30 
FIFTEENTH REPORT. 
i lie British Isles and Africa-Arabia, even including those which run in 
the line of creep and which were formed by pressures at right angles 
lo it. The great Scandinavian overthrust is not available for western 
Europe and the Alps are the main reliance. To get upwards of 1000 
miles of crustal shortening in between Scotland and Africa-Arabia. or 
more properly between the English Channel and those southern limits, 
since England has no Tertiary mountains, certainly seems more than 
can be reasonably granted. 
Take South America and Africa. The evidence is that their coasts 
match together and the inference is that they have moved apart at 
least -500 miles between Guinea and Brazil and upwards of 1000 miles 
more than that further south. Mr. Taylor thinks they only parted from 
the mid- Atlantic ridge, which would give each an excursion of about 
1000 miles. Now the case of South America is radically different from 
that of North America in that the Pacific ridges are not even a little 
available in explanation of the creep, and he is, I believe, compelled to 
rely to an undue extent upon the deformation of the western border of 
the continent. The width of the sheet diminishes toward the south so 
that the conditions become increasingly difficult. Whereas just below 
the equator, there is something like 2500 miles in which to place 1000 
miles of shortening, further south there is only half that width. Unless 
the eastern Pacific bottom, and the ocean is very deep for a long dis- 
tance off the coast of South America, can come to the rescue with an 
improbable amount of crustal overthrust, we must be prepared to con- 
cede to South America as much puckering as that assigned to the 
Pacific border of North America, 75 miles, the Appalachian 88, the Alps 
74. all added together and the total multiplied by 4! 
For Africa, it seems necessary to grant also 1000 miles of crustal 
creep (toward the east) and the whole can be accounted for only by 
very great foldings and thrusts which have not yet been found in the 
African land. It is true that exploration is not yet complete enough 
to settle such a point, but the great resistance offered by the Indo- African 
mass against the southward pressure of Eurasia, which resistance would 
be necessary to produce the observed Tertiary foldings along the south- 
ern border of the creeping sheet, this great resistance of itself presup- 
poses that same great stability and rigidity that is indicated by what 
is known of Indo-African geology. Such a rigidity is to be reconciled 
with an undue amount of hypothetical thrusting and shortening, if it 
is to be granted that Africa, crept slowly away from the mid-Atlantic 
ridge in Tertiary time. In fact, Mr. Taylor does not claim that. He 
hopes to avoid the difficulty by placing the (eastward) drifting of 
Africa, before the Mesozoic. How to show the untenability of that posi- 
tion in few words would be very difficult, but it becomes perfectly clear 
when these crustal movements are regarded broadly in the light of 
all Ihe facts that I have heretofore presented, that Africa’s principal 
excursion had to be simultaneous with those of all the other continents. 
T must refer to all the evidence T have compiled and reaffirm that the 
crustal sheet which is now Africa, was up to the end of Mesozoic time 
structurally continuous with both the Americas whose coast lines match 
with it like fragments of broken slate. The general stratigraphical ar- 
rangement of its borders corresponds, the surface geology corresponds. 
