1921.] Angenheister.—A Study of Pacific Earthquakes. 
215 
for a ray of maximum depth 50 km. The values are v l)C = 4*83 km./sec. ; 
v c0 = 4T2 km./sec., where v oc and v c0 are velocities under the ocean and 
continents respectively. 
Time Curves from 80° to 180 °.—For epicentral distances greater than 
20° P and S travel for so small a fraction of their path through the outer 
crust of the earth that their travelling-time is almost independent of 
whether the waves travel under ocean or continent, so that their time 
curves have universal application. From 20° to 80° these time curves 
are already accurately known, and, as stated in Section III, were used 
for the accurate determination of epicentres from the records of Pacific 
stations. 
Fig. 2.—Time curves according to the three largest earthquakes of the Tonga Deep. 
Ap, Apia; Ad, Adelaide ; We, Wellington; SyO, Sydney (Observatory); SyR, Sydney (Riverview); 
Ho, Honolulu; Ma, Manila ; Tu, Tucson; Vi, Victoria; Ba, Batavia ; Si, Sitka; De, Denver; 
Ka, Kansas; StL, St. Louis; Pa, Panama; To, Toronto; It, Ithaca; Wal, Washington; Wa2, 
Washington; Ot, Ottawa; Ve, Vermont; Ca, Cambridge; Ab, Aberdeen; Bi, Bideton; Br, 
Bromwich; Sh, Shide; Ro, Rome ; Pe, Perth; Ir, Irkutsk ; Ms, Mauritius ; Ta, Tashkent; Pu, 
Pulkowa; Es, Eskdalemuir; Mi, Makeyewka; Db, De Bilt; Ri, Rio Tinto; Al, Alyser; B, 
Barcelona. 
In Gutenberg’s* time curves P and S and their reflections can be 
followed to 106°, and again from 143° to 180°. Between 106° and 143° 
there is a break in the observations. Rudolph and Szirtes published in the 
Phys. Zeitsch. (1st August, 1914) a short note in which they announced 
a new time curve calculated from seventy-four earthquakes, 1906-13. 
According to this note the P waves can be observed continuously to 150°, 
for which epicentral distance the travelling-time is 965 seconds. PP is 
stated to divide at 113° into two parts, which could be followed to 180°. 
Between 143° and 180° one of these branches is probably identical with 
Gutenberg’s so-called P waves. These latter results are so important 
* B. Gutenberg, Nachr. d. Tc. Ges. der Wiss. zu Gott., 1914. 
