= 
SEPTEMBER 25, 1913] 
NATURE 
gratulated on the fair and temperate manner in 
which they have brought their case before the 
court of public opinion. Pain and suffering are 
unfortunately inseparable from the lot of many 
kinds of domesticated animals, as well as of those 
wild species which are hunted for sport or for their 
spoils; but it is the bounden and paramount duty 
of all civilised nations to see that these are reduced 
to the smallest possible minimum. Those who read 
this book—and it is, for the most part, at any rate, 
very painful reading—will, however, be convinced 
that even in our own country matters too often are 
by no means as they should be in this respect. In 
fact the authors have, unhappily, in many in- 
stances, a very strong, and in almost every in- 
stance a very sad, case; and it is sincerely to be 
hoped that their book may be the means of bring- 
ing to pass a better state of affairs in regard to our 
treatment of the lower animals in such cases as 
amendment and amelioration are most urgent and 
at the same time practicable. Apart from the 
ruthless slaughter of birds for their plumage— 
accompanied too frequently by the lingering 
starvation of their helpless young—one of «the 
worst and most pitiable cases in the whole sad 
story is the treatment meted out to. worn-out 
horses; and it must indeed be a hardened heart 
which is not rent by the illustrations depicting 
these wretched animals on their last journeys. 
Fortunately, several European Governments are 
already awake to the need of stringent measures to 
remedy this crying evil, and we trust the present 
volume may give a further stimulus to their 
efforts. Roos. 
Les Moteurs Thermiques dans leurs Rapports 
avec la Thermodynamique. Moteurs 4 explosion 
et & Combustion. Machines Alternatives a 
Vapeur. Turbines 4 Vapeur. By F. Moritz. 
Pp. vi+297. (Paris: Gauthier-Villars, 1913.) 
Price 13 francs. 
In writing this book on heat engines the author 
has divided very unequally the space given to 
engines operating with external combustion and 
those in which combustion takes place inside the 
cylinder. By far the larger part is given up to 
the steam engine, and particularly the steam | 
et P f _helium. Also, the Ritz series of infra-red hydrogen 
turbine. As is usual in French books, mathemati- 
cal analysis is the natural line of approach to any 
difficult problem, however obscure the relationship | Apart from this, I find it difficult to believe that the 
The book is divided into | 
of theory and practice. 
six chapters, of which the first two relate to the 
laws of thermodynamics—and a very careful and 
complete statement of them is given—to gaseous 
meant by entropy. 
The twenty-five pages of chapter iii. are made 
to suffice for the application of preceding 
theory to the gas engine, and as a natural con- 
sequence of such compression the conclusions 
reached are incomplete. The gaseous mixture 
used in the gas engine is throughout assumed to 
have a specific heat quite independent of all tem- 
perature changes—an assumption which naturally 
removes almost all practical value from any con- 
clusions which may be arrived at on theoretical 
NO. 2291, VOL. 92] 
95 
grounds. The chapter concludes with the follow- 
ing quaint suggestion :—‘‘On peut en tirer des 
conclusions practiques intéressantes, par example, 
sur l’influence de la circulation d’eau autour des 
cylindres. Nous laissons au lecteur le soin de 
faire cette comparison pour tous les cas qui 
peuvent se présenter a lui.” 
Chapters iv., v., and vi. (some two hundred 
pages) are given up to piston steam engines and 
steam turbines. The author shows much skill in 
his analysis of the theory of jets and of turbine 
flow; he treats very fully also of turbine leakage, 
and uses freely the entropy diagram to illustrate 
his meaning. Students of the steam turbine will 
find M. Moritz’ book both interesting and stimu- 
lating. 
LETTERS TO THE EDITOR. 
{The Editor does not hold himself responsible for 
opinions expressed by his correspondents. Neither 
can he undertake to return, or to correspond with 
the writers of, rejected manuscripts intended for 
this or any other part of Nature. No notice is 
taken of anonymous communications.] 
The Spectra of Helium and Hydrogen. 
Wir regard to Mr. Evans’s communication to 
NaturE, September 4, p. 5, I should like to remark 
that while I have for some time recognised that the 
experimental evidence, on the whole, seems to be in 
favour of helium as the origin of the new lines 4686, 
&c., it should not be too hastily concluded that they are 
not due to hydrogen. Mr. Evans appears to have 
succeeded in eliminating the ordinary spectroscopic 
indications of hydrogen from his helium tubes, but is 
it not possible that, under the special conditions of 
the strongly disruptive discharge, with helium also 
present, residual hydrogen may be represented only 
by the new lines? This would not be the only known 
case in which the presence of helium aids the de- 
velopment of the spectrum of another gas with which 
it is mixed. I have observed this effect in the case 
of the series of bands of carbonic oxide which are 
characteristic of the tails of comets; these bands are 
| of very feeble intensity at the low pressures necessary 
for their approximate isolation in the spectrum of the 
pure gas, but I have seen them greatly intensified 
when carbonic oxide was present as an impurity in 
lines was found by Paschen to be brighter in a mixture 
of hydrogen and helium than in hydrogen alone. 
close agreement of one set of lines with the principal 
series calculated for hydrogen by Rydberg is merely 
accidental. 
Dr. Bohr’s theory (Phil. Mag., July, 1913) does not 
cycles and to a concise explanation of what is | 2t Present seem to me to give much evidence for 
| helium, in preference to hydrogen, as the origin of 
the lines in question. The formula derived from the 
theory gives no better agreement with the observations 
than that of Rydberg, so far as the two are com- 
parable, and apparently requires that the seven ob- 
| served lines, beginning with 4686, should be capable 
of arrangement in a single series. I think, however, 
that the lines cannot be so united within the limits 
of error of observation, though very nearly so, and 
I believe that my separation into two series converg- 
ing to the same limit is correct. The necessity for 
two series is rather more clearly indicated in the case 
of the analogous series of magnesium spark lines 
