Fune 25, 1885] 
and of the ground, at a depth of 1 inch, 809; 9 inches, 
80°7 ; 20 inches, 82°°6 ; 60 inches, 83°8 ; and 132 inches, 
83°°2. Itis desirable that the errors of these underground 
thermometers were ascertained. 
Down to the close of 1864 the hourly observations made 
at Bombay were published zz ex¢emso, and these twenty- 
four years’ hourly observations furnish data for the prose- 
cution of many inquiries, the value of which it would be 
difficult to over-estimate. From 1865 to 1872 the indi- 
vidual observations ceased to be published, but the hourly 
means for the different elements continued to be pub- 
lished. From these the hourly means of pressure, tem- 
perature, humidity, cloud, thunderstorms, &c., can be 
obtained for a period of more than thirty years. From 
the beginning of 1873, however, no hourly observations, 
or even hourly means, appear in the reports, want of 
funds presumably being the cause of the omission.  Irre- 
spective altogether of the length of time over which the 
observations have been made and the immense value this 
single consideration gives to the Bombay observations, 
the position of this observatory with respect to the 
monsoons and other vital elements of the meteorology 
of India render the maintenance of a first-class meteoro- 
logical observatory in this part of the empire indispens- 
able. It is in truth simply necessary in the interests of 
Indian meteorology and its satisfactory development that 
the Bombay Observatory be kept in a state of high 
efficiency, and that the individual observations made 
there be published and distributed among men of science 
at least as liberally as they were previous to 1865. 
OUR BOOK SHELF 
Supplement to “ Euclid and His Modern Rivals,’ con- 
taining a Notice of Henrici’s Geometry, together with 
Selections from the Reviews. (London: Macmillan 
and Co., 1885.) 
WE noticed the original work at such length in these 
columns (NATURE, vol. xx. p. 240), that it is not worth 
while on the present occasion to do more than draw 
attention to the issue of this “ Supplement.” 
Prof. Henrici’s “Congruent Figures” was published 
nearly contemporaneously with Mr. Dodgson’s book, and 
so he was unable to discuss the methods employed by the 
Professor, who, in the words of the present preface, “ fills 
the 7vé/e of that popular functionary, dear to Parisian 
diners, /e guatorziéme.” 
The discussion forms scene vi. of Act ii., and is headed 
“Treatment of Parallels by Revolving Lines,” and an 
extract, as usual, leads the way from Henrici’s Art 
of Dining (so our humourist puts it), viz. “in order that 
an aggregate of elements may be called a spread, it is 
necessary that they follow continuously.” 
It will thus readily appear to the readers of the 
“Euclid and his Modern Rivals,” or of our account 
referred to above—which by the way is honoured by a 
partial reproduction amongst the review-selections—that 
Mr. Dodgson is still himself, and that his hand has lost 
none of its former cunning. We should have liked him 
to have given his opinions on other parts of the Pro- 
fessor’s book, but it has not seemed good to the author 
so to act, and he has confined himself mainly, if not 
entirely, to the Lobatschewky treatment of parallels. 
With two such combatants now fairly in the arena, we 
shall be content to act as a mere onlooker whilst the 
strife wages fiercely between them, eagerly noting the 
parry and the thrust, and ready, if need be, to use the 
sponge as this or that combatant is struck. 
NATURE 
171 
It might be a mighty pretty encounter—Modern 
Treatment versus the Euclidian. 
Mr. Dodgson inserts remarks here and there in the 
text of the reprinted criticisms: he does not notice that a 
complaint he makes against us was in great part apolo- 
gised for on p. 404 (vol. xx., see above). 
Leitfaden bei zoologisch-zootomischen Prapaririibungen. 
Von A. Mojsisovics Edlen von Mojsvdr. 2nd ed. 
(Leipzig, 1885.) 
WE are glad to welcome a second edition of this work, 
which is a very useful manual for museum curators and 
for demonstrators in the rapidly increasing number of 
zootomical laboratories. Although it appears to be 
designed for use in high schools we cannot think that it 
is likely to displace the manuals already in use in this 
country : it wants the didactic character of Huxley and 
Martin’s “ Elementary Biology,” the simplicity and direct- 
ness of Prof. Milnes Marshall’s admirable little book on 
the “Frog” (which is, we are glad to learn, to be soon 
followed by others), or the detailed directions of Prof. 
T. J. Parker’s “ Zootomy.” We may note by the way that 
these works appear to be unknown to our author, whose 
knowledge, indeed, of English works on anatomy, or, as 
Messrs. Wilder and Gage call it, anatomical technology, 
is very incomplete. 
So far as German authorities on “ Museologie” are 
concerned, the second edition appears to have been 
brought up to date ; some additions, not always, however, 
improvements, have been made in the illustrations ; some 
of the English authors whose works are neglected would 
have provided the author with a better figure of As¢vo- 
pecien than the shocking “representation ” which is copied 
from Bronn. When the third edition is called for we hope 
we shall find the grave, but perhaps the only important, 
| defect which we have noted corrected and accounted for. 
LETTERS TO THE EDITOR 
[Zhe 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. 
No notice ts taken of anonymous communications, 
[The Editor urgently requests correspondents to keep their letters 
as short as possible, The pressure on his space ts so great 
that tt ts impossible otherwise to insure the appearance even 
of communications containing interesting and novel facts.] 
On Watering the Coal-Dust in Mines 
REFERRING to an explosion that happened at Lievin Colliery 
in the Pas de Calais on January 14 last, my friend M. Ed. 
Sauvage, Ingénieur des Mines, writes as follows :—‘‘Some 
experiments have been lately made at Lievin Colliery (Pas de 
Calais), where a disastrous accident happened a few months 
ago. Ido not think any report of these experiments has been 
published ; but they found the coal-dust inflammable, and the 
watering of the ways in the mine has been resorted to as a pre- 
caution against future accidents.” 
Twenty-nine persons were killed by this accident, that is to say, 
all who were in the mine with the exception ofone. The survivor, 
a miner named Cornet, and one of his comrades, had prepared a 
blasting-shot for dynamite, and called upon the shot-firer to 
ignite it. The latter examined the place, pronounced it to be 
free from fire-damp, and lighted the fuse. 
At the inquest Cornet stated that he saw the shot go off, and 
had just time, by a quick movement, to throw himself under a 
heap of straw lying near when the explosion took place. He 
remembered nothing more, and attributed his escape to the 
partial protection afforded by the straw. 
After investigating the case and hearing Cornet’s evidence, 
the Government engineer and those of the Company who owned 
the mine came to the conclusion that the explosion was caused 
by the ignition of the coal-dust that had been lying upon the 
timbers which formed the supports of the gallery. In corro- 
boration of this opinion they pointed out the fact that the current 
of air which swept through the gallery in which the explosion 
originated was too swift to admit of firedamp lodging there. 
