240 



HILLS AND DALES. 



If we put L equal to the whole number of lines, and P equal to the 

 whole number of points, we find that F, the number of natural districts 

 named from a hill and a dale together, is equal to W, the number of water- 

 sheds or watercourses, or to the whole number of summits, bottoms, passes, 

 and bars diminished by 2. 



Chart of an Inland Basin. 



/,, /,, /,, /,. Lowest points, Bottoms or Immits. 

 S t . Highest points, Tops or Summits. 

 Bars between regions of depression. 



S lt *!?,, 



lt t , B f 



P lt Pj Pp Pf P f Passes between regions of elevation. 

 /, B t I t &c. Lines of Watercourse. 



S l P, S t <fec. Lines of Watershed. 

 Dotted line. Contour-lines. 



