On  the  Action  of  Nuclei  on  a  Supersaturated  Solution.     205 
wave  is  reflected  under  such  circumstances  as  to  make  the  par- 
ticle-velocity at  the  point  of  reflection  greater  than  it  would  be 
if  the  wave  continued  to  be  transmitted  through  a  uniform  me- 
dium, the  incident  and  reflected  waves  will  be  of  opposite  phases  ; 
and  for  this  reason,  viz.  that  the  directions  of  transmission  of 
these  waves  being  opposite,  when  they  are  in  opposite  phases 
their  particle-velocities  will  coincide  in  direction,  and  vice  versa. 
The  bearing  of  this  principle  upon  the  undulatory  theory  of 
Newton's  rings  will  not  fail  to  be  adverted  to. 
6  New  Square,  Lincoln's  Inn, 
Februarv  5,  1S/2. 
XXIV.  On  the  Action  of  Nuclei  in  separating  Gas  or  Vapour 
from  its  Supersaturated  Solution.  By  Charles  Tomlinson, 
F.R.S* 
IN  the  Philosophical  Magazine  for  August  and  September 
1867,  and  in  the  Proceedings  of  the  Royal  Society  for 
1868-69  (p.  248),  are  two  papers  by  me,  on  the  Action  of  Nuclei 
in  separating  Gas  from  Soda-water  &c,  and  Vapour  from  Liquids 
at  or  near  the  boiling-point.  In  compliance  with  a  request  of 
the  Abbe  Moigno,  I  furnished  him  with  an  account  of  these  two 
papers  for  insertion  in  Les  Mondess  in  which  they  appeared  in 
the  Numbers  for  the  12th  of  October  and  the  2nd  of  November 
last.  In  the  Number  for  the  21st  of  December  last,  the  Rev. 
P.  Sauna  Solaro,  S.J.,  has  made  some  critical  remarks  on  these 
two  papers,  in  which  I  endeavour  to  trace  the  action  of  nuclei  in 
separating  gas  and  vapour  from  their  supersaturated  solutions, 
although  the  remarks  in  question  are  chiefly  confined  to  the  se- 
paration of  vapour. 
I  may  remark  that  the  term  "  gaseous  supersaturated  solu- 
tion "  refers  to  such  liquids  as  soda-water,  Seltzer  water,  and 
champagne  j  and  seeing  that,  in  a  large  number  of  cases  in  which 
nuclei  separated  gas  from  them,  there  was  a  precisely  similar 
action  of  nuclei  in  separating  vapour  from  liquids  at  or  near  the 
boiling-point,  it  seemed  not  unreasonable  to  suppose  that  these 
last-named  liquids  are  constituted  like  the  former.  Moreover  in 
both  cases  the  received  opinion  is  that  nuclei  act  by  carrying 
down  air,  into  which  the  gas  or  the  vapour  is  said  to  expand, 
and  so  escape;  whereas,  according  to  my  theory,  I  endeavour 
to  show  that  as  gas  or  vapour  will  adhere  to  an  oily,  fatty,  or 
greasy  body,  or  to  a  body  that  has  been  handled,  while  water 
will  not  so  adhere,  it  is  only  necessary  to  introduce  such  a  body 
into  the  solution  to  see  that  it  becomes  immediately  covered  with 
bubbles  of  gas  or  of  vapour.  These  bubbles  escape  from  its  sur- 
*  Communicated  by  the  Author. 
