316  Intelligence  and  Miscellaneous  Articles, 
northern  escarpment  of  the  Atlas  plateau,  and  of  great  moraines  at 
the  heads  of  the  valleys  of  the  Atlas,  both  of  which  he  ascribed  to 
glacial  action.  An  elevation  of  the  coast  line  of  at  least  70  feet  was 
indicated  by  raised  beaches  of  concrete  sand  at  Mogador  and  else- 
where ;  and  the  author  considered  that  a  slight  subsidence  of  the 
coast  was  now  taking  place.  The  surface  of  the  plain  of  Marocco 
was  described  as  covered  with  a  tufaceous  crust,  probably  due  to  the 
drawing  up  of  water  to  the  surface  from  the  subjacent  calcareous 
strata  and  the  deposition  from  it  of  laminated  carbonate  of  lime. 
XXXIX.  Intelligence  and  Miscellaneous  Articles. 
AN  EXPERIMENT    IN    REFERENCE    TO    THE    QUESTION    AS    TO    VA- 
POUR-VESICLES.      BY  T.  PLATEAU. 
TpROM  a  research  of  M.  Duprez*,  it  is  known  that  when  a  vessel 
■*-  of  water  is  inverted  with  the  opening  downwards,  it  is  not  ne- 
cessary that  this  opening  be  very  narrow  for  the  water  to  remain 
suspended.  M.  Duprez  kept  water  suspended  in  a  vertical  tube 
which  was  nearly  20  millims.  in  internal  diameter. 
Assuming  now  that  when  water  is  hanging  in  such  a  tube  with 
the  surface  downwards  a  small  hollow  air-bubb!e  is  brought  into  con- 
tact with  this  surface,  the  air  in  it,  in  virtue  of  the  pressure  of  the 
envelope,  will  immediately  penetrate  into  the  interior  of  the  liquid, 
and  will  rise  in  it  in  virtue  of  the  smaller  specific  gravity.  This  I 
have  confirmed  by  means  of  an  experiment.  I  took  a  small  glass 
tube  of  about  4  millims.  diameter  in  the  clear,  drew  it  out  at  one 
end  to  an  aperture  of  about  0'4  millim.  diameter,  and  closed  the 
wider  end  by  a  cork  coated  with  grease.  By  touching  the  drawn- 
out  end  with  a  piece  of  filtering  paper,  which  was  soaked  with  dis- 
tilled water,  I  succeeded  in  bringing  into  the  narrow  aperture  a 
column  of  this  liquid  not  more  than  a  millimetre  in  length.  By 
carefully  depressing  the  cork,  a  hollow  bubble  is  seen  to  form  at  the 
drawn-out  aperture,  which  may  have  a  diameter  of  less  than  a  mil- 
limetre, and  usually  lasts  seven  or  eight  seconds.  In  this  operation 
the  wider  part  of  the  tube  must  be  covered  with  several  layers  of  a 
non-conducting  material  in  order  to  eliminate  the  influence  of  the 
warmth  of  the  fingers.  After  having  thus  acquired  the  power  of 
procuring  very  small  hollow  bubbles,  water  was  suspended  in  a  tube 
kept  vertical  by  a  suitable  stand.  The  internal  diameter  of  this 
tube  was  only  a  centimetre ;  and  with  such  a  small  diameter  the 
suspension  is  very  easy.  It  is  only  necessary,  after  filling  the  tube 
with  water  and  closing  the  mouth  with  a  piece  of  paper,  to  invert  it 
and  then  draw  the  paper  aside  to  get  a  free  surface  ;  a  hollow  water 
bubble  of  less  than  a  milimetre  diameter  is  then  produced  as  described 
above,  and  brought  to  the  free  surface  of  the  suspended  water. 
When  they  are  in  contact,  the  bubble  detaches  itself  from  the  drawn- 
*  "  Mem.  sur  un  cas  particulier  de  l'equilibre  des  liquides,"  Mem.  de 
VAcad4mie  Roy.  de  Belgique,  vol.  xxvi.  1851,  and  xxviii.  1854. 
