22 
THE SECRET OF THE BIG TREES. 
evidence upon which it is based is of very diverse types, and varies 
greatly in accuracy and abundance at different periods. For example, 
the low portion of the curve about 1200 B. C. is based on records of 
ancient famines, and upon the fact that at that time great movements 
of desert peoples took place in such a way as to suggest that the des* 
erts had become much less habitable than formerly. A few hundred 
years later the curve is high, because at this time not only did great 
prosperity prevail in regions which are now poverty stricken for lack 
of rainfall, but the kings of Assyria and the other countries lying 
near the Arabian Desert appear to have been able to take their 
armies in comparative comfort across regions where small caravans 
can not now pass, and which even the hardy Arab raiders avoid. 
At a later time, 300 A. D., the curve drops low, because at this period 
a great number of towns were abandoned in central Asia and in all 
the drier parts of the Continent; trade routes which had formerly 
been much frequented were absolutely given up in favor of those 
where water and forage were more easily obtained; and in coun¬ 
tries like Syria stagnation seems to have prevailed, as is indi¬ 
cated by the scarcity of building operations during these years. 
The curve dips low at this point simply because evidences of 'aridity 
began to be conspicuous; but probably it dips too low, for there is 
as yet no means of obtaining exact data. In the seventh century 
A. D. evidence of the same kind as in the third causes the curve to 
drop still lower, but here we have additional proof of aridity in 
the form of traditions of prolonged famines in Arabia. Moreover, 
at about this same time the waters of the Caspian Sea and of other 
lakes without outlets were not replenished by rain, and hence fell 
to a level so low that buildings were built upon what is now the 
bottom of the lake. Then, at a later date, about 1000 A. D., the ruins 
in the desert were partially reoccupied, the old trade routes began 
to revive, the lakes rose higher than their present level, and prosperity 
was the rule in many regions which had formerly suffered from 
aridity. These bits of evidence, gathered here and there, have en¬ 
abled the curves to be drawn, but accuracy is as yet out of the question. 
At most the curves are a mere approximation, showing some of the 
main climatic pulsations, but likely to be greatly modified as further 
investigation is made. On the whole there are indications that 
further knovdedge of the Asiatic curve will prove that it is much 
more like the California curve than now T appears. Yet in the main 
the tw T o curves even now 7 show 7 a considerable degree of agreement, 
and in that agreement lies the strongest evidence that both are cor¬ 
rect in principle, although they may be wrong in detail. 
Let us begin at the left-hand end far back at the time of the Trojan 
War. There, about 1200 B. C., both curves drop very 1ow t , indicat¬ 
ing an epoch of sudden and severe desiccation. That particular 
