Mr. Matter on the Dynamics of Earthquakes. 103 
tant coast, gives no indication of whence it came, or in what direction it set out; that the 
great sea wave may intersect the direction of the previous earth wave or shock at any 
angle, or even travel in the opposite direction, as, for instance, amongst the islands of the 
tertiary formation, on the coast to the east of the map; and that the interval of succes- 
sion between the shock and the great sea wave will vary in different localities. Thus, 
to the north-east of the map the shock and sea wave follow each other closely in the deep 
water, while at the south-west, in the shallow sea, the earth wave of interval VII. corres- 
ponds to the great sea wave of interval 13 ; and again, to the north-west, in the deep bay, 
the earth wave IX. corresponds to the sea wave 19. 
The diagrams (1, 2, 3) Fig. 9, Plate II., show the variable forms which the closed 
curves of the earth wave cotidal lines may assume, in the same uniform formation, accord- 
ing to the nature and position of the original disturbance. Where, as in (1) this is at a 
single point, the curves will be nearly circular; where the disturbance is along an uniform 
right line, they will be ovals (2); and where the original impulse comes simultaneously 
from several distinct points, the curves will be irregular closed figures of contrary flex- 
ure (3). All these are subject to the changes already described in passing from one for- 
mation to another, 
Prater DT, 
Fig. 1. Diagram illustrative of the internal motions of a fluid wave. (Weber’s Wel- 
lenlehre). The strongly marked curveis the outline of the wave in its transit towards the 
position shown by the similar dotted line. During the period of one phase every fluid 
particle in the wave has described one complete revolution, as indicated by the arrows 
and circles. The latter becomes elliptical in descending in a fluid of given depth. 
Fig. 6. A section illustrating the origination and progress of the great sea wave by 
three diagrams, referring to successive short intervals from the moment of impulse by the 
submarine elevation or eruption. A, shows the single hillock or mass of water first 
elevated. In B, this has formed one great circular or oval wave, and within it a smaller 
one (of oscillation). In C, the further progress to land of the great sea wave is shown, 
and the formation of another wave of oscillation. 
Fig. 3. A section showing the effects upon the great sea wave, of its coming from 
deep water upon a shore, which suddenly shelves by steep escarpments. In D, the great 
sea wave advances as a solitary mass with equal slopes front and rear over the deep sea. 
In E, this has just reached the edge of soundings. The front face of the wave has become 
steep, the rearward slope flattened, and the water at the beach is in the act of receding. 
In F, the solitary wave has broken into several smaller ones, having altitudes bearing rela- 
tion to the shallow water beneath, and the foremost is about to form a great ‘‘ breaker” 
upon the shore, having no longer depth to remain unbroken. 
