ox SEI3MOL0GICAL INVESTIGATION. 229 



The cliief feature in this list is that with one exception it refers to 

 earthquakes of whicli we know the origin. The exception is No. 42, and 

 it is here included because it refei-s to an earthquake which pro'S^ably dis- 

 turbed the whole of the globe, and had a duration greater than any yet 

 recorded. In Japan I recorded it as having a duration of 5 hrs. 24 mins. 

 In Strassburg it continued 11 or 12 hours. 



In the columns for magnetometer disturbances, especially for Kew and 

 Mauritius, it must not be inferred that the marks necessarily indicate any- 

 thing more than that slight magnetic perturbations have occurred at about 

 the times specified. The Potsdam, Wilhelmshaven, and Pawlowsk records 

 date from 1895. 



Further information has been obtained fro:n the earthquake catalogues 

 published from time to time by Professor Pietro Tacchini in the ' Bollettino 

 della Societa Sismologica Italiana.' 



These records date only from 1895, and refer to Utrecht, Potsdam, 

 Wilhelmshaven, and Pawlowsk. 



What has been gathered from these lists, together with that from 

 replies to circulars, more of which may yet be expected, is tabulated in a 

 uniform manner in the following lists : — 



0, as, for example, ' Potsdam = 0,' means tbat the magnetograpbs at Potsdam were 

 not disturbed. 



D means Declinometer or the unifilar record. 



H means Horizontal Force record. 



V means the Vertical Force, or Lloyd's balance record. 



The times are given in hours and minutes G.M.T. 



Beplies relating to the List on f. 191. 

 {^Earthquakes recorded at Shide, Isle of Wight, 1897-98.) 



1. Records from the Kew Observatory, Richmond, Surrey. 

 Superintendent, Dr. Charles Chree, F.R.S. 



Dr. Charles Chree, F.R.S. , superintendent of the above observatory, 

 tells me that he and Mr. Baker have looked at the curves, chiefly for 

 horizontal force, at the times of the large movements in the Shide list, 

 and he points out that near these times — as near any other set of arbitrary 

 times — there are movements of the ordinary magnetic small wave type. 

 vSuch movements go on for hours, if not for days ; and by some the view 

 is held that they are always, or jiearly always, existent, and might be 

 seen if we had only delicate enough instruments and an open time scale. 

 When earth movements have affected the trace there is a 'burr,' but such 

 a • burr ' might be equally well caused by an assistant entering the room 

 with keys or a knife in his pocket. In only one case — No. 104, June 3 — ■ 

 ■\vas there evidence of a movement not due to natural magnetic causes, 

 excepting one on October 20, No. 141, which might more naturally be 

 assigned to human creation. The June 3 movement would pass for an 

 earthquake, but it took place at an hour when there are frequent move- 

 ments in the building, as absolute meteorological observations are taken 

 then. Traces free from small movements, excepting the vertical force, are 

 rare. On a moderately disturbed day the movements are in dozens, or 

 rather hundreds. In the following list the numbers refer to those on the 

 Shide list, and if these are followed by =• this means that at the corre- 

 sponding dates the magnetometers were not disturbed: 98 = 0. 104. At 



