428  Mr.  R.  W.  Atkinson's  Examination  of  the 
occulted,  yet  the  above-mentioned  appearance  seems  to  prove  its 
existence. 
2nd.   As  to  the  enlarged  appearance  of  the  moon  in  the 
horizon. 
Let  the  smaller  semi- 
circle E   represent   the 
earth.      On  the  larger 
semicircle  draw  two  small 
lines,  A  and  B,  of  equal 
length,  for  the  diameter 
of  the  moon  at  two  dif- 
ferent altitudes.     From 
the  extremities  of  these 
small  lines  draw  conver- 
ging lines  to  the  eye  of  the  spectator  on  the  earth's  surface.    Now 
the  astronomer,  measuring  the  moon's  diameter  with  his  qua- 
drant, finds  that  the  moon  in  the  horizon  at  A  is  smaller  than  the 
moon  at  B,  as  might  be  expected,  because  it  is  further  off;   but 
to  the  naked  eye  it  always  appears  the  larger  of  the  two.     This, 
I  think,  may  be  explained  by  remarking  that  on  a  fine  night  the 
vault  of  heaven  never  appears  like  half  a  globe,  but  is  very  much 
flattened  over  head.     The  effect  of  the  atmosphere  is  to  make 
the  stars  in  the  zenith  seem  nearer  to  us  than  the  stars  in  the 
horizon.     Let  us  draw  such  a  flattened  vault  within  our  larger 
semicircle,  and  the  small  arcs  a  and  b,  intercepted  by  the  lines 
drawn  from  A  and  B  to  the  spectator's  eye,  will  now  represent 
our  two  moons  on  the  apparent  vault  of  heaven.     Of  these  it 
will  be  seen  that  a,  the  moon  near  the  horizon,  is  larger  than 
b}  the  moon  at  a  higher  altitude,  agreeably  with  the  appearance 
in  the  heavens. 
Yours  obediently, 
32  Highbury  Place,  Samuel  Shaupe. 
13th  May,  1872. 
LIII.  An  Examination  of  the  recent  attack  upon  the  Atomic 
Theory.  By  R.  W.  Atkinson,  F.C.S.}  Assistant  in  the  Che- 
mical Laboratory,  University  College*. 
A  SHORT  time  ago  a  paper  was  read  by  Dr.  Wright  before 
the  Chemical  Society,  and  subsequently  appeared  in  the 
April  Number  of  the  Philosophical  Magazine,  entitled  IC  On  the 
Relations  between  the  Atomic  Hypothesis  and  the  Condensed 
Symbolic  Expressions  of  Chemical  Facts  and  Changes  known  as 
*  Communicated  by  the  Author. 
