266 
NOTE  ON  CARBOLIC  ACID,  ETC. 
less  definite  as  to  the  degree.  All  that  can  be  considered  as 
proved  is  that  the  cresol  has  more  than  double  the  azymotic 
power  of  the  Phenol  in  its  application  to  these  mosses ;  but  how 
much  more  than  double  is  not  shown.  In  searching  for  a  more 
sensitive  mode  of  comparison,  the  smell  and  taste  were  finally 
adopted,  but  as  it  was  soon  proved  that  the  smell  was  far  less  deli- 
cate than  the  taste,  the  latter  alone  was  relied  upon.  The  taste 
of  the  two  is  very  different.  That  of  the  Phenol  is  characterized 
by  its  sweetness  and  comparative  blandness.  That  of  the  cresol 
is  smoky,  dry  as  opposed  to  sweet,  and  pungent,  and  is  not  instant- 
ly developed.  In  very  dilute  solution  the  latter  has  only  a  smoky 
taste.  In  these  trials  by  taste  it  was  soon  found  to  be  necessary 
to  consult  a  number  of  persons  quite  independently  of  each  other, 
and  also  to  have  some  criterion  or  test  of  the  delicacy  of  different 
tastes,  so  as  to  exclude  those  which  were  not  tolerably  sensitive, 
and  it  was  very  curious  and  instructive  to  see  how  this  sense  varies 
in  different  persons.  Solutions  of  common  ethyl-alcohol  were  fixed 
upon  for  this  test,  and  it  was  found  that  comparatively  few  persons 
could  recognize  a  mixture  of  one  part  common  alcohol  in  ten 
thousand  parts  of  distilled  water  ;  but  that  many  would  promptly 
detect  one  part  in  five  thousand.  This  test  served  well  in  se- 
lecting the  tastes  to  be  relied  upon,  and  in  no  single  instance 
did  cross-examination,  by  change  and  confusion  of  bottles,  and 
other  efforts,  succeed  in  materially  changing  or  interfering  with 
the  decisions  made.  Ten  persons  beside  the  writer  were  selected 
from  many  tried,  and  their  evidence  was  accepted  in  the  follow- 
ing results.  Four  of  these  proved  upon  repeated  trials  to  ex- 
ceed the  others  in  delicacy  of  taste,  and  two  were  quite  sensitive, 
making  their  decisions  with  great  promptitude  and  certainty. 
These  were  repeatedly  tried,  not  only  upon  their  own  con- 
clusions, but  were  used  to  test  the  conclusions  of  others,  and  the 
different  trials  were  made  upon  different  days ;  extended  over  a 
period  of  many  days,  and  were  often  made  early  in  the  morn- 
ing, when  the  senses  are  fresh  and  impressible,  and  before  the 
odors  of  a  laboratory  had  blunted  the  perceptions  of  those  occu- 
pied in  it.  A  series  of  preliminary  experiments  and  observa- 
tions were  made  by  which  to  learn  how  to  conduct  them,  and  how 
best  to  avoid  the  many  chances  of  inaccuracy  and  fallacy.  The 
solutions  used  were  made  with  great  care  and  accuracy  from  the 
