262 REPORT— 1898. 



strengthened with iron straps. A few yards distant from the observatory, 

 and in the same garden, is the residence of Dr. Grablovitz and his office. 



The observatory is practically a lofty, well-lighted room .30 feet or 

 so in diameter. 



In the centre of this there is a massive horseslioe-formed column, on 

 which stand a variety of instruments. On one of the walls is the regu- 

 lator, which is from time to time corrected by noting the time when a spot 

 of light crosses a meridian line drawn upon the floor. This takes place 

 when the sun passes a slit in the wall in line with the mark upon the tloor. 

 Here, as at Catania, there was a three-component Brassart pendulum. 

 Another pendulum had a length of 1 metre, and only records two com- 

 ponents of motion, each of which is multiplied ten times. 



With apparatus of this description, in which the record is received 

 upon a drum revolving on a horizontal axis, Dr. Grablovitz arranges the 

 pen or style so that it hangs vertically, and therefore comes in contact 

 with the side of the recording surface instead of being, as is usually the 

 case, upon the top of the same. Although in the latter case the pens 

 or styles are balanced, I understood from Dr. Grablovitz that his 

 arrangement, especially when the styles are made of a small thin strip of 

 aluminium, is one that minimises f rictional resistance. One apparatus 

 provided with these pens was a pair of horizontal pendulums the lead 

 weights of which were cylinders measuring about 30 cm. by 5 cm. The 

 short arm of these pendulums was 2 cm. and the long arm 40 cm. Quick 

 motion, due to local earthquakes, would therefore be multiplied twenty times. 

 As I saw them they had a period of three or four seconds. If they are to 

 be used to record earthquakes originating at a distance this quantity will 

 be increased ; but even then it is doubtful whether they will do more than 

 record the most pronounced portion of such disturbances. This instru- 

 ment, which is yet in an experimental stage, is the only one I saw whilst 

 in Italy which approximated in its design to modern types of 'steady 

 point' seismographs which have yielded such good results in Japan. 



Side by side with these horizontal pendulums were a pair of large 

 astronomical levels, oriented at right angles, cemented to the pier, and 

 covered with glass cases. They are read twice daily. 



The next instrument was a pair of conical pendulums, the outer 

 extremities of the booms being so arranged that if they moved to the right 

 or to the left they came in contact with a surface of mercury, completed 

 an electric circuit, and set in action an alarm. 



There were also other seismoscopes, but these were not in action. 



My attention was next drawn to a model of an astatic suspension, 

 which Dr. Grablovitz hopes to introduce into seismometry. This con- 

 sisted of a swinging platform carrying an inverted pendulum. By raising 

 or lowering the bob of this pendulum the period of the system is changed, 

 the moment of the platform and that of the loaded mass acting in opposite 

 directions. 



In a room outside the main building of the observatory I saw a vasca 

 sismica and a pair of geodynamic levels. 



The vasca sismica may be described as a shallow circular tank about 

 1-5 metre in diameter and 1 metre in depth. Floating on the surface of 

 the v/ater which this contains there is a disc-formed tray nearly filling the 

 whole tank. From two points 90^ distant from each other, on the edge of 

 this floating tray, connections are made with the short arms, each 8 mm. 

 in length, of two light levers. The long arms of these levers are 80 cm. 



