Method  of  tanning  Leather . 123 
by  obferving  a certain  folid  fcum,  like  the  flakes  of  very 
thin  ice,  which  collects  and  forms  itfelf  on  the  furface  of 
the  lime-water. — As  long  as  you  find  this  Iblid  fcum 
floating  on  the  top  of  the  water  in  the  ciftern,  fo  long 
you  may  conclude  that  there  is  no  neceffity  for  throwing 
in  frefh  lime. 
xii.  But  when  the  fcum  ceafes  to  appear,  or  you  find 
from  the  tafte  that  the  lime-water  is  not  fo  ftrong  as  it 
ought  to  be,  you  muft  then  take  out  the  plug  from  the 
bottom  of  the  ciftern,  and  clear  it  by  fweeping  away 
the  grofs  remains  of  lime:  and  after  you  have  cleaned 
the  ciftern,  begin  your  brewings  of  lime-water  a- new, 
and  proceed  in  the  manner  already  directed,  as  to  ftirring 
up  the  lime,  and  leaving  it  to  fettle  for  the  neceffary 
time,  fo  as  to  have  your  lime-water  perfectly  limpid.  In 
this  manner  you  may  go  on  from  year  to  year,  and  con- 
ftantly  keep  yourfelf  in  ftock  with  refpetft  to  lime-water. 
xiii.  It  is  this  lime-water  which  is  now  to  be  ufed  in 
making  your  ooze  inftead  of  the  plain  common  water ; 
and  this  is  all  the  difference  between  the  old  and  the 
new  method  of  tanning;  for  when  your  ooze  is  pre- 
pared, by  fteeping  your  bark  in  lime-water  (in  the 
letches,  as  you  do  at  prefent,  only  running  it  through 
two  letches)  you  are  to  make  ufe  of  it  in  the  very  fame 
R a way 
