392 J. C. Ih'aiuicr — TJie Scrro <lc Jaeohina. 



III. Tlie third theory is that of a single fault along the 

 eastern face of the range, with the downthrow on the west 

 and the subsequent denudation of the uplifted eastern side. 

 According to this theory, the structure would be something 

 like that shown in the acconii)anying figure. 



There seems to be no special objections to this theory unless 

 it be the great depth required for the theoretical single fault. 



The remarkable fact that tiie great Serra de .facobina is cut 

 entirely in two at several places by streams flowing through 

 steep-sided gorges will be discussed in a later chapter on the 

 geography of the State of Bahia. 



The following questions should be kept in mind by those 

 who may hereafter have opportunities to study the geology of 

 the Jacobina range : 



1. Are there always four parallel ranges, or is this appear- 

 ance misleading? 



il. Is the Jacobina range of the same geologic age, and has 

 it the same general history as the smaller quartzite ridges on 

 the plains botli east and west of the range, and mentioned in 

 this Journal, Oct., 1910, p. 263. 



