260 EEroRT— 1898. 



ends of the base, which if joined would form the base of the triangle, are 

 provided with pivots which bear in steel cups. 



The plane of the triangular frame is placed parallel to a wall, and its 

 upper pivot hooks into the upper cup, whilst the lower pivot bears directly 

 into the cup near the floor, which has a lateral and fore-and-aft adjustment. 

 On the apex of the swinging triangle a weight of about 25 kilos, is placed. 

 In one case this was pig-iron and in the other a block of marble. Pro- 

 jecting from each apex is a lilm of glass resting on a drum moving a band 

 of smoked paper at a rate of 60 cm. per hour. At each hour by electrical 

 connections with a chronometer the pointers are lifted for a short interval 

 of time from the recording surface, and time marks are obtained. 



At first these pendulums carried pens writing on paper, and it is 

 instructive to notice the great difTerence in the frictional resistance of 

 these and the ends of rounded glass fibre on smoked paper. 



After a deflection of 3 cm. the ink pen continues to move for 12 

 minutes with a period of 22 seconds, but after a similar deflection with 

 the fibre resting on smoked paper the movement continues for more than 

 one hour, the period being nearly the same. 



This apparatus has yielded several instructive diagrams of earthquakes, 

 the most striking of which is that of the Assam earthquake of June 

 1897. 



Whilst examining the seismoscopes Dr. Cancani sketched one of his 

 own, which he considered extremely sensitive. It consists of six inverted 

 elastic pendulums arranged to stand round the circumference of a small 

 circle. Each of these is a vertically placed steel wire the upper end of 

 which is a spiral terminating with a style. These styles are adjusted in 

 close juxtaposition with the edges of a metal disc with which, if they 

 .should vibrate, they come in contact. Each of these wires is loaded, but 

 at different heights from their base, with a metal ball, and therefore they 

 have different periods of motion. Contact with the disc completes an 

 electric circuit. 



In the Cecchi seismoscope a small column stands freely on a horizontal 

 plate fixed on the top of the style of an inverted pendulum similar to 

 that just described. When this falls, because it is attached by a thi'ead 

 to a catch-controlling clockwork, this catch is released, and the clockwork 

 set in motion. 



Padua. 



Although the time spent at Padua was, I regret to say, extremely 

 short, in consequence of the kindness of Professor Vicentini and his 

 assistant Dr. Pacher, who had arranged seismograms and apparatus for 

 my inspection, much was learned during the visit. The instruments, 

 Avhich are of the heavy pendulum type, are established on the walls of one 

 of the physical laboratories of the University Buildings, which are 

 suiTounded by the traffic of the city. Considering the position in which 

 they are placed on an upper storey, which, as Professor Vicentini remarked, 

 was only occupied from necessity, it is remarkable that so many new 

 and valuable results have been obtained. Although the walls of the 

 University, like most old buildings in Italy, are remarkably solid, they 

 rise from an alluvium foundation, which is very elastic. One result of 

 this is that the movements of the soil due to passing traffic, the ringing 

 of a bell at no gi'eat distance, and the pulsations of Uie ground appa- 



