586 
NALURE 
[Aprit 18, 1907 
really grasped the all-important stability problem, or 
that the necessity of carefully studying the small 
oscillations of gliders, both stable and unstable, has 
been appreciated. It seems probable that a great 
many constructors of would-be flying machines do 
not even know what is meant by a moment of inertia, 
yet both theory and experiment tend to show that the 
stability of a machine depends partly on its moment 
of inertia being neither too large nor too small. 
The models exhibited are of various sizes, and 
adapted for propulsion through the air by means of 
twisted elastics, like the familiar toys; they are, how- 
ever, of various dimensions, say from about 3 feet 
to 6 feet. The trials which were made at the Alex- 
andra Palace on Monday thus involved none of the 
dangers attendant on experiments with man-carrying 
machines. It is to be hoped that some means were 
taken to record the actual motions of the models 
while in the air. Such a record, if made in a way 
that would enable the positions and the velocities of 
the models to be plotted at every instant of the 
motion, could be made to furnish material the study 
of which will greatly advance our knowledge of the 
flight problem. From what I learnt at the exhibi- 
tion, it appeared that this matter had not received 
much, if any, attention, but I was given to understand 
that two kinematographs would be employed to obtain 
the necessary records. The necessity for two is ob- 
vious, and I can only hope that the requisite measure- 
ments of base line and angles were also attended 
to. 
In the following remarks I shall assume the result 
that a machine supported on aéroplanes has two kinds 
of longitudinal oscillations of different period, either 
of which may give rise to instability. This is not 
generally known, but it is desirable to analyse the 
models even in the light of ideas which are to some 
extent anticipatory. The rough notes taken are far 
from exhaustive, but they summarise a few points 
regarding some of the more conspicuous exhibits. 
Ezio Tani shows a most elegant and beautifully 
constructed mechanism in connection with the motor; 
the arrangement of wings does not look very 
practicable. 
Balston and Cochrane both exhibit propellers, &c., 
of corrugated aluminium. 
The avroplane looks a fairly practicable model. 
The arrangement of two sets of planes tandem 
fashion appears suited for stability, at any rate so 
far as the short oscillation is concerned, but a great 
deal depends on whether the planes are parallel or 
inclined at a slight angle. On the other hand, the 
increased moment of inertia caused by the projecting 
framework and the considerable distance between the 
front and hind surfaces may give trouble with the 
long-period oscillation. 
The Drexler model seems to go to the other 
extreme, and suggests that the shortness of base may 
lead to trouble with the quick-period oscillation. 
Here the planes are superposed, not arranged tandem. 
Weiss’s albatross is really a model of a bird with 
curved* wings. How far this imitation of the shape 
of bird’s wings conduces to stability cannot be com- 
pletely studied without further experimental data than 
are at our disposal. The model looks as if it would 
glide well for a short distance, but without a very 
careful system of recording, short flights teach us but 
little. 
Montford Kay shows a model of great length 
with propeller placed in the middle of a number of 
long parallel aéroplanes. The arrangement seems ill- 
calculated for obtaining much lifting force from the 
air. 
Piffard with 
shows a reasonable form of model 
two pairs of superposed aérocurves, one behind the ! for this purpose. 
NO. 1955. VOL. 75] 
other. As arranged at the exhibition, the combin- 
ation looked as if it would be unstable for moderate 
velocities, but a slight change in the inclination of 
the aérocurves might make all the difference. 
T. W. K. Clark shows the most genuine attempt 
to cope with the problem of stability, he having 
followed the lines laid down by Chanute in the matter 
of flexible framework. From what I could gather, 
however, the necessary movements for balancing 
were not arranged to take effect automatically, but 
the machine was a small-sized model of a type in- 
tended to be balanced and controlled by the dexterity 
of an aéronaut. 
It would be impossible from these rough observ- 
ations to draw any very definite conclusions about the 
probable results of the competition, but it may be 
apposite to remark in conclusion that failures may 
teach aguite as much as successes if only they are 
properly studied. G. H. Bryan. 
THE STUDY OF EARTHOUAKES. 
HE Imperial Earthquake Investigation Com- 
mittee of Japan has supplemented its well- 
known Publications by a bulletin, issued with the 
object of securing a quiclx publication of short notes 
and preliminary reports on seismological subjects. 
The series opens with a very interesting number; 
there are papers on the determination of the time of 
origin of a distant earthquake, on the methods of 
calculating the velocities of earthquake propagation, 
on the Tokyo records of the Calabrian earthquake, 
and, most interesting of all, a discussion of the cause 
of the San Francisco earthquake, by Prof. Omori, 
who describes the great fault-fissure, referred to in 
Narure of June 21, 1906 (vol. Ixxiv.), and notices 
that near Pt. Arena and at some other places it did 
not show at the surface as a simple fault-fissure, but 
as a zone of distortion crossed by parallel shear- 
cracks, from the direction of which he concludes that, 
besides the relative displacement of the two sides of 
the fault zone, there was a general compression of 
the country from north to south. This displacement 
was no mere surface phenomenon, as it appeared in 
the tunnel near Wright station, some forty miles 
S.S.E. of San Francisco, at a depth of some 7oo feet 
from the surface. From the direction of overthrow 
of objects, Prof. Omori concludes that the whole of 
the country along the fault has been displaced to- 
wards the N.N.W., but the west side more than the 
east. 
In Austria the collection of earthquake statistics 
has been taken over from a committee of the Imperial 
Academy of Sciences by a newly extended Govern- 
ment. Institute of Meteorology and Geodynamics. 
The first of the seismological publications of this 
institute is a catalogue of the earthquakes of the 
Austrian Empire in 1904, which are detailed province 
by province, with the addition of a general summary. 
A catalogue of this sort is as important and useful 
as a collection of meteorological tables; it is little 
more interesting to read, but, if not pleasant read- 
ing in itself, this little pamphlet suggests some 
interesting if not very comforting considerations. 
The science of seismology is essentially an English 
one; it is to Englishmen, and practically to two of 
them, that. most of its fundamental concepts owe 
their origin; the ideas, which give vitality, and the 
terms which are in universal use, have almost all 
been born in this country, yet England remains with- 
out any permanent or official. organisation for the 
collection of earthquake information, while one 
country after another is establishing a special service 
Nor can the neglect be excused by 
