264 REroRT— 1808. 



Although continuous records of earth movements are made at Rome, 

 the chief work beyond the compilation of the otiicial records is that of 

 testing and experimenting with new forms of apparatus. 



The continuous recorders are three pendulums. The larger of these, 

 which is IG metres in length, and carries amass of 200 kilos, relatively, 

 to which motion is magnihed twelve times, had, I understood, gone to the 

 exhibition in Turin. One which I saw, and known as the Seismometo- 

 grafo Medio, is 8 metres in length, and carries a mass of 100 kilos., 

 with pointers magnifying ten times. These pointers are pens carrying 

 an ink containing much glycerine. 



In general form they are like the pens used on the Richard meteoro- 

 logical instruments, but tJiere is some difference in their construction. 



Ihey rest upon a band of paper usually moving at a rate of 30 cm. per 

 hour, but at the time of an earthquake, for a period of 1^ minute, this- 

 speed is increased to 120 cm. per hour, and until the earthquake ceases 

 this speed is continued. 



When the pendulum is caused to swing, so that the writing indices- 

 have a range of 2-5 cm., it comes to rest after ten complete oscillations 

 within a period of 11 minutes. The period therefore is a little over 

 one minute ; that is to say, a pendulum with a free period of hardly six 

 .seconds is increased to more than sixty seconds in consequence of the 

 damping action of writing indices (?). 



This apparatus, together with other instruments, is in the basement of 

 the building, and I understood, like that at Catania, indicates tremors due- 

 to wind and occasionally the effects of traftic. 



Near to it is a Brassart three-component seismograph, 1'5 metre 

 long, carrying 10 kilos., and multiplying motion ten times. 



There were also three seismoscopes : one consisted of a light spiral spring, 

 carrying a weigiit from which depended a second spiral with a weight, the- 

 style of the. latter being at rest just above a surface of mercury. 



A second seisnioscope was a pendulum the style of which hung freely 

 in a small hole in a brass plate. By a slight movement the style comes in 

 contact with the plate, when an electric circuit is completed. 



The third seismoscope, designed by Dr. Agamennone, was the most 

 sensitive. It consists of two inverted pendulums having different periods.. 

 The upper end of the quicker of the two passes through but without 

 touching the sides of a small hole in a metal plate carried on the slower 

 vibrator. A movement of either results in contact, when an electric 

 circuit actuating a magnet releases the record-receiving surface of a 

 Brassart seismograph, or by some other means records the fact that there 

 has been movement. 



liocca di Tapa. 



I left Rome to visit Rocca di Papa in company with Dr. A. Cancani, 

 the director of the observatory at that place, and the veteran seismologist/ 

 Professor M. S. di Rossi. As far as Frascati Me travelled by raU, 

 after which came a drive of H hour, when we found ourselves oppo- 

 site the Albergo Angelletto in Rocca di Papa, some fifteen or twenty 

 miles S.E. from Rome, looking down upon the Campagna. From this 

 point there is yet a steep climb, up streets and lanes through the garden of 

 Professor Rossi, past the caves in which he made his historical tromo- 

 metrical researches, and then by a zigzag pathway through a wood before 

 the observatory is reached. 



