352 



THE AMERICAN NATURALIST [Vol. XLI 



at* any given point is, therefore, the vertical between these two 

 lines, read from the scale at the extreme right of the chart. 



The continuous horizontal immediately below the last species 

 enumerated, represents the altitude of the mouth above sea-level. 

 The profile line indicates the drop in the stream. The approxi- 

 mate altitude of any given point along the stream is shown by the 

 vertical between the two above mentioned lines, and read from 

 the scale at the right. 



The continuous horizontal in "Valley Cross Sections" repre- 

 sents the stream, on either side of which is shown a section of the 

 countr}' for one and a quarter miles. In these cross sections at 

 every mile point the geologic formation can be indicated. 



The current, width and bottom data are self explanatory. In 

 the "Miscellaneous Data," bridges, marshy regions, dams, etc., 

 are represented so far as possible, by the conventional signs 

 employed by the U. S. Geological Survey, thus: 



Bridges (A) e.g., below the one mile mark, at the 



two mile mark, etc. 



Woodlands (B) " at the one mile mark. 



Swamp (C) " between the one and two mile 



Important Tributary (D) represented by a forked wavy line. 



The position of the tributary line 

 in the upper or lower part of the 

 "]Misc. Data" space indicates 

 that the tributary enters the stream 

 from the right or left side respec- 

 tively. 



" at the 1.25 mile mark, (Enters 



from the left side.) 

 " at the 2.6 mile mark. (Enters 



at the 5.8 mile mark, 

 from the right side.) 



