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NATURE 
[JuLy 3. 1902 
G. Schiaparelli, and the result is a work of which the 
present is the first volume. It contains fifty-four of 
Brioschi’s papers, of which forty were originally published 
during the period 1851-1857 in the Anmali di Scienze 
matematiche e fisiche under the editorship of Barnaba 
Tortolini, and the remainder appeared in the Anmaili di 
matematica pura ed applicata, which formed a continua- 
tion of the previous journal, during the years 1858-1861. 
The last of the series is Brioschi’s classical monograph 
on the theory of covariants and invariants of binary 
forms and their principal applications. The arrangement 
adopted has thus been to classify Brioschi’s papers 
according to the journals in which they are published 
and not according to date or subject-matter. 
The committee placed the principal work of editing the 
volumes in the hands of Profs. Beltrami and Cremona, 
and on the death of the former the task was continued 
by Prof. Valentino Cerruti, the papers in the present 
volume being revised in addition by Profs. Pascal, 
Gerbaldi, Loria, Pittarelli, Reina and Tonelli. To these 
names must be added those of Profs. Bianchi and 
Capelli in connection with the revision of material for 
succeeding volumes. 
A photogravure portrait of Brioschi forms a frontis- 
piece, and a short history of his life will appear at the 
end of the complete work, forming a lasting monument 
to the great Italian mathematician. 
Webster's 
Language. 
25,000 Words and Phrases. 
Ph. D., LL.D., Editor-in-Chief. 
and Sons.) Price 2 guineas net. 
International Dictionary of the English 
To which is now added a Supplement of 
Edited by W. T. Harris, 
(London : George Bell 
No more convincing proof of the extent to which the 
English language has been enriched as a result of the 
wonderful activity in scientific circles during recent 
years could be found than this new edition of the world- 
renowned ‘‘ Webster.” The supplement, which dis- 
tinguishes this from the last edition of the dictionary, is 
largely composed of scientific terms and technical ex- 
pressions which have come into existence during the last 
decade. It is only necessary to glance down a list of 
the names of the men of science who have assisted Dr. 
Harris in the preparation of this substantial addendum 
to satisfy oneself that the definitions will prove clear, 
accurate and complete. Repeated tests have shown that 
such anticipations are well founded, a conclusion that 
will not seem surprising when it is stated that among the 
assistants on whose services the Editor-in-Chief has been 
able to rely are such scientific experts as Prof. E. S. 
Dana, Prof. G. K. Gilbert, Dr. E. S. Holden, Dr. T. C. 
Mendenhall, Prof. E. L. Nichols, Prof. I. Remsen, Prof. 
A. E. Verrill, Prof. L. F. Ward, and many others of 
equal authority. The dictionary will continue to merit 
the confidence with which it has long been regarded. 
Education and Empire. Addresses on certain Topics 
of the Day. By Richard Burdon Haldane, M.P., 
LL.D., K.C. Pp. xvi + 195. (London: John Murray). 
Price 5s. net. 
IN the first two addresses in this volume Mr. Haldane is 
concerned entirely with educational problems, and in 
both of them pleads in a convincing manner for more 
earnest attention to the great need of increased facilities 
for higher technical instruction and for scientific research 
in this country. The comparisons which are here 
instituted between what is done in the United Kingdom 
and in Germany and the United States of North America 
in the matter of providing technical colleges and 
laboratories for scientific research should, if anything 
will, explain to our manufacturers and merchants the 
reason for the phenomenal success of our trade rivals. 
NO. 1705, VOL. 66] 
LETTERS TC FHEVEDI TOR: 
The Editor does not hold himself responsible for opinions ex- 
pressed by his correspondents. Neither can he undertake 
to return, or to correspond with the writers of, rejecied 
manuscripts intended for this or any other part of NATURE, 
No notice 2s taken of anonymous communications.\ 
Mr. Marconi’s Results in Day and Night Wireless 
Telegraphy, 
I CAN assure Prof. Joly that his explanation (p. 199) will 
not do, 
The observed effect, which if confirmed is very interesting, 
seems to me to be due to the conductivity, and consequent 
partial opacity, of air, under the influence of ultra-violet solar 
radiation. 
No doubt electrons must be given off from matter (dust as 
well as other matter) in the solar beams ; and the presence of 
these will convert the atmosphere into a feeble conductor. 
Conducting power in the sea-water surface assists and guides 
the waves, retaining them in two dimensions after the same 
fashion as a telegraph wire retains them in one; but conduc- 
tivity in the dielectric itself will tend to dissipate and enfeeble 
the waves, by a process of reflection resulting in some amount 
of distortion. OLIVER LODGE. 
June 27. 
Kinetic Theory of Planetary Atmospheres. 
In the Astrophysical Journal for November, 1901, is printed 
a paper of mine in the first part of which a method is pro- 
posed for determining the mean temperatures of the atmo- 
spheres of the planets and those of their surfaces. In the 
second part of the paper an attempt was made with the use of 
these temperatures to determine the composition of the atmo- 
spheres of the planets by the ‘‘empiric” method proposed by 
Dr. Johnstone Stoney and based on the supposition that 
helium escapes from the earth’s atmosphere. The most 
probable velocity of the molecules of helium is 1093 metres per 
second at 15°,C. (the mean temperature of the earth’s surface), 
and the velocity sufficient to overcome the earth’s attraction is 
11,170 metres per second. Hence it has been inferred that a 
gas escapes from the surface of the planet, if the most probable 
velocity of its molecules is 10°22 times less than that required to- 
overcome the planet’s attraction. 
Prof. G. H. Bryan (NATURE, No. 1698, p. 54) has remarked 
that according to his and Mr. Cook's calculations, founded on 
the kinetic theory of gases, helium cannot escape to any sensible 
extent from the earth’s atmosphere by the motion of its mole- 
cules among themselves. But the assumption that helium cannot 
be retained by the earth’s attraction is arbitrary. It is possible 
that helium exists in our atmosphere in only a very smalb 
quantity, because it is contained in the interplanetary medium 
in very insignificant proportions ; its escaping, if it occurs, is 
effected, perhaps, by ordinary diffusion, We know several 
substances, as thorium, osmium, &c., which are very rare 
minerals, though their atomic weight is great. It is possible, 
moreover, that even hydrogen can be retained by the earth ; it 
seems to be confirmed by the observations of M. Gautier 
(Bulletin de la Soc, chim.,de Paris, December 5, 1900, p. 884): 
and Lord Rayleigh (P27. Mag., vol. iii., pp. 416-422, 1902), 
who have found free hydrogen in atmospheric air. 
Assuming the last supposition, we must substitute for the 
number 10°22 some other less than 7°42 (=1,44%°, where 1505. 
is the most probable molecular velocity of hydrogen at 15° C.), 
for instance, 7, 6, or 5, in order that an appreciable number 
of molecules may attain the speed sufficient to carry them to 
infinity; and consequently table iii, in my paper must be 
changed correspondingly. E. RoGovsky. 
The Coloured Sunsets. 
THE recent fine weather has enabled one to observe the sun- 
sets and after-glows under very favourable circumstances, and 
the most striking feature observed was the predominance of the 
beautiful salmon-colour tinge, which became most intense when 
the after-glow was brightest. 
Practically none of the sunsets observed were strikingly red, 
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