APRIL 4, 1912] 
THE MEASUREMENT OF REFRACTION. 
Refraktometrisches Hilfsbuch. By Prof. W. A. 
Roth and Dr. F. Eisenlohr. Pp. viii+ 146. 
(Leipzig: Veit and Co., 1911.) Price 6 
marks. 
MEASUREMENT of the refractive power 
A of a liquid, while of considerable 
practical value for identifying the liquid or for 
ascertaining its freedom from impurities, is of 
far greater importance from the purely scientific 
point of view. Investigation has shown that 
for each substance a relation subsists between 
the refractive index and the density that is 
independent of the temperature; and, further, 
that the specific refractive index, as this relation 
is termed, may be calculated when the molecular 
constitution is known. Various formule have 
been suggested for the specific refractive index. 
Thus Gladstone and Dale on empirical grounds 
n-1 : as 
proposed —— ; while a more accurate expression 
a 
nm>—-1I I : : 
- > was afterwards put forward simul- 
7-2 
taneously from theoretical considerations by 
| 
two men of nearly the same name, Lorenz in | 
Copenhagen and Lorentz in Leyden. 
The little book which Prof. Roth and Dr. Eisen- 
lohr have prepared will prove invaluable to 
investigators in the subject, and, in fact, to all 
who have need to measure the refractive indices 
of liquids with the highest possible degree of 
accuracy. They fully describe the various forms 
of refractometer in use for the purpose and the 
methods of using them, and state the corrections | 
necessary when the temperature of the observa- 
tions differs appreciably from the standard, and 
give in tables the indices corresponding to the 
divisions in instruments with arbitrary scales. 
The old method of determining the deviation of a 
beam of light passing through the liquid contained 
in a hollow glass prism has entirely given way to 
the more convenient and more accurate method 
based upon the principle of total-reflexion. They 
describe further with equal fulness the method of | 
finding the density by means of a pyrometer, | 
point out the corrections required by the expan- 
sion of the glass, and give tables to facilitate their | 
application. Towards the end of the book the 
authors show by a few examples how closely the 
observed value of the molecular refractive index 
agrees with that deduced from the constitution, 
and discuss the meaning of the sensible differences 
that occur in certain groups of substances. The 
book closes with some useful tables, and a small 
book of five-figure logarithms is enclosed in a 
pocket within the cover. 
NO. 2214. VOL- 8q} 
| motive, the author deals with it in chapter i. 
OUR BOOKSHELF. 
The Modern Locomotive. By C. Edgar Allen. 
Pp. ix+175. (Cambridge: The University 
Press, 1912.) Price 1s. net. 
Tuis volume belongs to the series of Cambridge 
Manuals of Science and Literature, and taken as 
a whole the information given in it is up to date 
and described in terms clearly evident to the lay 
reader. 
As the boiler is “the heart and soul” of a loco- 
He 
claims that the multitubular boiler as fitted to the 
“Rocket ” originated with Mr. Booth, the secre- 
tary of the Liverpool and Manchester Railway— 
an unwarrantable claim, and one made for the 
first time, so far as the present reviewer’s know- 
ledge of locomotive history goes. The “Rocket's” 
multitubular boiler was to the designs of William 
Henry James, son of William James—the father 
of railways. In an agreement dated September 1, 
1821, W. H. James’s patent was assigned to 
Messrs. G. Stephenson and Wm. Lush on certain 
terms, and it was with this boiler the prize of 
sool. was won at Liverpool in 1827 by the 
“Rocket.” 
The chapter is interesting ; it illustrates how old 
ideas are resuscitated even in locomotive engineer- 
ing; for instance, the spark arrestor, so called, 
illustrated in Fig. 9, and the variable blast pipe in 
Fig. 10, were both in use on the Manchester, 
Sheffield, and Lincolnshire Railway, now the 
Great Central Railway, in the year 1878. The 
question of a satisfactory spark arrestor is a 
prominent one at the present time, and many ex- 
periments are in progress: a combination of 
Louvre plates on the smoke box and an ash-eject- 
ing arrangement on the blast pipe is now giving 
satisfactory results. Chapter iii. is devoted to 
modifications and improvements in the standard 
boiler. 
The volume will be found to contain much in- 
teresting and useful information. It should be 
of much use to those of the general public who 
take an intelligent and intense interest in the 
locomotive. To the apprentice in the works the 
information should be of particular value. 
ING Me Ue: 
The Gardener and the Cook. By Lucy H. Yates. 
Pp. x+260. (London: Constable & Co., Ltd., 
1912.) Price 3s. 6d. 
Tus little book is attractive in more ways 
than one. It stimulates the imagination as to 
| what can be done both in garden and kitchen, 
{ 
more especially in the kitchen. It leaves, however, 
a little sediment of despair in the mind, after all, 
for where out of France are “Charlottes” to be 
found? So much depends upon “Charlotte,” the 
cook. 
What use is a kitchen-garden, however success- 
ful, if you have a stupid, obdurate “Charlotte,” 
who will not see that to be a real cook is to have 
a talent for taking pains, and that to be careful 
and wise is not to be mean? Who can persuade 
our. English cooks that cooking is an art, and 
