THE QUATERNARY ERA IN SISTAN. 289 
(c) Rhythmic Warping Theory. — The third possible explanation of the strati- 
graphic series at Sistan is awarping of the crust, whereby the lake was again and again 
poured from one side of the basin to the other or, what amounts to the same thing, 
the streams were deflected and a lake accumulated first on one side and then on the 
other. This theory possesses one inherent though not insunnountable difficulty. It 
demands a fonn of warping of which we have no proved examples elsewhere, and 
which is radically different from that which has taken place in neighboring basins 
and in the world at large. The progress of geolog}- has led to two conclusions which 
are not in harmony with the theory of warping as applied to Sistan. In the first place, 
earth-movements are characterized b}- irregularity rather than regularit}-. They 
occur spasmodically, now a great movement, now a minor one ; now a short interv^al 
of rest, now a long interval. The phenomena of Sistan demand an opposite char- 
acter, approximately equal movements occurring at approximately equal intervals. 
In the second place, earth-movements are cumulative ; that is, the main changes of 
a given period consist of repeated impulses in the same direction. For instance, if 
the world as a whole be taken as an example, the old idea that the oceans have 
become continents and the continents oceans is abandoned. Almost eversone now 
believes that the continents and oceans were differentiated far back in early eras, 
and that in spite of temporary' depressions the continents have steadily increased in 
height and area and the seas have grown deeper. The same holds true in smaller areas. 
For example, in the faulted basin region of the western United vStates, it has been 
shown by Gilbert, Russell, Davis, and others that there has been continued move- 
ment along the same fault lines, and during a given epoch that movement has been 
unifonnly in one direction. If there have been reversals, they have only occurred 
after a long lapse of time, during which the internal forces suffered an entire read- 
justment. Or lastly, to take an example close to Sistan, the basins of Eastern Persia, 
as has been shown above, ha\-e gradually grown smaller through Tertiarj- and 
perha])s Quateniarj' times, by the progressive warping and elevation of the strata 
along their edges. In not a single instance has evidence been found to show that 
a basin has alternately grown smaller and then larger. To put it briefly, the move- 
ments have been cumulati\e, not undulatory. If the red and green clays of Sistan, 
however, are to be explained by movements of the crust, those movements nuist 
have been preeminently undulatory — rhythmic pulsations as regular almost as the 
beating of the heart ; and the final result of a long series must have been to leave 
the countr}- in the same condition as at the beginning. These objections do not 
prove that the theory of warping is untenable. They merely show that a warping 
of a peculiar sort is demanded different from anything of which we have knowledge 
elsewhere. 
Granting, then, the possibility of rhythmic cmstal movements by which the 
lake and rivers of Sistan may have been deflected first to this side of their basin and 
then to that, do the red and green clays show all the expectable features ? In all 
but one respect they do. The amount of warping demanded by the tlieory is so 
slight and may have taken ])lace .so slowly that the streams encroaching upon the 
abandoned lake bed would spread into broad sheets and would lay down subaerial 
