64 REPORTS ON THE STATE OF SCIENCE.—1913. 
District Ill.—W. Pacific, Australia, and New Zealand. 
. : . Instru- No. of 
Station Foundation Seismographs eit Cor. 
Records 
Cairo Eocene Limestone . | Milne, two instruments P. 91 
Tiflis Rock . : . | Milne, Rebeur-Eblert, | P. & 85 
| Bosch, Zollner and 
|  Cancani 
Adelaide Thick Alluvium .| Milne . 4 5 : P. 76 
Batavia Alluvium . . | Milne, Rebeur-Ehlert, | P. & 67 
Wiechert 
Zikawei . Thick Alluvium Omori, Wiechert Ss. 53 
Osaka Thick Alluvium Omori . s. 52 
Honolulu Coral Limestone ./ Milne . 122 52 
Riverview, Sandstone Wiechert Ss. 51 
Sydney 
Manila Alluvium . Gray-Milne, Bertelli, | P. & 48 
Cecchi, Vicentini, 
Omori 
Sydney . Clay and Ironstone | Milne P. 45 
Shale | 
Tsintau | Wiechert 8. 45 
Mauritius . | Alluvium on Basalt | Milne BP: 38 
Kodaikanal . | Rock . . . | Milne Pp: 37 
Calcutta Alluvium . . | Milne lee 31 
Wellington, Milne 1 34 
N.Z. | 
Colombo Laterite | Milne le 27 
Mizusawa Alluvium . ; . | Omori . 5 é 6 8. 24 
Bombay Red Earth above | Milne, Colaba, Omori P. & 22 
Basalt 
Tokio . . | Alluvium . Milne PR; 21 
Perth, West | Limestone | Milne iP: 15 
Australia 
Reykjavick . | Volcanic Materials . | Wiechert 8. 16 
A glance 
has recorded 
has only recorded 15. 
at the preceding tables shows that while one station 
144 of the possible 166 disturbances, another station 
These marked differences in the number of 
records in different places are dependent upon many conditions, and 
at no two stations are the conditions exactly the same. At one, rapid 
changes in temperature may be accompanied by air tremors, which 
may eclipse all but the largest seismic records. In this respect 
I have found marked differences between adjoining rooms. At certain 
observatories insects, particularly small spiders, cause trouble. A 
more important cause leading to differences in the number of earth- 
quakes recorded at stations in the same district is difference in the 
adjustment of the instrument. If two horizontal pendulums have 
different periods, the one with the longer period yields the greater 
number of records. Unfortunately, however, it is the one most 
influenced by air tremors. The expiring efforts of large earthquakes, 
which at a distance from their origin may be represented by minute 
ripples or thickenings in consequence of their smallness, have fre- 
quently been overlooked. Proximity to or remoteness from epicentral 
district has naturally a considerable influence upon the number of 
records obtained at a station. 
