344 
NATURE 
through a friction-roller from a clock furnished with a 
centrifugal governor, acting by fluid-friction, and balanced 
so that its speed is not sensibly affected by the shaking of 
the ground. The clock is started into motion by means 
of a Palmieri seismoscope, which appears in the figure 
behind the plate, on the right. This is a small common 
pendulum whose bob carries at the bottom a piece of 
stiff platinum wire that projects into a recess ina cup of 
mercury below—the recess being formed by an iron pin 
standing lower than the surface of the surrounding mer- 
cury. On the slightest shaking of the ground, contact 
with the edge of the mercury takes place, and this closes 
a circuit which releases an electro-magnetic detent and 
starts the clock. This occurs during the preliminary 
tremors which are usually found in advance of the main 
movements of an earthquake. The same circuit starts 
another clock (of the escapement type) which fulfils 
two functions. It marks time on the revolving plate 
during a part of the first revolution, and then continues 
to go as an ordinary clock, so that, by inspecting its dial 
afterwards, the interval which has elapsed from the oc- 
currence of the earthquake is known, and the date of the 
shock in hours and minutes is thus determined with as 
much precision as the phenomenon admits of. This part 
of the apparatus is omitted from the figure. The two 
horizontal components of motion are recorded by a 
pair of horizontal pendulums, set at right angles to 
each other, but with their indices inclined so that they 
write side by side on one radius of the plate. The pen- 
culums are supported on a single stand, but with inde- 
pendent adjustments for position and stability. Each has 
two pivots, consisting of hard steel points, which turn in 
sapphire centres. At the pivots and at the tracing-points 
every effort has been made to avoid friction. The indices 
are of aluminium, and a part of their weight is taken by 
springs (not shown in the figure), so that their pressure 
on the plate may be no greater than is necessary to pro- 
duce a trace on the sooty film. The vertical component 
of motion is recorded by the instrument which appears 
behind the clock. A massive bar, free to move vertically 
about a horizontal axis, is held up by a pair of long spiral 
springs. Its equilibrium is made nearly neutral by ap- 
plying the pull of the springs at a suitable distance below 
the horizontal plane through the axis of support, in the 
manner described in the article to which reference has 
already been made. A bell-crank lever with a jointed 
index gives a multiplied trace of the apparent vertical 
oscillations of the bar, which correspond to vertical dis- 
placements of the ground. In this instrument, as in the 
others, sapphire centres are used to minimise friction. 
Records inscribed on the plate are preserved by var- 
nishing the plate, and using it as a “negative” to print 
photographs. The motion, as recorded, is magnified to 
an extent which experience of Japanese earthquakes has 
shown to be desirable in dealing with disturbances ranging 
from those which are just recognisable as earthquakes up 
to those which are to some extent destructive. For great 
earthquakes, separate apparatus of the same type is de- 
signed, in which the multiplying indices are dispensed 
with, and the scale and style of the other parts are con- 
siderably modified. 
Another and distinct instrument, also manufactured by 
the Cambridge Company, is the duplex pendulum seismo- 
graph, shown in Fig. 2. A massive bob is hung by three 
parallel wires from the top of a three-cornered box, and is 
reduced to nearly neutral equilibrium by being coupled by 
a ball-and-tube joint to the bob of an inverted pendulum 
below it. The two form a system which can be made as 
nearly astatic as is desirable, and so furnish a suitable 
steady-point for the horizontal part of earthquake move- 
ment in any azimuth. The motion is magnified and 
recorded by a vertical lever geared to the upper bob by a 
ball-and-tube joint, supported on gimbals from a bracket 
fixed to the box, and furnished with a jointed index 
[August 12, 1886 
which writes on a fixed plate of smoked glass. Records 
of the kind which the duplex pendulum gives are of 
course incomplete in two important particulars: they 
show nothing of the vertical motion (which, however, is 
usually a comparatively small part of the whole), and 
they show nothing of the relation of ¢me to displace- 
ment throughout the disturbance. But they exhibit very 
clearly the change of direction which the movements 
undergo, and the actual direction taken by any pro- 
nounced element of the shock. The writer has recently 
learnt from his former assistant, Mr. Sekiya, now Pro- 
fessor of Seismology in the University of Tokio, that as 
many as fifteen of the duplex pendulum seismographs 
are in use by official and private observers in Japan. 
The instrument shown in the figures are now on view 
at the Edinburgh International Exhibition (Court 21, 
No. 917). Similar sets are being made for the Lick 
Observatory, California, the Ben Nevis Observatory, and 
other places. It is scarcely necessary to add that they 
show the high finish and perfection of workmanship 
characteristic of the Cambridge Company’s manufactures. 
To Mr. Horace Darwin the writer is especially indebted 
for a number of suggestions the adoption of which has 
contributed much to scientific accuracy in details and 
simplicity in structural arrangements. 
J. A. EWING 
THE INSTITUTION OF NAVAL ARCHITECTS 
AT LIVERPOOL 
HE Institution of Naval Architects departed this year 
from their almost invariable custom of holding 
meetings in London, and had a most successful series of 
meetings at Liverpool. The papers read were few in num- 
ber, but they were of special, and, in some cases, unusual 
interest. The meetings were attended by a large number 
of the Members of the Institution, as well as Liverpool 
scientific men, shipowners, underwriters, engineers, and 
others interested in the subjects of discussion. A local 
paper was read by Mr. G. F. Lyster, C E., the Engineer 
to the Mersey Dock and Harbour Board, upon the Docks 
of Liverpool; Prof. F. Elgar read a paper upon “ Losses 
of Life at Sea”; Mr. B, Martell upon “The Carriage of 
Petroleum in Bulk on Over-sea Voyages’’; Mr. W. John 
upon “ Atlantic Steamers”; and Mr. W. Parker on the 
“ Progress and Development of Marine Engineering.” 
Prof. Elgar’s paper upon losses at sea has attracted much 
attention. It contains a general analysis of the losses 
that happened during the triennial period that has 
recently caused so much controversy as to whether loss 
of life at sea is increasing or not, viz. the three years 
1881-83. Details are given, in a set of tables appended to 
the paper, of the steamers and iron sailing ships belonging 
to the United Kingdom, of and above 300 tons gross 
register, that were reported to the Board of Trade as 
foundered or missing during the five calendar years 
1881-85.. The facts contained in these tables show clearly 
the great advantage it would be to the shipping com- 
munity if such information were published periodically 
in a clear and convenient form. Probably no docu- 
ments that emanate from any Government Department 
are more bewildering, or more difficult to extract any 
tangible information from, than the voluminous and com- 
plicated returns of wrecks and casualties, and of lives lost 
at sea, that are published annually by the Board of Trade. 
We hope that the attention of the Royal Commission 
now sitting upon Less of Life at Sea, has been forcibly 
directed to the many imperfections and the comparative 
uselessness of the present published returns that profess to 
deal with these matters ; and that one of the Committee’s 
recommendations will be that something should be done 
to make them clear and instructive. 
There is another cognate matter which we hope will also 
be dealt with satisfactorily by the Royal Commission, viz. 
a eee 
