Method  of  tanning  Leather.  1 1 3 
fufficiently  clear  for  enabling  any  intelligent  tanner  to 
avail  himfelf  of  my  improvements. 
I beg  you  will  prefent  this  paper  to  the  Society;  but, 
as  it  cannot  be  underftood  by  gentlemen  who  are  not 
already,  in  fome  degree,  acquainted  with  the  ordinary 
procefs  of  tanning,  I muft  requeft  their  indulgence  while 
I mention  the  principal  operations  in  this  branch  of 
manufacture. 
The  ufe  of  tanning  is  two-fold;  firft,  to  preferve  the 
leather  from  rotting;  and,  fecondly,  to  render  it  imper- 
vious to  water. 
An  infufion  of  any  ftrongly-aftringent  vegetable  will 
ferve  to  tan  leather,  fo  far  as  to  prevent  its  rotting;  but 
if  this  vegetable  does  not  contain  a good  deal  of  gum- 
refm,  it  will  not  anfwer  for  enabling  it  to  keep  out  water : 
and  hence  it  is  that  oak-bark,  which  is  more  abundant 
in  the  gummy-relinous  part  than  any  of  our  common 
indigenous  aftringents,  is  preferred  to  all  other  fubftances 
for  the  purpofe  of  tanning. 
The  tanners  prepare  their  bark  by  gently  drying  it  on 
a kiln,  and  grinding  it  into  a very  coarfe  powder.  They 
then  either  ufe  it  in  the  way  of  infufion,  which  is  called 
ooze;  or  they  ftrew  the  dry  powder  between  the  layers 
Vol.  L XVIII.  Q of 
