260 REPORT— 1898. 



If this is the case, then 1 mm. deflection of the writing indices corre- 

 sponds to 0'6 sec. of arc. 



When the pendulum has given to it a swing with a range of motion as 

 shown by the writing indices of 3-5 cm. after nine complete swings, it 

 comes to rest in 1 min. 42 sees. 



The shortness of this interval indicates that in the recording apparatus, 

 especially perhaps with the pens, there is considerable frictional resistance ; 

 a feature in the apparatus which I understood Professor E,icco has the 

 intention of improving. 



High winds and waves beating on the coast result in a tremulous 

 movement of the writing indices, so that if an earthquake occurred at such 

 a time I presume the rapid movements at its commencement might be 

 eclipsed. 



In the centre of a spacious chamber adjoining that in which the large 

 pendulum is installed there is a massive column in the form of a truncated 

 cone, the greatest visible diameter of which is 5 metres. It rises from the 

 floor in the form of a solid circular wall, to the centre of the annular space 

 which this incloses there is an opening. Instruments standing on this 

 can be examined either by walking round the outside or round the inside 

 of this horseshoe-formed pedestal. 



At the time of my visit there were standing upon it eight or ten seis- 

 moscopes, the microseismoscope of Guzzanti and the seismograph of 

 Brassart. 



Amongst the seismoscopes I noted a light spiral spring carrying a 

 weight with a style : if this moved slightly downwards — say less than 

 •5 mm. — it came in contact with a surface of mercury and closed an electric 

 circuit the time of which might be noted in various manners. The 

 essential feature in two other seismoscopes was a small column standing 

 upon an exceedingly small base. In one instance the column stands freely. 

 To place the column in such a position directly by hand would for many 

 people be almost an impossibility. It is therefore suspended by a collar 

 to hang freely in a tube. When the tube is lowered between guides the 

 bottom of the column comes down upon its base and it remains standing 

 upright. 



In another instance the column is Ijrought to a practically upright 

 position by leaning it against a support which by means of a screw is 

 gradually advanced until the column is on the verge of falling. In both 

 cases the columns are in an extremely unstable condition, and, should they 

 fall either by their weight or by making an electric contact, they start a 

 clock or actuate other apparatus which gives the times at which they were 

 disturbed. 



The apparatus employed to yield open diagrams of local shocks is a 

 Brassart seismograph. This consists of a pendulum, 3 metres in length, 

 carrying as a bob a ring of metal weighing 2G-4 kilos. Embracing a style 

 which projects from the bob downwards are two levers arranged as in the 

 large seismograph. These multiply motion relatively to the pendulum ten 

 times, and their outer ends rest side by side on the surface of smoked glass 

 plate which at the time of an earthquake is set free by electric contact from 

 one of the seismoscopes to run at a rate of about 445 mm. per minute. 



The vertical component of motion is obtained either by making a 

 portion of the suspension of the pendulum a spiral spring and treating the 

 heavy bob of the pendulum as a steady point, or from a spring lever 

 seismograph attached to the frame carrying the ordinary pendulum. By 



