146- REPORT — 1894. 



of which the pendulum can be tilted in the plane perpendicular to that of 

 the silver wire, and the spot of light readjusted to the centre of the scale 

 or photographic paper. Both screws are worked from a distance by long 

 wooden rods. 



A bifilar pendulum, with the changes above described, was erected 

 early this year at the Royal Observatory, Edinburgh. The instrument is 

 also further pi'otected by a cover from heat effects. Dr. Copeland, As- 

 tronomer Royal for Scotland, informs me that, with these arrangements, 

 it is not at all affected by momentary changes of temperature. 



The Greek Earthquake Pulsations of April 1894. 



On April 20 a severe earthquake took place in north- east Greece, 

 causing much damage in several towns and villages. Soon after the news 

 of its occurrence was published I made frequent observations with the 

 bifilar pendulum at Birmingham, and was fortunate enough to watch the 

 o-reater part of the remarkable series of pulsations proceeding from the 

 second great disturbance, that of April 27. An account of these move- 

 ments is given in its proper place below. 



A few weeks later I received from Dr. von Rebeur-Paschwitz a list of 

 the records of the same pulsations made by the horizontal pendulum at 

 Nicolaiew. As these gave a somewhat greater velocity for the pulsations, 

 it seemed possible that conclusions of some interest might result from an 

 endeavour to trace the pulsations as they spread outwards from their 

 origin. I accordingly wrote to the directors of the leading magnetic and 

 geodynamic observatoi'ies on the Continent and in this country, and I am 

 indebted to their courtesy for much information, a summary of which is 

 given below. Additional details I'elating to the Italian observatories have 

 been extracted from the valuable ' Bollettino Meteorico ' (Supplementi 104 

 and 105) of the ' Ufficio Centrale di Meteorologia e Geodinamica ' of Rome. 



The total number of shocks belonging to this earthquake series must 

 amount to several hundred. The strongest were those, already mentioned, 

 on April 20 and 27. Both were felt over the whole of Greece. The 

 epicentral areas seem to have been situated in the eparchy of Locris, and 

 probably not far distant from its capital, Atalante. In the estimates of 

 the velocity which follow I have supposed the earthquake pulsations to 

 start from this town, the position of which is 38° 39' N. lat., 23° 0' E. long., 

 and about 98 kilometres from Athens. For convenience the recorded 

 times have all been reduced to Greenwich mean time. 



Athens (Dr D. Eginitis), 37° 58' 20" K, 23° 43' 48" E. The earth- 

 quakes were registered by Brassart seismoscopes. These are well regulated, 

 so that the times may be regarded as very exact. April 20, 5h. 17m. 5s. p.m., 

 duration 4 seconds ; followed by a second shock at 5h. 17m. 35s. p.m., 

 duration 7 seconds. April 27, 7h. 46m. lis. p.m., a very strong shock, 

 'luration 12 seconds. 



Catania ' (Professor A. Ricco), 37° 28' N.. 15° 4' E. April 20, 

 ah. 23m. 8s. P.M. April 27, 7h. 47m. 19s. p.m. The photographic record 

 of the normal tromometer shows six series of decreasing oscillations, 

 lasting for about 18 minutes. 



Benevento (' Boll. Meteor.'), 41° 8' N., 14° 45' E. April 20, 5h. 19m. p.m., 

 a very distinct trace indicated by the Cecchi seismograph. April 27, 



' The observatory is situated at a short distance from Cutania, but I have been 

 unable to find its exact position. In several cases, the positions of the Italian 

 observatories are only approximate. 



