448 J. F. NEWSOM 
Shore deposits usually have a slight seaward dip. It hap- 
pens, therefore, that the streams entering lagoons behind barriers 
may not only have their courses determined early in their history, 
and that subsequent erosion after the land becomes elevated 
tends to deepen the channel in the position determined, but 
also that this position is parallel with the strike of the strata. 
The subsequent tendency of the stream, therefore, is to remain 
in this original course established for it by the lagoon, as shown 
in Figs. 2 and 3. 
If the coast, along which such stream deflection occurs, 
happens to be rising, or if the barriers are being added to from 
the seaward side, the barriers, at first narrow and low, may 
become gradually wider and higher and finally form a considera- 
ble land area. In this new area a new drainage system will 
develop, a portion of it being drained landward to its old lagoon, 
the rest draining either directly or through a new lagoon, into 
the ocean, as shown in Figs. 3 and 4. 
If the land level remains unchanged, the lagoon is left inland 
and controls the drainage of the region on its landward side 
with little or no tendency toward erosion. If, however, the land 
becomes slowly elevated, the old ‘lagoon portion” becomes an 
active stream and cuts out a channel in and along the strike of 
the new rocks. As the shore becomes more and more elevated, 
and the stream is left further inland, this portion of the channel 
becomes more firmly established in its course. Thus it becomes 
an inland stream, which had a greater or less portion of its 
length originally established parallel with the coast, with the 
contact between groups of strata and also with the strike of the 
rocks, and not across the strike or outcrop, as is so commonly 
taken for granted for the original courses of streams. (Fig. 3.) 
It is obvious from what has been said that the “lagoon por- 
tions’’ of streams will be determined in a direction approximately 
parallel with the general direction of the contacts of the newly- 
formed geologic groups; they may be directly along this line, 
or they may be several miles on either side of it. 
Fig. I may be taken as a type to illustrate this. Here the 
