126  Dose  Measures  and  Measured  Doses.  {AmMa?ch,f902.rm' 
tea,  dessert,  and  tablespoon  mark,  and  also,  as  nearly  as  this  is  pos- 
sible, gives  the  distance  in  millimetres,  from  the  bottom  of  the  glass 
to  the  tablespoon  mark,  and  then  the  distance  between  the  tea  and 
tablespoon  mark. 
A  description  of  the  methods  used  for  graduating  these  measures 
would  not  be  out  of  place,  and  will  serve  to  explain  some  of  the 
variations  in  capacity. 
For  a  cheap  measure  the  lines  blown  or  molded  on  the  outside 
of  the  tumbler  are  the  ones  most  readily  available.  These  lines 
may  be  made  quite  heavy  and  distinct,  but  it  will,  necessarily,  be 
very  difficult,  if  not  well-nigh  impossible,  to  get  two  glasses  exactly 
alike,  on  account  of  the  variation  in  the  amount  of  glass  entering 
the  mold  and  the  consequent  difference  in  their  inner  capacity. 
This  type  of  glass  is  illustrated  by  numbers  io  and  II. 
The  next  has  the  marks  placed  on  the  inside  of  the  glass  by  a 
graduated  plunger.  If  the  plunger  is  accurately  graduated  this 
method  will  give  quite  uniform  results  for  the  same  lot  of  glasses. 
Numbers  12,  13  and  16  are  glasses  of  this  variety,  and  illustrate  the 
possible  variation  due  to  different  plungers.  These  glasses  also 
illustrate  the  fact  mentioned  a  few  moments  ago,  that  these  lines  are 
sometimes  very  faint  and  easily  obscured  by  a  dark  or  viscid  liquid. 
This  is  due  to  the  fact  that  the  plunger  cannot  be  deeply  engraved, 
as  this  would  interfere  with  its  consequent  withdrawal  from  the  fin- 
ished glass. 
Engraved  glasses  appear  to  be  graduated  according  to  one  of  the 
following  methods : 
Where  a  pressed  glass  is  used  for  graduation,  it  is  customary  for 
some  manufacturers  to  accurately  measure  and  graduate  one  glass 
as  a  sample  ;  from  this  they  graduate  a  wood  block,  and  this  block 
is  subsequently  used  as  a  pattern  to  graduate  the  remaining  glasses 
made  from  this  particular  mold.  Glasses  graduated  in  this  way 
seldom  vary  more  than  10  per  cent.  The  cause  of  variation  is  a 
slight  difference  in  the  internal  diameter  of  the  glass,  or  a  slight 
elevation  or  depression  of  the  bottom  of  the  tumbler  that  prevents 
the  gauge  block  from  going  to  its  proper  position.  Numbers  14,  15 
and  17  are  made  according  to  this  method,  and  are  fair  specimens 
of  the  results. 
The  next  method,  and  the  one  that  is  used  almost  exclusively  on 
the  higher  priced  glasses,  is  to  measure  into  a  glass  a  certain  quan- 
