ALCOHOLOMETRIC  SCALES  OF  RICHTER  AND  TRALLES.  319 
on  Chemistry ;  and  finally  there  is  seen  in  "  Meissner's  Areome- 
try"  (Vienna),  an  engraving  of  the  two  scales,  marked  "  Tralles  " 
and  "  Richter,"  placed  side  by  side  in  conjuction  with  a  scale  of 
specific  gravity.  All  these  authorities  agree  closely  with  the 
table  of  comparison  by  Booth,  and  prove  conclusively  that  the 
scale  of  the  Berlin  instrument  marked  Richter,  does  not  indicate 
percentage  by  weight  correctly,  as  has  been  asserted  and  general- 
ly believed. 
I  trust  that  my  motive  for  making  the  above  remarks  may  not 
be  construed  into  a  desire  to  detract  from  the  merits  of  the  foreign 
instruments  used  here ;  but  as  a  manufacturer  of  similar  instru- 
ments, I  do  not  desire,  where  such  wide  discrepancies  occur  in 
comparing  my  hydrometers  with  others,  to  have  the  difference 
pointed  out  as  a  proof  of  error  on  my  part. 
Under  the  title  of  foreign  instruments,  I  include  most  of  those 
sold  in  this  country  as  imported,  but  actually  made  here  and 
copied  after  the  genuine  Berlin  ones  more  or  less  carefully,  ac- 
cording to  the  price. 
It  may  be  said,  perhaps,  that  as  the  scale  of  percentage  by 
weight  is  but  seldom  used,  the  error  is  not  a  very  important  one; 
still  as  it  may  be  referred  to,  all  source  of  error  should  be  avoid- 
ed, particularly  in  an  instrument  of  such  general  employment. 
What  I  have  said  may  be  the  means  of  explaining  away  un- 
pleasant differences,  which  are  often  occasioned  by  the  use  of 
erroneous  instruments.    Yours,  respectfully, 
W.  H.  Pile. 
Philadelphia,  June  \2>th,  1856. 
[Note  by  the  Editor. — Dr.  Pile  informs  me  that  the  scales  of  his  alco- 
holometers are  computed  directly  from  the  published  tables  to  which  he  re- 
fers. He  also  graduates  hydrometers,  showing  specific  gravity,  intended 
more  particularly  for  Pharmaceutists  and  Chemists ;  these  latter  instru- 
ments are  by  far  the  most  important,  and  second  only  to  the  specific  gravity 
bottle  in  the  scope  of  their  application,  and  in  my  experience  with  them, 
are  sufficiently  accurate  for  all  practical  purposes. 
We  have  examined  several  of  the  Berlin  alcoholometers,  and  find  the  num- 
bers as  given  in  the  above  article  to  be  correct  The  tables  are  also  quoted 
correctly.] 
