subject. 
Photographic Lenses: A Simple Treatise by 
Conrad Beck and Herbert Andrews. Seventh 
edition, completely revised, with index. Pp. 324. 
(london: R: and -J. Beck, Ltd; nid) Price 
rs. net. 
Many thousands of this volume having been sold 
in the previous editions, there is but little need 
It will be sufficient to say 
that the authors do not intend in it to give a 
full explanation of the laws that underlie the 
| construction of photographic lenses, but rather to 
provide a practical guide for the user of lenses 
that he may be able to use them to the best 
advantage. The volume is excellently illustrated 
with diagrams that make clear the principles of 
elementary optics, the construction of various 
objectives, the comparative results of their tests, 
and also examples of the actual work that they 
enable the photographer to do. For those. who 
wish to go a little further into the subject there 
is an appendix on “Equivalent Planes,” and a 
' second appendix in which a lens-testing optical 
bench is described, with the manner of using it. 
The lenses illustrated and referred to are all of 
Messrs. Beck’s manufacture, but that fact does 
not, in a practical sense, limit the usefulness cf 
the book. The present edition is brought up to 
date, especially with regard to recent anastigmats, 
| and it is provided with a very good index. 
Practical Botany. By Dr. F. Cavers.. Pp. xvi+ 
408. (Cambridge: University Tutorial Press, 
letds ror), Brice 45.) 6a: 
TakING a general view, there are four different 
sections recognisable in this students’ practical 
botany: histology is placed first, then follow 
physiology of growth and nutrition, physiology of 
movement, and finally a sketch of practical work 
on selected cryptogamic types. There 1s, of 
course, no reason why teachers should begin with 
histology; on the contrary, experience points to a 
