The  sampling  of  the  latter  calls  for  little  more  than  a
knowledge  of  mining  as  practised  or  practicable  locall}',
a  good  eye  and  a  sound  grasp  of  the  principles  of
sampling  and  deductions  therefrom,  though  the  last
AAould  seem  to  be  little  enough  understood,  even  by  the
frat€rnit3\

From  this  aspect  of  the  risk-rate  (>•"')?  the  probable
occurrence  of  ore  beyond  the  pick-point,  whether  it  be
the  continuation  of  an  ore-shoot  in  a  t^-pical  vein,  or  the
lateral  extension  of  a  mineralised  part  of  the  porphjT^^^
flow,  though  often  calling  for  the  most  exhaustive  study
of  the  surrounding  district,  is  the  practical  object  of
geological  work.  For  instance,  the  idea  that  a  fair
allowance  for  shoot-extension  would  be  a  wedge  having
a  base  equal  to  the  shoot-length  on  the  lowest  level,  and
terminating   at    a   point   distant   one-half   of   the   shoot-

*  See  ■'Principles  of  Mining."  by  H.  C.  Hoover.  The  above  7  per
cent,  for  risk  may  be  read  as  con-esponding  to  the  writer's  r"'  =  4  per
cent.
32


MODERN   MINE   VALUATION.
length  below,*  is  another  estimate  of  /".  The  practical
application  of  this  allowance  calls  for  the  careful  study
of  the  type  of  deposit,  as  well  as  of  adjoining  mines,,
especially  if  they  be  deeper  or  near  the  same  depth,  and
is  admissible  only  if  they  show  no  cause  to  suspect  a
sudden  diminution  in  the  pay-ore.
Many  will  insist  that  mines  may  not  be  bought  on  a
basis  of  the  ore  proved.     This  is  often  true,  but  in  the


ma^wmmm^^imm

s^'y^vw^s^agRg^

!     Block  3  A.      ^      Blocks.
1  Present   ^slue          \     Present    Value
'       £43.000.              '<        £26.000.
:                 t

Block  1.
Present   Value
£40.000.
Block  2.
Present  Value
£ 65.000.
Block/ZA.
Present  Value
/

£2.000.
~'---.,^                    Bj

ock  4.
