50 REPORTS ON THE STATE OF SCIENCE. 
The seismograph room is situated on the ground floor of the main 
office building. The principal pier is built of solid cubes of sandstone, 
and passes directly to the rock at a depth of 21 feet. The pier 
is enclosed in a brick well to isolate it from local surface movements. 
The Milne twin-boom instrument is mounted on this pier, so as to 
give N.S. and E.W. components. The period of the booms is about 
18 seconds, and at this period the scale is 1 mm. =0°’391. 
A spare pier is also situated in the room, and will be used for 
research work on the behaviour of other forms of seismographs. 
Toronto, Canada.—When the magnetometers, on account of inter- 
ference with electric trains, were moved from Toronto to Agincourt 
the seismograph was moved also. The underlying rocks at Agincourt 
are the same as those at Toronto, about nine miles distant. These are 
Hudson River shales, covered with a thick deposit of alluvium. These 
latter drift deposits no doubt differ to a certain degree, but there are 
no sections at Agincourt which can be compared with those at Toronto. 
It may be mentioned that when the magnetometers were in Toronto 
they did not appear to have been disturbed at the time of large earth- 
quakes. Now that these instruments are removed to Agincourt from 
time to time they show irregularities which may be due to teleseismic 
movement (see ‘ B. A. Reports,’ 1898, p. 237; 1899, p. 170). 
Porto Rico, W. Indies.—The instrument at this station is of the 
Bosch-Omori type and forms part of the equipment of the United States 
Coast and Geodetic Survey. It is established at the Magnetic Observa- 
tory situated on Vieques Island, east of the island of Porto Rico. It 
is mounted in the north-east. corner room on the ground floor of the 
old Spanish fort ‘ Isabel.’ The floor of the room consists of 3 inches 
of cement underlaid with 3 inches of hard clay, which in turn is under- 
laid by stone. The piers, four in number, on which the seismograph 
parts are mounted are each 20 inches square by 324 inches deep. Each 
consists of three pieces of dressed stone. These are laid in cement and 
extend 30 inches below floor-level; the space round each pier is filled 
with cement within 4 inches of the floor. The instrument consists of 
two pendulums recording north-south and east-west motion. It is 
possible to obtain the time of any effect within one or two seconds. 
The paper moves 15 mm. to the minute. The period of north-south 
pendulum is 26°36 seconds; east-west pendulum 24°7 seconds. The 
multiplication of the tracing points is 10. 
Stonyhurst, near Blackburn, North Lancashire, England.—The lati- 
tude of the observatory is 538° 50/ 40” N; longitude, 0° 52’ 68” W of 
Greenwich. The seismograph is the one which was used for two years 
in the Antarctic regions by the officers of the s.s. Discovery. The 
standard and other parts of the instrument are made of gunmetal and 
non-magnetic materials. At Stonyhurst it is installed in the under- 
ground magnetic chamber, which is dry and does not suffer from varia- 
tions of temperature. It is placed on a pillar composed of two cut 
stones firmly cemented together. On the top of these there is a slate 
slab also cemented to the uppermost stone. The pillar is embedded in 
and rests upon 12 inches of concrete below the stone floor of the 
chamber. The concrete rests on hard clayey soil. The height of the 
top of the slab from the floor is 34 feet, and its height above sea-level 
is 364 feet. 
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