Page:The origin of continents and oceans - Wegener, tr. Skerl - 1924.djvu/58

34 of propagation of the surface seismic waves through continents with those through oceanic areas, and found the following values:—

Even if individual results do sometimes overlap, a considerable difference can on the average be recognized to the effect that the velocity of propagation through the oceans is about 0.1 km. per second greater than through the continents. This agrees with the expected theoretical values obtained from the physical properties of volcanic igneous rocks.

On the other hand, Tams also tried to combine the observations of as many earthquakes as possible, and thus obtained from the velocity values of 38 Pacific earthquakes an average value of 3.897 ± 0.028 km./sec., and from 45 Eurasian or American earthquakes 3.801 ± 0.029 km./sec., that is, practically the same values as above.

Angenheister also has recently examined the seismical difference between ocean basins and continental