134 
The  Metric  System  and 
/  Am.  Jour.  Pharm. 
February,  1918. 
not  by  a  direct  comparison  with  other  standards  of  the  same  names, 
derived  from  Great  Britain  or  elsewhere.  This  is  a  simple  metro- 
logical  fact.  The  international  metric  standards  today  represent 
with  greater  accuracy,  invariability,  and  interchangeability,  the  ab- 
stract or  ideal  units  of  length  and  mass  related  to  any  and  all  other 
units  of  length  or  mass  by  some  mathematical  ratio  than  do  any 
yard,  gallon,  or  pound,  or  other  standards.  In  other  words,  in  the 
present  condition  of  metrological  science  recourse  must  be  had  to  the 
metric  system  for  fundamental  standards  whatever  the  system  of 
measurement,  and  today  in  the  interest  of  precision  all  arbitrary 
standards  of  various  systems  must  be  defined  in  metric  units. 
Now  the  standards  and  the  definitions  prevailing  in  any  industry 
may  seem  to  the  ordinary  manufacturer,  producer,  or  builder,  very 
remote  from  his  daily  problems,  and  the  fundamental  standards  of 
a  system  of  weights  and  measures  may  be  close  to  the  vanishing 
point  in  the  perspective  of  the  worker,  but  it  must  be  impressed  that 
the  connection  must  be  maintained  unbroken,  and  that  where  there  is 
uncertainty  as  to  standards  or  where  there  is  variation,  accurate 
work  and  interchangeability  cannot  be  maintained.  Naturally  as  a 
process  becomes  more  general  and  universal,  the  exact  correspond- 
ence with  the  standard  grows  less,  but  interchangeability  is  secured 
so  long  as  proper  limits  of  tolerance  are  not  exceeded.  A  single 
standard  properly  defined  and  with  tolerance  limits  stated  makes  for 
complete  interchangeability  in  an  industry  or  product. 
It  may  be  objected,  that  in  the  foregoing  argument  the  order 
of  the  ordinary  industrial  process  has  been  reversed,  and  it  has 
been  sought  to  derive  standards  for  articles  in  common  use  from 
the  refined  fundamental  standards  of  the  scientists  which  possess 
a  theoretical  rather  than  practical  interest.  This  in  part  may  be 
admitted,  and  in  part  denied.  In  the  older  industries  where  there 
have  been  developed  policies  of  standardization,  this  standardiza- 
tion came  usually  as  a  result  of  temporary  needs  and  minimum 
adjustment,  secured  by  small  concessions  or  enforced  conforma- 
tion to  the  sizes  and  styles  of  one  or  more  large  manufacturers. 
In  some  industries  in  various  countries,  these  systems  have  been 
developed  with  care  and  have  served  local  or  national  needs.  Now 
it  is  inevitable  that  where  systems  have  developed  in  this  way,  they 
should  become  distinctly  national,  and  their  international  accept- 
ance is  conditioned  solely  by  the  foreign  trade  of  the  country  of 
their  origin.    As  a  result  when  several  of  these  systems  of  stand- 
