APPARATUS  FOR  TAKING  SPECIFIC  GRAVITY,  175 
there.  By  the  aids  of  a  very  large  steelyard  beam  and  copper 
kettle,  we  were  enabled  to  take  the  specific  gravity,  but  could 
not  make  it  higher  than  that  of  compact  quartz.  The  result 
seemed  so  questionable,  that  we  obtained  permission  to  break  up 
the  rock,  and  found  that  what  little  gold  it  contained  was  at  the 
surface. 
Not  only  were  ores  brought  to  us  from  California,  to  be  esti- 
mated, but  also  from  other  mining  regions,  and  of  various  metals  ; 
but  chiefly  gold  and  silver.  As  the  specimens  were  of  all  sizes, 
these  demands  upon  us  often  proved  embarrassing,  since  it  was 
necessary  to  have  beams  suited  to  them,  and  with  attachments 
for  weighing  in  water.  We  therefore  had  frequent  recourse  to 
the  method  advised  by  the  elder  Dr.  Patterson  (formerly  Presi- 
dent of  this  Society,)  which  consisted  in  using  a  jar  or  pitcher, 
rather  larger  than  the  specimen,  and  not  over-large  at  the  mouth  ; 
this  was  filled  with  water  up  to  a  marked  line  ;  and  then,  by  in- 
troducing the  specimen,  and  bringing  back  the  water  to  the  same 
line,  so  much  water  was  removed  as  was  just  equal  in  bulk  to  the 
bulk  of  the  specimen ;  the  weight  of  this  water  gave  the  divisor, 
the  weight  of  the  specimen  (taken  while  dry,)  the  dividend,  and 
the  quotient  was  the  specific  gravity. 
The  results  thus  obtained  were,  generally,  as  satisfactory  as 
those  by  the  usual  method.  And  here  it  may  be  interesting  to 
cite  a  few  examples  from  our  minutes,  of  specimens  estimated  by 
one  or  other  of  the  processes  mentioned,  and  afterwards  melted 
down  and  assayed  as  regular  deposits. 
1.  A  lump  of  quartz,  containing  gold,  found  by  two  Mexicans 
of  the  "  Sonorian  camp,"  in  California,  weighed  265  J  ounces: 
assuming  the  quartz  at  the  sp.  gr.  of  2-60,  the  amount  of  gold 
appeared  by  sp.  gr.  of  the  lump,  to  be  209  J  ounces ;  the  actual 
amount  was  211J-  ounces. — 2.  Another  lump,  where  we  assumed 
the  matrix  at  2-64,  gave  an  estimate  of  100J  ounces  of  gold  ;  the 
actual  product  was  100  l-10th  ounces — 3.  Four  pebbles  taken 
together,  estimated  at  77  ounces ;  actual  content  76  8-10th 
ounces.  And,  lastly,  a  lump  which  had  been  bought  in  California 
for  800  dollars,  and  which  weighed  408-J  ounces,  gave  an  esti- 
mate of  89 J  ounces,  or  1572  dollars,  taking  the  matrix  at  2-63; 
the  actual  yield  was  91  2-10th  ounces,  or  1602  dollars  ;  the  fine- 
ness being  850  thousandths.    In  this  case  there  was  an  error  of 
