252  VERIFICATION  OF  CASTOR  OIL  AND  BALSAM  COPAIBA,  ETC. 
unsteady.  In  one  case  I  saw  a  gentleman  drop  the  liquid  from 
a  height  of  ten  or  twelve  inches.  I  may  also  remark  that  in 
the  case  of  fixed  oils,  it  is  of  no  use  placing  a  second  drop 
after  the  first  one  has  failed,  for  in  such  case,  the  second  drop 
either  simply  flattens,  or  in  the  case  of  some  essential  oils  pre- 
sents a  beautiful  example  of  the  spheroidal  condition  of  liquids 
at  ordinary  temperatures. 
With  some  other  volatile  oils  a  second  drop  will  displace  the 
film  formed  by  the  first  and  produce  a  second  cohesion  figure  on 
the  same  surface.  With  respect  to  the  ethers,  alcohol,  etc.,  it 
is  different  :  each  drop  forms  a  sharp  and  well-defined  figure, 
lasting  only  about  a  second,  and  hence  the  best  way  of  exhibit- 
ing such  figures  is  to  have  the  liquid  in  a  dropping-tube,  and 
allow  drops  to  fall  in  regular  succession  on  the  surface  of  the 
water,  by  which  means  a  regular  succession  of  figures  may  be 
kept  up  and  their  characters  studied.  Here  is  some  of  Dr. 
Morson's  creosote.  A  drop  placed  on  the  surface  of  two  ounces 
of  water  forms  a  highly  characteristic  figure,  sailing  about  with 
a  vibratory,  crispating  edge.  In  the  course  of  seven  minutes 
this  drop  becomes  gradually  disposed  of  by  solution ;  or  in 
other  words,  the  adhesion  of  the  water  completely  overcomes 
the  cohesion  of  the  liquid,  and  diffusion  spreads  it  through  the 
mass  of  the  liquid.  A  second  drop  may  now  be  placed  on  the 
same  surface.  It  exhibits  the  character  of  the  first  figure  in  a 
mitigated  form  ;  it  is  less  active ;  it  is  disposed  of  by  solution 
in  12i  minutes  ;  a  third  drop  is  disposed  of  in  25  minutes  ;  a 
fourth  drop  ceases  to  give  a  cohesion  figure  at  all  :  it  is  not 
disposed  of  after  110  minutes.  In  fact,  the  two  ounces 
of  water  are  saturated  :  that  is,  the  adhesive  force  of 
the  water  and  the  diffusibility  of  the  creosote  are  destroyed* 
Increase  the  quantity  of  water,  and  we  restore  the  adhe- 
sive force  and  diffusibility  in  proportion  to  the  quantity, 
and  the  struggle  between  the  water  and  the  creosote  sets  in 
again  with  the  characteristic  figure.  Here  is  a  specimen 
of  carbolic  acid.  The  figure  is  very  different  from  that  of  creo- 
sote, and  its  duration  is  very  much  less.  And  here  it  may  be 
noted  that  some  of  the  figures  of  oils,  etc.,  are  very  durable,  re- 
maining on  the  surface  for  hours ;  and  even  among  volatile  01I3 
