‘ ba ! 
* 
April 17, 1873] 
NATURE 
469 
which is drawn from them in directions other than that of 
their orbits. Schiaparelli maintains most distinctly that 
the tails of comets and meteoric aggregates are not 
identical. 
Professor Zéllner points out that if we are not to 
suppose that the physical constitution of both phenomena 
is the same, there only remains their identity of origin 
as an explanation of the remarkable coincidence of these 
bodies in space. Pursuing this argument and accepting 
its veracity, there is no reason to disbelieve the materials 
of which they are formed, to be the same. Schiaparelli 
supposes the nuclei of comets to consist of a solid sub- 
stance, which being subject to a kind of “ weathering pro- 
cess,” finally becomes broken up into separate pieces, 
which are turned into a meteoric swarm by the attraction 
and atmospheric resistance of a large planet. To this 
effect he again quotes Schiaparelli. Further on he ex- 
_ presses it as his opinion that comets and meteorites are 
the remains of planets, the former being their fluid and 
the latter their solid constituents. It must be left to 
future observers to decide whether the apparent disappear- 
ance of Biela’s comet has any connection with the rich 
fall of stars observed on November 27, last year. 
It is possible that the vapour left in consequence of the 
gradual evaporation of a comet would condense, in the 
absence of any powerful centre of attraction, into a num- 
ber of separate centres, as a cloud is dissolved into rain- 
drops on the increase of cold. In this way the condensed 
portions of cometary vapour would present the pheno- 
menon of numerous shooting stars as they penetrate the 
aos atmosphere in a solid or perhaps still fluid con- 
ition. 
PHYSICO-CHEMICAL RESEARCHES ON THE 
AQUATIC ARTICULATA* 
i N NATUuRE, vol. iv. p. 245, we gave a brief notice of some 
investigations M. Plateau had been making on the 
above subject. Since that time he has been continuing 
his researches in the same direction, and sends us an 
abstract of the results so far as concerns three problems 
in the life of aquatic Articulata. 
I, Experiments to ascertain the length of time that 
aquatic insects can remain under water without coming 
to the surface to breathe. 
The swimming aquatic Articulata which breathe air 
come frequently to the surface to renew their supply. The 
questions, How long may they with impunity remain sub- 
merged? what is their power of resisting asphyxia, as 
compared with that of terrestrial insects? are answered 
by the following experiments. At the bottom of an open 
vessel, of one litre capacity, full of ordinary fresh water, 
is placed a very small vessel, containing about 200 cubic 
centimetres. A piece of cotton netting so covers the 
mouth of the latter, that an insect, placed in the small 
vessel, is in reality in the general mass of the water, but 
cannot ascend to the surface. Terrestrial insects placed 
in these conditions, impelled by their specific lightness, 
rise to the lower surface of the network ; the movements 
of their legs soon cease, they do not appear to suffer, 
and they quickly grow torpid. The Coleoptera and aquatic 
Hemiptera, on the contrary, instead of submitting pas- 
sively to their fate, endeavour to quit their prison, swim 
rapidly about, exert themselves to come to the surface, 
and keep struggling until their strength is enfeebled, and 
end by lying at the bottom as if dead. 
In order to recover from its state of general torpidity 
an insect which has been submitted to prolonged immer- 
sion, it is necessary, after having taken it out of the water, 
to place it upon absorbing paper. If the time of its 
immersion has not passed a certain limit, the animal 
gradually recovers its energy, retaining no sensible 
* By M. Felix Plateau, 
trace of the experiment to which it has been submitted. 
M. Plateau repeated the experiment upon many indi- 
viduals and for various lengths of time, for the purpose of 
discovering, in the case of each species, the limit of time 
beyond which immersion caused the death of the insect. 
He arrived at two curious conclusions, supported by a 
great number of trials :— 
1. The terrestrial Coleoptera recovered from complete 
submersion continued for a very long time, in several 
cases for 96 hours. 2. The aquatic swimming Coleoptera 
and Hemiptera, far from presenting a greater resistance to 
asphyxia by submersion than the terrestrial insects, in 
most cases succumbed very much sooner. 
The cause of this unexpected inferiority in the case of 
the aquatic insects M. Plateau thinks is due exclusively 
to their greater activity in the water, causing as a conse- 
quence a more rapid loss of oxygen. 
II. Influence of Cold: Effects of Freezing. 
The results of M. Plateau’s experiments in this direc- 
tion are that the aquatic Articulata of the latitudes of 
Belgium exist for an indefinite period in water maintained 
at zero (centigrade) by means of melting ice ; while they 
cannot remain alive in ice for any length of time—not for 
half an hour at the utmost. The latter phenomenon ap- 
pears to be accounted for by the fact that the insects are 
completely deprived of all power of motion, thereby 
losing completely their animal heat. 
III. Action of Heat. 
Under this head M. Plateau tries to show the maximum 
temperature of water in which fresh-water Arachnoids can 
live. He finds that the highest temperature they can 
endure without injury oscillates between 33°°5 and 46°2 
centigrade. Comparing these results with those which 
have been obtained by experimenting with animals be- 
longing to other groups, M. Plateau finds that the greatest 
temperature which aquatic vertebrata, articulata, and 
molluscs can support probably does not exceed 46° centi- 
grade. 
NOTES 
WE have received a communication from Dr. Rein, Director 
of the Lenckenberg Society of Naturalists at Frankfort, which 
amusingly illustrates the perils that accompany the honours of 
the translation into a foreign language of a scientific work. 
Our informant relates that the well-known publisher, M. R. 
Oppenheim, of Berlin, having recently obtained the sanction of 
Mr. Poulett Scrope for the publication of a German translation 
of his work on ‘‘ Volcanoes,” of which a new issue lately ap- 
peared in this country, confided the work of translation to 
Prof. G. A. von Kléden, who accordingly performed the task. 
The translation was printed, together with a preface written by 
M. von Kléden himself—which preface, in the hurry of business, 
and in reliance, of course, on the good faith of the translator, 
the publisher forebore from examining. The volume in due 
course appeared, and was circulated by the publisher ; and not 
till then was it discovered that the preface aforesaid consisted of 
a severe and indeed bitter critique of the work to which it was 
prefixed, and of the author’s views as therein stated of the 
theory of volcanic energy, and its external development in the 
formation of cones and craters, &c. The explanation is that 
Prof. yon Kléden happens—unluckily for the author whose work 
he undertook to translate—to have been all his life an earnest 
advocate and teacher of the famous ‘‘Erhebungs-Krater,” or 
‘upheaval crater” theory of Humboldt and Von Buch, which 
Mr. Scrope, together with Sir C. Lyell, Constant Prevost, and 
other geologists have persistently opposed, and are, we believe, 
generally considered to have satisfactorily refuted. Of course it is 
open to Prof. von. Kléden to expound and defend his own opinion 
on this subject to the fullest extent in any independent publication ; 
but it does seem to be stretching the liberty of free expression on 
