670 PROCEEDINGS OF SECTION E. 
While the slopes or grades of the sea bottom in the basin and 
deep channels is very flat, the few measurements which have been 
made of the sides, one may almost say walls, of the profound 
abyssal deeps, show a very steep angle for subaqueous material 
to form a slope having even a slight degree of stability. The few 
observations made indicate that there exists a slope steeper than 
1 in 20 from the 2-mile level of the surrounding ocean to a depth 
of 54 miles. These wonderful deeps have cenerally a lesser 
extension and are deeper than the height of the highest mountains, 
and it has been conjectured that they have a relation to the 
nearest great mountain range, with which, as it were, they are 
paired, the relation being like that of a model and its mould. 
The causes of the inequalities in the form of the ocean bed are 
no doubt the same as those which have caused the great inequali- 
ties of the land surface, great swelling elevations producing 
plateaux ; slow-moving subsidence, producing troughs like the 
Caspian basin on land, and the larger submarine basins of the 
ocean. 
The abyssal deeps of eke ocean appear to mark areas of rupture 
and extreme faulting of the earth’s crust analogous, but in the 
reverse direction, to the mighty upliftings and crushings which 
have produced our most mighty mountain chains of the class 
which have linear extension. 
We can, therefore, safely conclude that the same onward 
moving waves in the earth’s crust which lift up the continents 
and produce the mountains are at work also under the ocean. 
Some, however, hold that much of the deeper portion of the flat- 
bottomed ocean has never suffered emergence, having always been 
what are termed permanent ocean-beds. The chief argument for 
this assumption is, that material similar in chemical and mineral 
character to that which floors the great depths of the ocean has 
never been detected in any geological formation even of the 
highest antiquity. No student of geology can doubt the enormous 
changes which have taken place in very recent times on land, 
both by placid swelling and sinking, and also by what look at 
first sight as violent disruptions, but which are really movements 
and involvements due to small but frequently repeated movements 
in the upward or downward direction. 
We thus arrive at the following inferences :— 
1. That an extensive terrigenous shelf must indicate a long- 
continued period of stability, with only moderate oscillation of 
the contiguous continental shore line. 
2. That the basins are large, inert areas that have been sunk 
by a slow, unbroken, and wave-like movement, with crests and 
troughs as waves which traverse slowly the crust of the earth. 
3. That the abyssal deeps have been caused by abrupt faulting 
and volcanic fracture. 
