WHY  BEES  WORK  IN  TIIE  DARK. 
319 
Indigo  may  be  valued  in  the  following  way; — In  a  well- 
closed  glass  bottle,  finely  powdered  indigo  is  reduced  by  means 
of  potash  or  lime  and  a  protosalt  of  iron,  under  a  layer  of  min- 
eral oil.  When  the  precipitate  has  completely  deposited,  a 
certain  volume  of  the  clear  solution  of  indigo-white  is  removed 
by  means  of  a  pipette,  care  being  taken  that  a  layer  of  oil 
swims  on  the  surface  of  the  solution.  The  pipette  is  then 
emptied  into  the  absorption  bottle,  which  must  also  contain  oil, 
and  the  shaking  is  continued  until  the  indigo  blue  is  re-formed. 
According  to  theory,  8  parts  by  weight  of  combined  oxygen 
answer  to  131  parts  of  indigo  blue;  or,  for  one  gramme  of  in- 
digo blue  45-7  c.c.  of  oxygen  at  20°C.  are  required.  From 
these  numbers  we  may  see  at  once  what  degree  of  accuracy 
this  way  of  analysing  indigo  promises. — Journ.  fur  Prdkt. 
Qhem.r  from  Cliem.  Ntws,  London,  May,  1864. 
WHY  BEES  WORK  IN  THE  DARK. 
A  lifetime  might  be  spent  in  investigating  the  mysteries 
hidden  in  a  bee-hive,  and  still  half  of  the  secrets  would  be  un- 
discovered. The  formation  of  the  cell  has  long  been  a  celebra- 
ted problem  lor  the  mathematician,  whilst  the  changes  which 
the  honey  undergoes  olfer  'at  least  an  equal  interest  to  the 
chemist.  Every  one  knows  what  honey  fresh  from  the  comb  is 
like.  It  is  a  clear  yellow  syrup,  without  a  trace  of  solid  sugar 
in  it.  Upon  straining,  however,  it  gradually  assumes  a  crystal- 
line appearance — it  candies,  as  the  saying  is— and  ultimately 
becomes  a  solid  mass  of  sugar.  It  has  not  been  suspected  that 
this  change  was  a  photographic  action.  That  the  same  agent 
which  alters  the  molecular  arrangement  of  the  iodide  of  silver 
on  the  excited  collodion  plate,  and  determines  the  formations  of 
camphor  and  iodine  crystals  in  a  bottle,  causes  the  syrupy  honey 
to  assume  a  crystalline  form.  This,  however,  is  the  case.  M. 
Bcheibler  has  enclosed  honey  in  stoppered  flasks,  some  of  wrhich 
he  has  kept  in  perfect  darkness,  whilst  others  have  been  ex- 
posed to  the  light.  The  invariable  result  has  been  that  the 
sunned  portion  rapidly  crystallises,  whilst  that  kept  in  the  dark 
has  remained  perfectly  liquid.    We  now  see  why  bees  are  so 
