The Plan of the Earth and its Causes. — Gregory. iii 
al effects seem to have been obliterated by the changes of geo- 
logical times. 
References to such changes reminds us that we cannot as- 
sume their occurrence without considering the unending con- 
troversy as to the supposed permanence of oceans and conti- 
nents. 
There are, it must be conceded, many weighty arguments 
in favor of the permanence hypothesis. Many of the last 
great mountain foldings follow the lines of much older move- 
ments ; and if the mountain axes, the "backbones of the conti- 
nents," have occupied the same positions, why not also the con- 
tinents moulded upon them ? Again, some of the great moun- 
tain chains, such as the Andes, run parallel to the nearest 
shore-line, as if the movements that formed them had been 
deflected by the ocean basin. 
The character of the ocean floors, moreover, suggests that 
they have never been continental, as they are at present cov- 
ered by deposits not known in the interior of the continents ; 
and as they are supported by material much heavier than that 
which forms the foundations of the continents. 
These arguments, however, are not conclusive. Great 
earth movements of one date often cut obliquely and trans- 
versely across those of earlier periods. Thus the old north- 
westerly and south-easterly movements of France and Spain 
have been cut across by the east and western movements of 
the Pyrenean-Alpine system. Mountain axes have not al- 
ways been deflected by or limited by existing ocean basins. 
Thus the north Atlantic basin cuts directly across the old 
Hercynian mountain chains, which may at one time have ex- 
tended across the whole Atlantic channel. This is rendered 
probable by three lines of evidence. Thus in north-western 
France, and in the south of the British Isles, there is a series of 
ranges trending north of west, which is cut off abruptly by the 
Atlantic slope. On the opposite shore of the Atlantic in New- 
foundalnd, there is a similar series of truncated ranges formed 
at the same age as those of western Europe, and having the 
same trend. Bertrand maintains (1887) that the resemblance 
between the opposite mountain series is so striking that they 
should be regarded as parts of one mountain system, of which 
the central part has been sunk below the Atlantic. The well- 
