230 
NATURE 
[JuLy 6, 1899 
the balloons were electrically charged. The details of the in- 
vestigation were published in the Sztzwngsberichte of the Vienna 
Academy in March last. 3 
So many attempts have been made to produce photographic 
pictures in natural colours, that a bibliography of recent contri- 
butions to the subject is distinctly valuable. Mr. Philip E. B. 
Jourdain gives such a bibliography in Photography of June 22. 
His paper supplements similar bibliographies prepared by Mr. 
Bolas, the chief additions being a fuller account of Edmond 
Becquerel’s work, and abstracts of two important papers by 
Clerk Maxwell and Lord Rayleigh on different branches of the 
subject. A number of processes, in addition to those known to 
most men of science, are described. The bibliography carries 
the subject to the end of 1898, so Mr. R. W. Wood’s process 
(see p. I19) is not included. 
THE property that the locus of the poles of an arbitrary plane 
with respect to the conics of a Steiner’s surface is another 
Steiner’s surface has been investigated by Lie, Koenigs, and 
Brambilla. In a communication to the fRezdéconto of the 
Naples Academy (v. 4), Prof. Domenico Montesano has dealt 
with the following questions connected with this problem ;— 
(1) In what relation of position are the two surfaces? (2) 
Whether the relation is invertible? (3) What forms are de- 
scribed by the double lines, the triple point, and the double 
tangent planes of the new Steiner’s surface when the arbitrary 
plane is varied? In order to answer these questions, Prof. 
Montesano examines the correlative questions for the surface of 
the third order with four double points, making these depend 
on other more general questions relating to a surface of the third 
order without singularities. 
In the Bulletin tnternational of the Cracow Academy, M. P. 
Rudski applies the well-known problem of the elastic sphere 
under given surface-tractions to calculate the radial displace- 
ments of the earth’s surface under the weight of ice-caps. 
There are strong reasons for believing that during the glacial 
period large areas of land were submerged, which at the 
present time are at considerable altitudes above the sea-level, 
and M. Rudski’s object is to test whether these displace- 
ments of the shore-line can be accounted for by the dis- 
tortion of the earth due to circumpolar ice, assuming the total 
quantity of water on the earth’s surface to be constant. M. 
Rudski considers the test case of uniform ice-caps extending 
down to latitude 60°, and he assumes the rigidity of the earth to 
be the same as that of steel. The deformations are different 
according to whether glaciation exists about one or both poles, 
the depressions at the poles being respectively 347°1 and 497°8 
metres for an ice-cap 2000 metres thick. Moreover, with 
bipolar glaciation the displacement of the shore at the edge of 
the ice-caps is negative, while with unipolar glaciation it is 
positive but smaller. In either case, supposing fiords to extend 
inwards into the ice-caps, the shore-displacements towards the 
centre of the caps would be positive. 
Ir is well known that the influence of a magnetic field in 
general increases the electric resistance of the rarefied gases, 
except when the lines of electric and magnetic force coincide. 
Profs. Elster and Geitel, writing in the Verhandlungen of the 
German Physical Society, describe an experiment showing 
that a magnetic field has a similar effect on the conductivity im- 
parted to air by the influence of Becquerel rays. Experiments 
have also been made by the same writers, showing that the 
observed results were not attributable to any deviation produced 
in the rays by the magnet, but that Becquerel rays, like Rontgen 
rays, possess the property of not being deflected by magnetic 
force. 
NO. 1549, VOL. 60] 
In the last number of the Zertschr. Wass. Zool., Mr. L. Johann 
notices certain peculiar epidermal structures occurring at thé 
base of the spines of one of the spiny dog-fishes (Spinax niger), 
which he believes to be luminiferous. They take the form of 
brown or black spots, which are not shining, and are situated 
on a dark ground. Although distinctly visible to the naked 
eye, they are seen better through a lens; and, owing to the 
nature of the skin, are more clearly displayed in the embryo 
than in the adult. When sectionised and examined microscop- 
ically, they are found to contain pigment. A tropical repre- 
sentative of the same family (Zs¢s¢ius brasdliensis) is already 
known to possess luminiferous properties, and the author there- 
fore considers that the spots in the Mediterranean species have 
the same function, By a fortunate coincidence, as his paper 
was passing through the press, Mr. Johann received a com- 
munication from Dr. Beer, of the Zoological Station at Naples, 
Stating that a specimen of Sfznax niger had recently been 
captured and brought to the aquarium there. Although 
wounded and in a generally feeble condition, it emitted a 
distinct luminosity, which would doubtless have been stronger 
had the fish been in robust health. The author’s conclusions 
as to the function of the dermal spots are, therefore, demon- 
strated by actual experiment to be correct. 
STUDENTs of the Batrachians will be much interested to read 
in the Proc. U.S. Nat. Mus. Dr. Stejneger’s account of the dis- 
covery ofa North American representative of the family of disc- 
tongued frogs (Déescog/ossedae), hitherto supposed to be confined 
to the northern half of the Old World and New Zealand. The 
determination rests on a single specimen discovered in the 
western portion of Washington State, which is considered to 
belong to a new generic type (Ascaphus). 
THE July number of the Century Magazine contains an 
exceedingly well-written and well-illustrated article describing a 
rocky islet in the Gulf of St. Lawrence known as ‘‘ Bird Rock,” 
and now utilised as a lighthouse station. From the accounts of 
early visitors to the rock (among whom was Audubon) it 
appears that the number of sea-birds—such as gannets, guille- 
mots, puffins, razorbills and petrels, with which it was covered — 
was almost incredible, Dr. Bryant, who paid a visit in 1860, 
estimating the number of gannets alone at one hundred and fifty 
thousand. Although, to one who has not read the old accounts, 
the rock would even at the present day appear a marvellous 
example of the exuberance of bird-life, it is only too certain that 
unchecked plunder of the eggs and destruction of the adults are 
steadily tending towards the extermination of the feathered 
hosts. By all means, therefore, let the Government con- 
cerned forthwith take the simple steps suggested by the 
author as essential to ward .off the occurrence of such a dire 
calamity. : 
THE useful series of ‘‘ Manchester Museum Handbooks” has 
received an important addition in the form of an ‘‘ Index to the 
Systema Naturae of Linneus,’ by Mr. C. D. Sherborn. 
Needless to say, this work is executed with the thoroughness 
and care characterising all the efforts of its author. Whether, 
however, it will ‘“‘help in bringing about that uniformity of 
nomenclature which is the great need of zoological science at 
the present day,” the future alone will show. There may also 
be two opinions as to whether Linnzeus, the founder of our 
nomenclature, ‘‘had no more power to alter a name once 
founded than has any other person.”—The ‘‘Guide to the 
Natural History Collections” in the same series is so well 
written, and contains such a large amount of information in such 
a very small compass, that it will prove useful to many besides 
actual visitors to the museum. 
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