DRAINAGE PROBLEMS 387 



It is perhaps somewhat inappropriate for one who has only made a 

 flying trip across a large region not to accept the conclusions of another 

 who has gained a close acquaintance with it by long residence and numer- 

 ous journeys ; nevertheless I am constrained to differ in many ways from 

 the theoretical statements made in the above citation. In the first place, 

 the directness of the "main watershed," which is shown as a straight line 

 on the map in Professor Schwarz's paper, appears to me simply as one 

 of those many examples of accidental coincidence of which the world is 

 full, and hence of the same order as that class of coincidences noted when 

 the rectilinear prolongation of a fault line, determined by geological evi- 

 dence in one district, leads to a river course, mapped in an adjacent dis- 

 trict without any evidence of its being related to faulting. Such a coin- 

 cidence may be determined by a causal relation, and it may not. The 

 directness of the main South African watershed on which Schwarz lays 

 much emphasis is, however, more imaginary than real, for it is drawn 

 as a direct line only by making the unwarranted assumption that the 

 present head of the Orange river in the Stormbergen and Dra kensbergen 

 of Basutoland, which is about 150 miles southeast of the direct line, is a 

 later extension of the original head beyond the assumed main or direct 

 watershed. It might be suggested with greater probability of correctness, 

 it seems to me, that the original head of Orange river lay even farther 

 southeast of the so-called "main watershed" than the present head does, 

 and thus departed even more from the direct line then than it does now ; 

 the evidence for this view being found in the peculiar truncation of the. 

 geological structures along the Cape Colony-Natal coastline, already 

 alluded to, and illustrated in figure 1. Furthermore, the main water- 

 shed as drawn by Schwarz follows divides that must be of very different 

 origins and of very different dates of development; it is therefore a line 

 that brings together incongruous elements and treats them as if they 

 were congruous. This may be seen by a review of its several parts. At 

 its beginning near Cape Town it runs between the opposing and com- 

 peting headwaters of rivers that drain longitudinal valleys between the 

 folded mountains, and whose present separation can not reasonably be 

 taken as still closely accordant with the initial divide when the subcon- 

 tinent first rose from the sea. The present divide is the result of long 

 competition by rival streams, as later pages (274 et seq.) of Schwarz^s 

 paper clearly show. At the other end of the line, near Delagoa bay, the 

 divide is drawn obliquely between two east-flowing streams by which the 

 escarpment of the interior plateau is drained to the Indian ocean; and 

 these streams must be of much later origin than the first elevation of the 

 continent, for they are evidently related to that modern displacement 



