ON THE FACTS AND THEORY OF EARTHQUAKE PHENOMENA, 69 
Future observation will probably show a connexion between the great sub- 
oceanic seismic tract of the South Atlantic and the South American conti- 
hent on its western sea-board, between Cape Roque and La Plata. It does 
not appear so far to have any connexion with the opposite African coast be- 
tween Cape Palmas and the Bight of Biafra. A better knowledge will also pro- 
bably widely extend the seismic boundary of the Cape of Good Hope along 
both the east and west shores of Africa to the northward, and bring within it 
the great island of Madagascar, as to which nothing is so far known. New 
Zealand (unhappily for its future progress) will afford one of the best regions 
in the world for the study of volcanic and seismic phenomena in their con- 
nexion. 
The earthquake-band of Western Australia, at present so small in propor- 
tion to its vast surface, will probably be found to reach much further towards 
the interior, and embrace Van Diemen’s Land and a considerable stretch of 
the southern coast to the eastward. It remains yet to be observed whether 
even the small surface explored of the east side of the Great Island is sub- 
ject to earthquakes or not. Abyssinia too, though not affording the record 
of a single earthquake, is too closely united with the seismic region of Arabia 
and the mouth of the Red Sea, to be probably perpetually in repose. 
There are great untinted spaces upon our map. The northern and south- 
ern polar regions, immense tracts in North America and in Northern and 
East Central Asia; surfaces in South America nearly as large as all Central 
Europe; the whole African continent except the northern edge and southern 
point; nearly the whole of Australia, and almost the whole of the bed of the 
great ocean, are perfectly unstudied and unknown to us, as respects their 
seismic condition. They appear white, and hence free from earthquake, upon 
the map, but only because there are no observations. 
Future researches will probably, however, show that all these vast tracts of 
land are traversed by earthquake-bands presenting generally the features 
that we recognize elsewhere, and that the ocean-bed, far from the continents, 
although always much less disturbed, for equal extent of surface, than the 
land, and especially than the coast, of the great oceans, is also traversed by 
earthquake-bands continuous with and tracing out their shallowest contours. 
Had navigation been, in times past, as frequent and constant in the Pacific 
and Southern Indian oceans as it has been in the narrower Atlantic, especially 
north of the equator, the former would most probably present, over very much 
of their vast surfaces, light seismic tints such as almost the whole Atlantic 
presents, included as it is within the range of movements transmitted from 
both its western and eastern borders, and also from the foci within its bosom, 
_ connected by seismic lines so closely adjacent, 7. e. with sub-basins so com- 
_ paratively small in area. 
___ Imperfect as are our observations on land, they are much more so upon 
_ the surface of the great ocean that covers three-fourths of our globe; so 
_ that only a very rude approximation, and from very partial data, can be 
‘ made towards the solution of the question, What is the relation of seismical 
_ nergy beneath the land and the ocean ? 
_ _ The result of Perrey’s, memoir ‘On the Basin of the Atlantic,’ (Dijon 
Fi Mém.) assigns, for a period from 1430 to 1847, or 417 years, a total of only 
_ about 140 shocks (or three shocks per annum) observed over an area of 
_ about 24 millions of square miles. If we contrast this with the only tolerably 
_ well-observed portion of the dry land, the great European area, we find 
_ thereon at the least 40 shocks per annum observed upon an area of 1,720,000 
_ square miles, or (allowing for regions included, but never observed), say, 
1,500,000 square miles. There occurs therefore annually in the Atlantic 
