456 
is necessary when the tellurous oxide is dissolved originally in an 
alkaline hydroxide and the solution made acid only to a limited 
degree with sulphuric acid.—An iodometric method for the esti- 
mation of boric acid, by L. C. Jones. The method is based 
upon the employment of mannite and of a mixture of potassium 
iodide and iodate.—A method for the detection and separation 
of dextro- and levo-rotatory crystals, by D. Albert Kreider. 
The method is based upon the use of a kind of polarimeter with 
a wide field of vision of a uniform colour, adjusted in such a 
manner that any small crystal instantly reveals the sense of its 
rotation by its colour when brought into the field.—New 
meteoric iron found near the Tombigbee River, Choctaw and 
Sumter Counties, Alabama, by W. M. Foote. The fall consisted 
of a series of pieces found in almost a straight line north and 
south along a nine-mile stretch of the public road.—Orthoclase 
crystals from Shinano, Japan, by C. Iwasaki. Describes four 
different classes of orthoclase, mostly twinned after the Baveno 
type. 
Wiedemann’s Annalen der Phystk und Chemie, No. 7.— 
Smallest thickness of liquid films, by K. T. Fischer. The 
author brings the widely varying results of various observers 
into approximate harmony by supposing that when a drop of 
oil is placed on a surface of pure water, a ‘‘ precursory film ” 
spreads over the water first, and is followed at a slower rate by 
the film studied by Sohncke and others. For his own experi- 
ments the author used a pure mercury surface, which he found 
to possess various advantages.—Wehnelt’s electrolytic inter- 
xupter, by A. Voller and B. Walter. The hydrogen lines are 
wery pronounced in the spectrum of the Wehneltspark. Intense 
and pure metallic spectra may be obtained by choosing the 
metal in question as the substance of the anode. The hvdrogen 
dines do not interfere, but serve as lines of reference.—Kathode 
rays, by A. Wehnelt. The author distinguishes between two 
‘classes of kathode ray shadows. One class is produced by rays 
emerging from the kathode normal to its surface and crossing 
each other at a focus in the case of a curved kathode. The 
other class consists always of upright shadows, thrown by rays 
travelling in a direction parallel to the axis of the tube. —Cause 
of the change in the conductivity of a metallic powder, by T. 
Sundorph. The author proves the formation of connecting 
chains of particles in a coherer by sparking across the gap 
between two metallic blocks on a glass plate, with a layer of 
nickel or iron filings between them.—A new vacuum discharge 
phenomenon, by L. Fomm. <A vacuum tube is surrounded by 
wire rings at its two ends. At a certain exhaustion blue rings 
appear, concentric with the wire rings, and enclosing patches of 
positive light, which gradually disappear until the blue light 
fills the whole cross section. As the pressure diminishes still 
further the blue light detaches itself from the glass walls, and 
expands longitudinally, forming a greenish-blue beam which 
proceeds in the direction of the other ring, and shows all the 
properties of kathode rays.—Some experiments with Wehnelt’s 
interrupter, by E. Lecher. The author describes some beautiful 
phenomena obtained by bringing the secondary spark discharge 
of a Wehnelt interrupter into a magnetic field. The secondary 
current is unidirectional, and is therefore deflected in a constant 
direction. When the discharge takes place between a circle of 
wire and a disc mounted in its plane, and concentric with it, the 
Alischarge consists of curved spokes of light which rotate rapidly, 
in a sense governed by the polarity of the magnet. The dis- 
-charges form a kind of fire-wheel as displayed in pyrotechnics. 
SOCIETIES AND ACADEMIES. 
PaRIs. 
