ON SEISMOLOGICAL INVESTIGATION. 225 
\ 
grammes, and magnifies five times the displacements of the lower end of 
the vertical lever. The rate of the smoked 
paper is increased to about 15 mm. a 
minute, a velocity which enables the pen- 
dular oscillations to be distinctly traced. 
Dr. G. Agamennone’s Seismometro- 
graph.—tThe latest form of this instrument 
is described in a paper, ‘Sopra un nuovo 
tipo di sismometrografo’ (‘ Boll. Soc. Sismol. 
Ttal.,’ vol. i. 1895, pp. 160-168). It was in- 
stalled at Rome about two years ago in 
the tower of the Collegio Romano. Owing 
to the difficulty of reproducing the illustra- 
tion of this pendulum, several of the details 
of construction are necessarily omitted in 
the following account :— 
The bob of the pendulum consists of six 
discs of lead, weighing altogether nearly 
200 kg. This heavy mass is suspended by 
an iron rod 7 or 8 mm. in diameter and 16 
metres in length, but to make the pendulum 
more sensitive the upper end of the rod is 
prolonged as a steel wire 2 or 3 mm. in 
diameter, and 50 or 60 cm. long. At the 
lower end the rod terminates in a smooth 
eylinder of steel of about the same thick- 
ness, passing through slits made in the 
short arms of two horizontal levers. These 
levers, which turn with very little friction, 
are mounted on a strong frame provided 
with screws for securing the verticality of 
the axes about which the levers rotate. The 
longer arms of the levers are about 35 cm. 
in length, being about twelve times as long 
as the short arms. They are triangular in 
form, and are made of very thin brass 
tubes. The levers are bent, so that while 
the short arms are at right angles to one 
another, pens at the ends of the long arms 
record the components of the movement on 
the same strip of moving paper. The pens 
are supplied with ink of different colours 
to avoid confusion of the records if the 
pens should happen to cross one another, 
In order to prevent the pens leaving the 
strip of paper, the movements of the pen- 
dulum are limited by four screws. A 
strong box is placed immediately below the 
heavy mass to save the instrument from 
further damage in case the steel wire 
should break. 
The strip of paper on which the pens 
record the movements of the pendulum is driven by a cylinder about 
1896. sisGine Q 
Fie. 15. 
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