186 REPOKT— 1897. 



the evening of that day a submarine earthquake occurred in this locality 

 which was recorded in the Isle of Wight ; and, from the magnitude of the 

 diagrams, it may be assumed that the world was shaken from pole to pole. 

 Following this shaking, great sea-waves spread over the Noi'th Pacific 

 Ocean. The explanation of these phenomena is that the earthquake was 

 produced by fracture of the rocks, not at a point, but over a considerable 

 length, which movement, being accompanied by the displacement of huge 

 masses of material, gave rise to the sea-waves. The sub-oceanic contour of 

 this locality, where the depth of the water increases at the rate of 1,00(} 

 fathoms in 25 miles until the 4,000-fathom line of the Tuscarora Deep is 

 reached, lends itself to this supposition. The only difficulty we experience 

 is to estimate the volume of the matei'ial which must have been more or 

 less suddenly displaced at these great depths to have produced so great a 

 disturbance on the surface of the ocean. It is not likely that it was less 

 than that of the greatest landslide of which we have historical record as 

 having occurred upon the surface of the earth. 



The data we have for calculating the position of the origin of these 

 great disturbances are numerous and exact. Our knowledge of the dissi- 

 pation of earthquake energy, as represented by its destructivity as it 

 radiates, indicates that an earthquake which dislodged sufficient material 

 to disturb the whole of the North Pacific Ocean must, at the very least, 

 have originated 100 miles away from Miyako, on the north-east coast of 

 Nippon, at which places a few houses were shattered. 



The calculations to be found on p. 1.57, strangely enough, bring us 

 exactly to the base of the western boundary of the Tuscarora Deep, above 

 which there are 4,000 fathoms of water. This is a place from which many 

 earthquakes have originated, affording evidences, particularly in this 

 instance, of sudden sub-oceanic changes along the basal frontier of a 

 continent the magnitude of which it is difficult to estimate. 



Submarine Volcanic Action. — If highly heated rocks saturated with 

 water were the only condition necessary for a display of volcanic action, 

 such activities might be as marked in ocean basins as round their margins. 

 The geological distribution of volcanoes, however, shows that before a 

 volcanic magma can expend and find exit on the surface, the pressure due 

 to superincumbent strata must be relieved, which is apparently obtained 

 when they are sufficiently crumpled upwards to form mountain ridges. 

 If, therefore, we seek for volcanic action beneath the sea, we may expect 

 to find the same along submarine ridges, and if we discover the same, as 

 we do along the central ridge of the Atlantic, the conclusion is that along 

 such a ridge an upward brady seism ical movement is in progress, and not 

 far from the region of eruptions there should be a region of earthquakes. 



In certain instances, apparently, as is the case with the Aleutians and 

 the Kurils, so many eruptions have taken place along a submarine ridge 

 that a continuous and almost connected chain of islands has been formed. 

 On the flanks of the most southei'n of the latter group recent marine 

 strata have been raised, which, taken in conjunction with the fact that 

 hardly a year passes without some new eruption being noted, whilst sub- 

 marine shocks of earthquakes are frequent, indicates that Japan may in 

 time become connected with Kamschatka. 



Any attempt to enumerate the various submarine ridges of volcanic 

 activity at present evidenced by these outcrops would be beyond the scope 

 of the present paper. One curious form of evidence, indicating the exist- 

 ence of volcanic activity entirely hidden in ocean depths, is referred to by 



