When  the  line  MiD  was  extended  backwards  and  the  distance
MiM2  =  10.29  feet  was  laid  off,  it  was  found  to  coincide  with  the
lower  left  hand  comer  of  a  large  rock  lying  flat  against  and  firmly
bedded  in  the  hillside,  6^  feet  to  the  west  of  the  white  oak  tree  shown
in  the  sketch  (Fig.  6  and  Plate  IX,  Fig.  2).  The  rock  measures
1.25  feet  in  direction  up  the  hill  and  3.2  feet  in  direction  along  the
hill.  When  the  line  was  permanently  marked,  the  point  M^  was  re-
ferred to  the  bolt  and  mound  shown  in  the  sketch.  Horizontal  dis-
tance of  M2  from  the  bolt  is  34.14  feet,  and  from  mound  (middle  of
Jiole  in  top  of  marble  post)  40  feet.  Hence  the  "  middle  of  the  Savage
river  where  it  empties  into  the  Potomac  "  is  28.4  and  102^  feet,  meas-
ured horizontally  along  the  boundary  line  from  the  bolt  and  the
mound  respectively.  For  description  of  bolt  and  mound  see  page
133.  The  point  E  has  likewise  been  marked  by  a  cross  cut  in  the
rocky  ledge,  so  that  with  the  aid  of  the  data  given  above  M  can  also
be  recovered  from  E.
