60 REPORT— 1902. 



Strasburg, Toronto, Victoria (B.C.), San Fernando (Spain), Cairo, Cape of 

 Good Hope, Calcutta, Bombay, Ivodaikanal, Batavia, Trinidad, Balti- 

 more, Mauritius, Perth, and Irkutsk. To these is added a list of local 

 earthquakes observed in 1901 in Japan. A register of earthquakes 

 observed by Mr. G. Hogben at Wellington, in New Zealand, commencing 

 October 3, 1900, will appear in the next Circular. It is expected that 

 these will be supplemented by a corresponding register drawn up by 

 Mr. Coleridge Farr, of Christchurch, in New Zealand. Mr. Hogben is- 

 inclined to the opinion that many of his records refer to disturbances 

 originating in the Antarctic regions, and these he has arranged to 

 exchange by means of the relief expedition with those which may have 

 been obtained by the landing party from the ss. ' Discovery.' 



The last instruments despatched were those sent to Mr. F. A. Chaves, 

 Director of the meteorological station at St. Michael, in the Azores. 

 They left the maker, R. D. Munro, Granville Place, King's Cross Road, 

 London, on May 16 of this year. 



II. 2'he Instruments regularly in use at Shide. 



1. A photographing recording horizontal pendulum oriented north 

 and south. This is the type of instrument similar to those in use at tlie 

 other stations. It is adjusted to have a period of seventeen seconds, and 

 with this adjustment a 4° turn of the calibrating screw results in a 

 deflection of the outer end of the boom of 14 mm. As in all instruments 

 a 1° turn of the sci'ew causes a tilt of 1"'9, the above adjustment means 

 that a deflection of 1 mm. at the outer end of the boom is equivalent to 

 a tilt of 0"'54. This stands on a brick pier 18 inches square and 

 4 feet high above its footings, which rest on a beds of concrete above 

 the chalk formation. 



When a rope is placed round this column 2 inches below its upper 

 edge, and this is pulled, the deflection of the upper surface of the column 

 is equivalent to 0""095 per 1-lb. pull. 



For certain experimental purposes this adjustment of 14 mm. deflec- 

 tion for 4° turn of the calibi'ating screw is the one now adopted at Kew, 

 Bidston, and Edinburgh (see p. 75). If the instrument is regarded as 

 a 'steady point' seismograph, and records horizontal motion, such motion 

 is theoretically multiplied 6 '7 times. 



2. A pair of pendulums similar to the above oriented north-south and 

 east-west. This instrument is referred to under the name of its donor, 

 Mr. A. F. Yarrow. The booms of this instrument swing on the same 

 vertical upright. The one recording north-south motion has the same 

 dimensions as those of the type instruments. The other boom, recording 

 east-west motion, is only 5^ inches in length ; but there is cranked to 

 it at right angles a light recording pointer, the arrangement being 

 similar to that shown in fig. 1. By thi?. device the records of two com- 

 ponents of motion are obtained side by side upon the same band of 

 paper. 



This instrument is installed in a building about -^0 yards distant 

 from that in which the type instrument is placed. It stands upon a 

 rectangular brick column, the east-west dimension of which is 18 inches, 

 and the north-south dimension is 37 inches. This is 5 feet 3 inches 

 in height above its footings. Its deflection constant, determined as 

 above, is in an east-west direction, 1-lb. pull = 0"'14. In a north-south 



