308 
——— en 
Whether he is justified in classing the freshwater labyrintho- 
donts as marine fish-destroyers may be open to question; and 
his statement that the American Devonian fish Dinicthys occurs 
in the English ‘Old Red” does not appear to rest on good 
foundation. Why he should say that plesiosaurs ‘‘ condénued to 
the Mesozoic” is hard to understand ; and his estimate of the 
size of the dinosaurian Atlantosaurus (100 feet long and 30 feet 
high) appears a gross exaggeration. 
To the Motes from the Leyden Museum Dr. R. Horst con- 
tributes some remarks on the habits of the cocoanut-crab, based 
upon observations made on captive specimens at Batavia and 
living examples near Bantam by Mr. C. P. Sluiter. Recently 
some doubts have been expressed as to whether it is in the habit 
of ascending palm-trees. Mr. Sluiter has, however, seen these 
crabs climbto the top of mangrove-trees and palms fully 60 feet 
in height. What they did when at the top he was unable to 
ascertain, but, from observations made on captive specimens, he 
considers it probable that they were engaged in opening young 
cocoa-nuts and devouring their contents. Whether they have 
the power of opening ripe cocoanuts could not be determined, 
the specimens under observation merely fumbling such as were 
given them without attempting to penetrate the shell. 
Ar the conclusion of a memoir on the structure of the retina 
of the eye, published in the Quarterly Journal of Microscopical 
Science for July, Mr. H. M. Bernard states that this structure 
can no longer be regarded as being built up of a number of dis- 
tinct cells, each of which possesses distinct and definite functions. 
On the contrary, if distinct cells ever exist, their walls must be 
broken down at a very early stage of development. In technical 
terms, the retina is a continuous cytoplasmic reticulum containing 
non-stationary embedded nuclei. The other papers in the same 
serial include one by Mr. H. J. Fleure on the relations of the 
kidneys in Haliotis, and a second, by Miss I. Drummond, on the 
development of Paludina. 
IN most seismographs, the records are made on a sheet of 
glass or strip of paper which is either set in motion by an 
earthquake or has an ordinarily slow velocity increased at a 
somewhat advanced phase of the shock. In either case the 
interesting preliminary tremors are more or less completely 
lost. During the last three years, however, Dr. Cancani has 
avoided this loss by keeping the strip of paper continuously 
moving at the rate of six metres an hour. This velocity he has 
shown to be sufficient to decipher vibrations with a period of 
one-twentieth of a second and therefore above the lower limit 
of audibility. Ina paper recently published (o/?. Soc. Sésmol. 
Ttal., vol. vii. pp. 292-298), he maintains that even this velo- 
city may be conveniently increased to one ten times as great 
and therefore capable, so far as speed is concerned, of regis- 
tering the vibrations of earthquake-sounds occurring at the 
rate of 200 per second. 
A worTHy notice of the life and scientific work of the late 
Prof. P. G. Tait is contributed to the Physzcal Review (July) 
by Mr. A. Macfarlane, and is accompanied by a portrait of 
Tait printed in photogravure on plate paper. 
Messrs. Crospy Lockwoop AND SON have ready for 
publication a volume entitled ‘‘Aérial Navigation,” by Mr. 
Frederick Walker, dealing with the construction of dirigible 
balloons and other flying-machines; and another on the 
‘«Blements of Agricultural Geology,” by Mr. P. McConnell. 
In the abstract of the paper on refractive indices by 
Mr. J. W. Gifford, published in NATURE of July 17 (p. 287), 
line 12 reads, ‘‘ The difference of the angles of the prisms from 
60° were in each case /ess than 4 seconds of arc.” Mr, Gifford 
nforms us he should have said, ‘‘/ess than 4 minutes of arc.” 
No. 1708, VOL. 66] 
NATURE 
[JuLy 24, 1902 
AN interesting essay on ‘Clouds and Weather Signs,” by 
Commander D. Wilson-Barker, has been reprinted from Anow- 
Zedge and issued as an illustrated brochure. The pictures of 
clouds which the publication contains are exceptionally fine, 
and the descriptions of them should be the means of increasing 
the number of scientific observers of cloud phenomena. 
In the article on ‘‘Some New Forms of Geodetical Instru- 
ments ” which appeared in last week’s NATURE, it should have 
been mentioned that the illustrations of the instruments were 
from Sir Howard Grubb's paper in the Zvamsactions of the 
Royal Dublin Society (vol. vii. No. 15). We are indebted to 
the Society for the use of the illustrations. 
THE firm of Gustav Fischer, Jena, has begun the publication, 
exploration entitled ‘‘Aus den Tiefen des Weltmeeres,” by 
Prof. C. Chun. Although the original volume was remarkable 
for the large number of interesting and beautiful pictures, the 
second edition will contain many new illustrations. The work 
is one of five which are used as the text for an interesting 
essay on the methods and results of deep-sea investigations, in 
the current number of the Quarterly Review. 
AN excellent series of lecture experiments illustrating dif- 
ferent types of catalytic reactions is described by Messrs. Noyes 
and Sammet in vol. xli. of the Zeitschrift fiir phystkalische 
Chemie (pp. 11-27). For convenience, catalysators are divided 
into seven classes, namely, carriers, absorbent contact-sub- 
stances, electrolytic contact-substances, water, dissolved electro- 
lytes, enzymes and inorganic colloid substances, and by means 
of the simple experiments described, the catalytic function of 
substances belonging to any one of these classes in increasing 
the velocity of chemical change can be demonstrated to an 
audience in a very satisfactory manner. 
AN investigation of the rate of hydrolysis of sulphonic acid 
esters, published by R. Wegscheider in vol. xli. of the Zeztschrift 
fiir phystkalische Chemie, has shown that this phenomenon is 
very different in character from that observed with the ordinary 
carboxylic esters. Whilst the latter are hydrolysed much more 
rapidly by solutions of acids than by pure water, the hydrogen 
ion of the acids being supposed to act asa catalytic agent, the 
hydrolysis of sulphonic acid esters is scarcely accelerated at all 
by acids. A further study of this subject would no doubt afford 
valuable information with regard to the essential difference be- 
tween these two classes of acids. 
To the numerous syntheses effected by means of the mag- 
nesium alkyl halogen compounds is to be added an extremely 
elegant method of passing up the series of carboxylic acids. 
Messrs. Houben and Kesselkaul, in the current number of the 
Berichte, describe the synthesis of carboxylic acids by means of 
the action of carbon dioxide upon these magnesium compounds. 
Thus, as an example, ethyl bromide is treated with magnesium 
in the usual way and a slow stream of carbon dioxide passed 
in; propionic acid is easily isolated from the product in a yield 
corresponding to 50 per cent. of the theoretical. Acetic, pro- 
pionic, benzoic and phenylacetic acids have been synthesised in 
this way, so that the generality of the method is well 
established. 
Ar the Municipal Observatory of Montsouris the quantitative 
examination of atmospheric air has been carried out for a period 
of twenty-five years, About six years ago some special researches 
were commenced, under the direction of M. Albert Levy, by 
_ MM. Henriet and Pécoul, the first results of which were pre- 
sented to the Academy of Sciences in 1898. The fact was 
| announced that atmospheric air which had been perfectly freed 
from carbon dioxide by an exhaustive treatment with potash and 
in parts, of a new edition of the attractive work on deep-sea ; 
