Prof.  M.  B.  Pell  on  the  Constitution  of  Matter.         163 
Clausius  and  Maxwell, helps  us  somewhat.  This  theory  maybe 
regarded  as  established,  and  as  forming  the  most  important 
addition  which  has  been  made  to  our  real  knowledge  of  the  laws 
of  inorganic  matter  in  this  generation.  Maxwell,  for  reasons 
assigned,  assumes  that  the  gaseous  molecules  repel  one  another 
according  to  a  certain  law  which  makes  the  force  insensible,  ex- 
cept at  very  small  distances.  The  theory  of  elastic  molecules 
involves  a  similar  assumption ;  for  the  elasticity  of  the  molecules 
must  be  caused  by  a  repulsive  action  between  their  atoms,  unless 
we  are  to  accept  an  elastic  molecule  as  a  finality,  beyond  which 
our  inquiries  into  the  nature  of  matter  cannot  extend.  The  con- 
densible  gases  and  vapours  so  closely  resemble  the  permanent 
gases  in  so  many  of  their  properties,  that  it  is  impossible  not  to 
believe  that  they  are  governed  by  the  same  laws.  If  the  mole- 
cules of  hydrogen  repel  one  another  at  certain  distances,  we  can- 
not doubt  that  the  same  is  true  with  respect  to  chlorine,  and 
carbonic  acid  gas,  and  steam.  Indeed  it  would  be  difficult  to 
know  where  to  draw  the  line  between  hydrogen  and  the  most 
refractory  solid.  But  if  the  molecules  of  carbonic  acid  gas.be 
brought  near  enough  together,  they  undoubtedly  attract,  and  at 
still  shorter  distances  again  repel  one  another.  If  we  assume  the 
existence  of  isolated  atoms,  there  seems  no  escape  from  the  doc- 
trine of  an  alternation  of  actual  attractions  and  repulsions. 
Sir  Humphry  Davy  supposed  that  the  repulsive  forces  between 
the  particles  of  matter  might  be  of  a  nature  analogous  to  that 
which  keeps  the  planets  from  falling  into  the  sun,  or  to  what 
commonly  goes  by  the  name  of  centrifugal  force.  Except  that 
this  view  of  the  case  is  mentioned  with  approval  by  a  recent 
writer,  I  should  not  have  thought  it  necessary  to  make  use  of 
any  arguments  to  show  that  the  complicated  actions  which  take 
place  between  particles  of  matter  cannot  be  accounted  for  by 
Newton's  law  of  attraction  alone.  That  the  particles  of  a  solid  body 
should  be  not  only  kept  apart,  but  in  permanent  general  relative 
positions,  by  centrifugal  force  alone,  seems  to  me  utterly  incon- 
ceivable under  any  known  mechanical  laws.  It  may  be  demon- 
strated moreover,  assuming  the  theory  of  atoms,  that  the  cohe- 
sive forces  of  any  substance,  having  any  appreciable  tenacity,  are 
not  only  greater,  but  many  millions  of  times  greater  than  what 
would  be  caused  by  Newton's  law.  It  is  so  far  certain,  then, 
that  that  law  is  not  absolutely  universal,  but  is  replaced  or  sup- 
plemented by  something  totally  different  at  very  short  distances. 
The  atoms  or  particles  of  a  solid  body  certainly  seem  to  be  in 
a  position  of  stable  equilibrium,  or  rather  to  be  vibrating  about 
such  a  position;  and  there  seems  no  good  reason  for  doubting 
that  such  is,  not  apparently  only,  but  really  the  case.  The  fol- 
lowing considerations  seem  to  me  to  show  conclusively  that  it 
M2 
