304 
servation of these bodies, for he and others were of the 
opinion that these faint shooting stars were at vastly 
greater distances than those visible to the naked eye, 
for their slowness of movement and diminutive size 
suggested such remoteness. While ordinary meteors 
rarely become visible at a greater height than about 
too miles, these telescopic objects require distances of 
1000 to nearly 2000 miles to explain their appearance 
assuming as standard the ordinary velocity and length 
of flight of naked-eye meteors. From four objects 
Mr. Denning: inferred heights of 1260 to 1820 miles, 
and these he states were ‘‘only examples of a class 
and not rarities... The whole question is interest- 
ingly summarised in this contribution, and the author 
describes in detail observations extending over the 
period 1881 to 1902, and reproduces numerous dia- 
grams of various forms of trails observed. 
A New PuHotoGraPHiIc CHART OF THE Moon.—In the 
April number of L’Astronomie, M. Camille Flam- 
marion gives an account of the new photographic 
chart of the moon, which has recently been prepared 
by M. C. Le Morvan. M. Le Morvan during the last 
eighteen years has been associated with the production 
of all the plates for the great atlas of Loewy and 
Puiseux, and this important and unique collection of 
clichés, taken with the Paris equatorial coudé, pro- 
vides him with a rich assortment of material. The 
object of the work is to provide in a more convenient 
form as perfect a representation of the lunar surface 
as is possible in every detail. The plates are repro- 
duced in héliogravure, and are issued in two parts, 
each part consisting of twenty-four sections, and re- 
presenting increasing and decreasing phases respec- 
tively. The publication of this chart is rendered pos- 
sible by a grant of 4ooo francs out of the Bonaparte 
funds by the Académie des Sciences. M. Le Morvan 
communicates also a brief account of the construction 
of lunar charts. 
THE ROYAL SOCIETY .CONVERSAZIONE. 
HE annual May conversazione of the Royal 
Society was held on Wednesday, May 13, and 
was, as usual, largely attended. During the evening 
demonstrations were given in the meeting-room by 
Prof. J. P. Hill and Mr. P. Schilowsky. Prof. Hill 
gave a short account of the work of the Percy Sladen 
Expedition to Brazil, 1913, illustrated by lantern- 
slides of material collected and regions visited; and 
Mr. Schilowsky demonstrated the application of gyro- 
scopes to locomotion on land, on sea, and in air. 
The gyroscope’s stabilising property can be applied to 
unstable bodies like monorail cars or monotrack auto- 
mobiles, making them stable; that property can be 
used for stable but oscillatory bodies like ships, sub- 
marines, flving machines, preventing their rolling 
movement and rendering them perfectly steady. A 
description of the application of the system to a two- 
wheeled motor-car appeared in. Nature of May 7 
(p. 251). Dr. J. G. Gray exhibited gyrostats with 
accessories for showing the more obvious properties 
of the gyrostat, and a series of what may be called 
‘“animated’’ gyrostats. The latter consist of gyro- 
static acrobats, bicycle riders, and gyrostatic motor- 
cars, both two-wheeled and four-wheeled. A two- 
wheeled car was provided with a _ gyrostatic 
‘“‘chauffeur,’’ which stabilised the car and presided 
at the steering wheel. This car illustrated the action 
of directing and stabilising apparatus for use on tor- 
pedoes, airships, and aeroplanes. A further form of 
two-wheeled car demonstrated methods of stabilising 
and manceuvring an airship by means of forces derived 
from the propellers, which apply a direct push to the 
moving body. Dr. Gray’s bicycles and motor-cars 
NO, 2325; VOL. .o2i 
NATURE 
[May 21, 1914 
can be steered by the wireless transmission of elec- 
trical action. There were many other exhibits of © 
objects and devices of scientific interest, and we give 
descriptions, from the official catalogue, of some of 
the most interesting grouped according to related 
subjects. 
The Astronomer Royal: Transparencies of the 
Milky Way (selected from the Franklin-Adams chart). 
The whole sky was photographed on 206 plates by. 
the late J. Franklin-Adams. The plates have been 
presented to the Royal Observatory, and the number 
of stars of different magnitudes from the 12th to the 
17th have been determined. There are altogether 
fifty-five million stars on the plates, and from the 
sequence of the numbers for different magnitudes it 
is shown (S. Chapman and P. J. Melotte, Mem. 
R.A.S., vol. lx.), that the total number of stars in the 
sky is not less than 1000 millions, and cannot much 
exceed twice this amount, and that half the stars are 
brighter than the 23rd or 24th magnitude. Mr. 
George H. Cobb: A terrestrial globe, dated 1620, 
constructed to serve as a timepiece; supported by a 
gilt bronze figure of Atlas. Inside the globe is a 
movement of the verge type, so geared to the axial 
spindle that the globe revolves once in twenty-four 
hours. 
The National Physical Laboratory (Mr. F. E. 
Smith): Photographic record of the variations in the 
horizontal intensity of the earth’s magnetic field at 
the National Physical Laboratory. The record shows 
the variations in H from 1 p.m. on Saturday, April 109, 
to II a.m. on Sunday, April 20. The time scale 
(abscissa) is 43 cm. to the hour (7 mm. to the minute), 
and the intensity scale (ordinate) is 2-5 mm. for 2 
change in H of ty (o-oooo01 c.g.s. unit). The sudden 
variations are principally due to the earth currents 
produced by the London United Electric Tramway 
system. These sudden changes are not in general 
greater than 5y. Mr. W. A. Douglas Rudge: Electri- 
fication produced during the raising of a cloud of 
dust. During the raising of a cloud of dust by almost 
any method, considerable charges of electricity are 
produced. A charge of one sign is found upon the 
dust itself, and another charge of opposite sign, either 
upon the air, or else upon fine particles of dust which 
remain suspended in the air. Generally, dust of an 
acidic nature, such as silica or molybdic acid, give a 
negative charge to the air, metallic oxides and organic 
bases give positive charges to the air. 
Dr. J. A. Fleming: An apparatus for the production 
of stationary vibrations on strings, loaded and un- 
loaded. Various arrangements have been employed 
for the production of stationary vibrations on strings 
to illustrate the laws of wave motion. The apparatus 
exhibited consists of an electric motor having on one 
end of its shaft a counting mechanism, and on the 
other a disc to which is fixed a pin carrying the end 
of a rocking lever. This fever has on it a hook to 
which a string can be attached. The other end of 
the string is fixed to a slide rest arrangement, by 
means of which any required tension can be put on 
the string. When the motor revolves it gives to one 
end of the string an irrotational motion in a circle 
and propagates waves along the string. Bv adjusting 
the tension these waves can be made stationary. By 
employing a cotton cord, either single or multiple, 
in various degrees, it is easy to prove the fundamental 
laws of wave motion along cords. By using strings 
loaded with glass beads the effects of reflection at 
loads, or the laws of vibration of loaded cords, can be 
shown. Mr. W. Duddell: Water model of the electric 
arc. One of the essential properties of the electric arc 
is that, when the current through the arc increases, 
the potential difference between its terminals de- 
creases. The model exhibited consists of a mushroom 