Academy of Sciences, August 28.—M. Michel Lévy in 
the chair.—On the general form of the equations of dynamics, 
by M. P. Appell. The advantage of the form of equation de- 
scribed is that it allows the use of parameters which are not 
irue coordinates, but are connected with the coordinates by 
non-integrable differential relations. The method is of especial 
service in problems of rolling.—On the velocity of detonation 
of acetylene, by MM. Berthelot and Le Chatelier. Acetylene 
was detonated in a glass tube by caps of mercury fulminate or 
chlorate powder, care being taken to have the detonator as 
small as possible, as it was found that irregularities were intro- 
duced if the detonator used was too violent. The acetylene 
was contained in horizontal glass tubes, under pressures varying 
from 5 to 36 atmospheres, and the velocity was registered 
NO. 1558, VOL. 60] 
NATURE 
[SEPTEMBER 7, 1899 
photographically upon a falling sensitised plate, the light emitted 
by the explosion itself being sufficient for the purpose. As the 
flame moved further from the source of explosion the velocity 
continually increased, the tube generally breaking before the 
speed became uniform. Even when the conditions of in- 
flammation and pressure are apparently precisely identical in 
two succeeding experiments, discordant results were sometimes 
obtained for the increase of velocity of the flame along the 
tube. The results show that the propagation of the detonation 
of acetylene is produced with a velocity which increases with 
the pressure from 1000 metres per second at 5 atmospheres 
pressure to 1600 metres per second at 30 atmospheres.— 
M. Henri Moissan communicated to the Academy a letter 
he had received from Prof. Dewar, of London, in 
which details were given of the solidification of hydrogen. 
Solid hydrogen melts at 16° absolute (— 257°), and at this 
temperature helium is liquefied under a pressure of 8 atmo- 
spheres.—Discovery of a new planet at the Observatory of 
Paris, by M. Jean Mascart.—The Perseids in 1899, by M. C. 
Flammarion. The tabulated list is accompanied by a chart 
showing the point of origin and direction of motion of the 
Perseids in 1899 — On beats given by vibrating strings, by M. 
C. Maltézos. The ordinary equation for a thin elastic string 
giving the relation between the number of vibrations, tension, 
section, and length of string gives no explanation of the pheno- 
menon of beats. If the rigidity of the string be taken into 
account, the author theoretically deduces an expression for the 
number of vibrations from which can be deduced that the 
number of beats is proportional to the square root of the area of 
section, inversely proportional to the cube of the length, and 
inversely proportional to the square root of the tension. The 
last conclusion has, been verified experimentally, but instead of 
the number of beats being inversely proportional to the cube of 
the length of the strength, it is nearly inversely as the length 
simply. Hence it is impossible from rigidity alone to explain 
all the phenomena of beats in vibrating strings. 
CONTENTS. PAGE 
The Little Negroes of the East. By Prof. A. C. 
Haddon, FIR-S)) en. See eo OF 
Bacteria. By Dr. A.C. Eeneton PE oc joe ER 
Our Book Shelf :— 
Zoppritz: ‘‘Leitfaden der Kartenentwurfslehre.”— 
Sir C. W. Wilson, K.C.B., F.R.S. Ly at ene 
“« The Dog, its External and Internal Organisation” . 435 
Letters to the Editor :— 
A Hertz Wave Receiver. (With Diagram.)—Rev. 
FE. J; Jervis-Smithyekeeons.-), 7. «1;-sl lien meg 
Is Insusceptibility to Vaccine produced by Small- -pox ? 
—Charles G. Stuart-Menteath; Prof. G. 
Sims Woodhead ..... e480 
The Dover Meeting of the British Ascacinnee «2 4450 
The Forecast of the Monsoon .. . 438 
The Present Position of the faeatieation Gs the ; 
Malarial Parasite) pee; | > eee 
Notes: (Z//astraledi\yn pis). - e 
Our Astronomical Column :— 
Holmes’:Comet 1899@ (1892 III.) . ...... . 442 
The New Algol Variablein Cygnus .......-. 442 
Harvard College Observatory. . . . . . «++ = + 442 
Torsion-Structure in the Alps. (///ustrated.) . By 
Dr. Maria M, Ogilvie. .... Sic ces. 3 eae 443 
The Motion of a Perfect Liquia. (Zilustrated.) By 
Prof: 1H. S.HelesShiawaebe ease cis. o-0. Gneme 446 
A Problem in American Anthropology. By Prof. 
Frederic Ward Putnam... . Ro c.f CESS 
University and Educational iaeieence oe ES 
Scientific Serials.) (jp giewemeewei= 0 MEMS) 
Societies'and Academiesmssiene= « «>. « -memeEEa50 
