78 REPORT — 1903. 



writes that the two seismographs referred to in the Report for 1902 are 

 now in working order, one at Ponta Delgada, 25° 41' 15" (Ih. 42m. 45s.) 

 W. long., and the other at Horta, 28° 38' 26" (Ih. 54ra. 34s.) W. long. 



From Professor A. F. Griffiths, President of the Oahu College, and 

 Professor W. D. Alexander, also in Hawaii, I learn that the seismograph 

 sent to Honolulu in 1899 is at the U.S. Magnetic Observatoiy near Pearl 

 Harbour. Mr. Weinrich, who has charge of the instrument, has installed 

 it on a concrete pier rising from the bed rock. The instrument room 

 measures 8 feet by 12 feet. It has stone walls 16 inches thick, and is lined 

 and ceiled with boards. The room has ventilators, but the temperature 

 is almost uniform at 75° F. 



Observers using or interested in the establishment of the British 

 Association type of instruments who have during the past year visited 

 Shide were Mr. W. J. Kenny, H.B.M. Consul, formerly of Hawaii; 

 Professor H. F. Reid, of Baltimore ; Mr. C. Michie-Smith, of Kodaikanal ; 

 and Mr. E. Human, of Colombo. The latter gentleman, whose object was 

 to discuss observatory sites and the working of seismographs, came at the 

 suggestion of the Colonial Office. 



As might be anticipated, now that experience has been gained in 

 working the instruments, correspondence with stations has considerably 

 decreased. 



II. The Origin of large Earth^uaJas recorded in 1902 and since 1899. 



On the accompanying map (Plate I.) the origins for 1902 are indicated 

 by small numerals which correspond to earthquake numbers in the Shide 

 registers. These are divided into districts marked alphabetically. The large 

 numerals give the number of large earthquakes which have originated in 

 each district since 1899. Maps corresponding to the one here given can 

 be found in the 'British Association Reports' for 1900, p. 70, and 1902, 

 p. 64. The methods employed in determining origins are referred to in 

 the Report for 1900, pp. 79 and 80. 



The chief feature in the map for 1902 as compared with those for 

 preceding years is the increase of activity shown for the Caucasian- 

 Himalayan district K and the decrease in the Alaskan and Andean regions 

 (A and D). If we omit districts E and A then, as pointed out by Pro- 

 fessor Libbey, a circle of about 70° radius and centre 180° E. or W. long, 

 and 60° N. latitude in Behring Straits passes through the seismic 

 regions of the world which are at the present time most active. On the 

 map this is indicated by a dotted line. The Pacific origins fall on a circle 

 about 75° in radius, with its centre 180° E. or W. long, and 30° S. lat. 



Mr. J. H. Jeans, in his paper on ' The Vibrations and Stability of a 

 Gravitating Planet,' ' suggests that these regions lie on a great circle of 

 which England is the pole, this circle being the equator of the supposed 

 pear-shaped form of the world. The equator for the pear-shaped form, 

 according to Professor W. J. Sollas,^ has its centre about 6° N. lat. and 

 30° E. long. 



'&• 



III. Earthq^iakes and Changes in Latitude. 



In the ' British Association Report' for the year 1900, p. 107, the 

 wanderings of the pole from its mean position are compared for the years 



' PIM. Trans. Royal Soc, vol. cci. p. 183. 



* ' The Figure of the Earth,' Quart. Journ. Geol. Soc, vol. lix. Part 2. 



