320 
WATURE 
| 
[MAY 36), 1902 
of students. The method of treatment of the 
thermodynamic principles is good, and will be 
readily comprehended by any reader who has but 
slight knowledge of higher mathematics. 
The earlier chapters deal with heat, tempera- 
ture, energy, the first law of thermodynamics, and 
the formation and expansion of steam. These 
lead to very useful chapters on the theory of 
reciprocating engines and on their thermal per- 
formances in practice. Sufficient is included on 
valve gears and indicator diagrams to enable the 
student to understand the ordinary gears and to 
detect any defects in practical working. A con- 
siderable section of the book is devoted to the 
steam turbine, and this portion is excellent, both 
as regards the treatment of the laws of expansion 
in nozzles, and also the explanations given of the 
action of the more common types of turbines. 
Some notes on propulsion, coal consumption, in- 
ternal combustion engines, and refrigerators are 
also given. 
As the book is rather a collection of expanded 
notes than a comprehensive text-book, the author 
has wisely omitted any elaborate descriptive 
drawings. Such drawings as appear give all the 
information required to enable the principles dis- 
cussed in the text to be understood readily. 
Within its scope the book can be recommended 
as supplying a useful supplement to lecture 
courses dealing with the subject. 
Gardens in their Seasons: a Nature Book for 
Boys and Girls. By C. von Wyss. Pp. 64. 
Illustrated. (London: A. and C. Black, 1912.) 
Price 1s. 6d. 
Wonders of Plant Life. By S. Leonard Bastin. 
Pp. x+136. Illustrated. (London: Cassell 
and Co., Ltd., 1912.) Price 3s. 6d. net. 
Tue first of these books can be depended upon 
to arouse in children a love for both the plants 
and animals of the garden. It is for the most 
part well and simply written, and with the excep- 
tion of the last one in the book, the illustrations 
are charming. One cannot altogether concur 
with the statement that the crocus lays eggs, 
nor is the author accurate in his remark that 
“none of us know” how food is constructed in 
green leaves. The statement on p. 64 that the 
thick skins of the holly leaves “keep in the 
warmth of the body, and frost cannot penetrate,” 
is not only untrue, but very misleading even to 
children. 
The second volume cannot fail to interest the 
young botanical student, but it is unfortunate 
that the author has not confined his attention 
entirely to the popular side of the subject. As 
soon as he enters the domain of scientific botany, 
especially physiological, he is obviously out of 
his depth, as can be verified by reference to many 
of his statements in the chapter on “The Feelings 
of Plants,” and to his account of the reproduction 
of the fern on p. 66. Many of the illustrations 
are very good, and that of the Yucca in flower, 
facing p. 38, is excellent. As in so many books 
of this kind, “fertilisation”? is used where 
pollination is meant. 
NO. 2222, VOL. 89] 
LEV LERS © RODE ED TT OR 
(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 Ammonia Flame. 
Wiru reference to Mr. Egerton’s interesting letter 
in Narure of May 16, my colleague, Prof. Fowler, 
reminds me that he photographed the spectrum of 
the ammonia flame at the time that we were investi- 
gating the spectrum of the active nitrogen glow. 
Although the general colour of the flame is not un- 
like that of the nitrogen glow, he found nothing 
really in common between their spectra in the visual 
region. Re-examination of the negatives confirms 
this conclusion. I fear, therefore, that we cannot 
connect the ammonia flame with active nitrogen, 
interesting though such a connection would be. 
Observations on the ammonia-flame spectrum are 
not new; an account of what has been done in this 
direction will be found in Kayser’s ‘‘ Handbuch der 
Spectroscopie,”’ vol. v., p. 835. 
I take this opportunity of referring to another 
flame phenomenon which is connected with the after- 
glow of electric discharge. E. Becquerel (La 
Lumiére, vol. i., p. 196) remarks (and I have verified) 
that a colour may be observed at the tip of the oxy- 
hydrogen flame identical with the greenish-yellow 
of the afterglow in air. The latter, as I have shown 
(Proc. Roy. Soc., A, vol. Ixxxvi., p. 57, I911), is 
characteristic of nitrogen peroxide, and may be 
imitated by passing nitric oxide or peroxide into a 
Bunsen flame. The colour of the tip of the oxy- 
hydrogen flame is no doubt due to the presence of 
nitrogen peroxide, which is formed by oxidation of 
atmospheric nitrogen at the high temperature, and is 
stimulated to luminosity in just the same way as 
nitrogen peroxide artificially introduced. 
There is nothing new in the oxidation of nitrogen 
attendant on the combustion of oxygen and hydrogen 
in its presence— indeed, the effect has been recog- 
nised as a source of error in gas analysis. At the 
time when Lord Rayleigh was working out the 
method of isolating argon by oxidation of atmo- 
spheric nitrogen, he was able, I remember, to detect 
the presence of nitrogen peroxide by its smell on 
entering an ordinary room lighted by incandescent 
gas lamps. Ri Je SrRurrs 
Imperial College of Science and Technology, 
May 22. 
The Free-living Marine Nematodes. 
I HAVE recently paid a short visit of a few days to 
the Port Erin Marine Biological Station in order to 
gain some idea of the free-living marine nematodes 
and their distribution. The subject is one that has 
not received much attention in this country since the 
publication in 1866, in the Transactions of the 
Linnean Society, vol. xxv., of Bastian’s monograph 
of the Anguillulidz. 
The nature of the food is one of the most obscure 
points in connection with this much neglected group, 
but I have been able to determine what it is in at 
least one of the marine species. Owing to pressure 
of work on the terrestrial nematodes, more extended 
investigation of the marine forms is at present 
impossible, and must be left until some future date. 
Therefore I have thought it better merely to report 
the matter now, and to publish my observations later 
on when they have been considerably amplified. 
