341       REMARKS  ON  THE  COHESION  FIGURES  OF  LIQUIDS. 
gently  delivered  to  the  surface  of  sulphuric  acid  from  the  end 
of  a  pipette,  flattens  down  into  a  well-defined  disk  about  the  size 
of  a  shilling,  marked  with  radial  lines;  these  disappear  at  the 
centre,  while  fragments  remain  for  some  seconds,  near  the  cir- 
cumference. Alcohol,  ether,  benzole,  etc.,  on  sulphuric  acid 
give  striking  figures,  showing  how  remarkable  is  the  change 
when  the  adhesive  force  of  the  surface  is  varied  by  the  substitu- 
tion of  some  other  liquid  for  water. 
When  acetic  acid  is  used  as  the  adhesive  surface,  a  new  set 
of  figures  is  obtained.  Thus,  oil  of  camphor,  which  on  water 
forms  a  large  well-developed  film,  produces  only  a  small  disk  on 
acetic  acid  (sp.  gr.  1-045),  which  disk  sails  about  with  consider- 
able agitation,  throwing  off  numerous  globules.  Oil  of  lavender 
also  forms  a  small  disk,  which  gathers  itself  up  with  strange  con- 
tortions, and  illustrates  in  its  own  way  the  struggle  that  is  go- 
ing on  between  cohesion  and  adhesion. 
A  question  was  also  asked  respecting  cod-liver  oil,  when  I 
stated  that  a  specimen  (A),  supplied  to  me  as  pure,  gave  a  cer- 
tain figure ;  that  a  specimen  (B)  purchased  at  a  shop  gave 
another  figure;  but  that  on  mixing  two-thirds  of  common  fish 
oil  with  one-third  of  A,  I  obtained  a  figure  almost  identical  with 
that  given  by  B. 
The  first  in  the  accompanying  page  of  engravings  is  a  portion 
of  the  figure  of  castor  oil.  Of  course  it  will  be  understood  that 
all  these  figures  are  complete  disks  or  circles,  of  which  portions 
only  are 'here  represented.  They  are  produced  on  the  surface 
of  water  contained  in  a  shallow  glass  about  four  inches  in 
diameter.*  The  following  experiments  were  made  on  the  10th 
and  11th  of  March  in  these  new  glasses.  They  were  not  made 
under  very  favorable  circumstances,  as  the  temperature  of  the 
room  was  under  50°  ;  whereas  it  should  not  have  been  less  than 
*  I  have  lately  ordered  a  number  of  glasses  resembling  large  claret- 
glasses  ;  each  glass  stands  on  a  wide  foot,  and  the  stem  is  rather  long,  for 
the  convenience  of  handling ;  so  that  the  hand  need  never  be  brought 
into  contact  with  the  inner  surface  of  the  glass.  After  an  experiment,  a 
jet  of  water  from  a  tap  will  often  get  rid  of  all  traces  of  the  oil  of  a  former 
experiment.  Should  it  not  do  so,  the  caustic  potash  solution  must  be 
used;  and  should  this  fail,  sulphuric  acid  must  be  resorted  to.  A  glass  is 
left  at  the  Society's  house,  for  inspection  by  members. 
