GRAPHITE  IN  CALIFORNIA. 
355 
objects.  Perfectly  fresh  bark  yields  no  oesculetin  when  thus 
treated. 
The  bark  of  Hymenodictyon  excels um  differs  entirely  in  its 
chemical  characters  and  products  from  cinchona  bark.  Contain- 
ing no  trace  of  quinine,  the  expectations  once  entertained  of  its 
medical  value  appear  to  have  but  little  support  in  fact. — Lond. 
Pharm.  Jour.,  March,  1868. 
GRAPHITE  IN  CALIFORNIA. 
The  principal  plumbago  deposit  of  California,  known  as  the 
Eureka  Black  Lead  Mine,  is  situated  on  the  west  side  of  Ten- 
nessee Gulch,  a  tributary  of  Wood's  Creek,  about  1J  miles 
from  Senora,  the  country  seat  of  Tuolmune  county,  and  about 
68  miles  from  Stockton,  the  head  of  navigation  on  the  San  Joa- 
quin River.  The  mineral  exists  as  a  well  defined  lode,  from  20 
to  30  ft.  wide,  having  a  dioritic  foot-wall  on  the  west,  and  a 
soft  clay-slate  hanging  wall  on  the  east.  The  trend  of  this  lode 
is  nearly  north-east  by  south-west,  and  it  dips  very  irregularly 
to  the  east,  at  some  places  being  nearly  vertical,  and  at  others 
nearly  horizontal.  It  has  been  traced  and  explored  for  3,900 
ft.,  beyond  which  there  are  but  faint  indications  of  its  existence. 
The  whole  deposit,  including  the  walls  and  vein,  is  enclosed  in 
the  limestones  peculiar  to  Tuolmune  and  the  adjoining  counties. 
The  graphite  near  the  surface  is  much  contaminated  with  the 
materials  of  the  clay-state,  which  rapidly  decomposes  on  expo- 
sure to  the  atmosphere.  It  was  this  circumstance  that  delayed 
the  development  of  the  mine,  as  it  wTas  found  impossible  to  sep- 
arate the  earthy  matter  from  the  more  valuable  plumbago. 
About  two  years  since  it  was  discovered  that  the  graphite 
floated  on  water,  when  a  simple  apparatus  was  employed,  which 
separates  nearly  100  tons  per  day,  giving  employment  to  some 
25  laborers  to  wheel  the  stuff  from  the  mine  to  the  arrastre, 
about  50  ft.  distant.  This  separating  process  is  not  now  re- 
quired, for  a  large  portion  of  the  vein  below  the  sur- 
face, at  a  depth  of  40  ft.,  the  graphite  is  cut  out  in  solid  blocks, 
and  sacked  without  any  further  preparation  ;  but  it  is  divided 
by  lenticular  bodies  of  clay-slate,  a  few  inches  thick,  and  some- 
