THE  PRESENCE  OF  IODINE  IN  VARIOUS  PLANTS. 
65 
quent,  whilst  the  proportion  of  iodine  in  the  atmosphere  is  only 
one  tenth  of  that  in  the  neighborhood  of  Paris,  where  these  diseases 
rarely  exist.  The  interest  and  importance  of  Mr.  Chatin's  state- 
ments, should  they  be  corroborated,  induced  Mr.  Macadam  to  in- 
vestigate the  subject  as  regards  Scotland  both  in  relation  to  the 
atmosphere  and  the  plants. 
He  commenced  with  the  atmosphere;  he  caused  the  air  to  traverse, 
1st,  a  tube  containing  slips  of  starch  paper ;  2d,  a  two  necked  gas- 
bottle  containing  about  3  ounces  of  a  solution  of  caustic  soda, 
during  several  hours  of  the  morning,  and  the  process  continued  in 
the  afternoon  with  a  solution  of  caustic  potash.  The  starch  papers 
did  not  exhibit  the  slightest  coloration  even  when  moistened;  the 
solutions  of  potash  and  soda,  however,  on  being  treated  with  starch 
and  nitric  acid,  at  once  exhibited  the  rose  colored  characteristic  of 
the  presence  of  iodine  in  small  quantity.  When,  however,  portions 
of  the  alkaline  solutions  not  subject  to  the  action  of  the  air  were 
tested,  the  same  evidence  of  iodine  was  obtained.  Hence,  the  ne- 
cessity of  a  new  experiment  to  guard  against  this  difficulty. 
He  now  passed  the  air  through  a  tube  filled  with  slips  of  damp 
starch  paper ;  then  through  a  gas  bottle  immersed  in  a  freezing 
mixture;  and  lastly  a  gas  bottle  containing  a  solution  of  nitrate  of 
silver.  A  continuous  current  of  air  was  drawn  through  this  arrange- 
ment during  five  hours,  commencing  at  mid-day.  At  the  conclusion, 
the  papers  were  not  altered  in  the  slightest  degree  :  the  first  gas 
bottle  contained  a  quarter  of  an  ounce  of  liquid,  which  gave  no 
evidence  of  iodine  to  the  most  delicate  tests,  and  the  solution  of 
silver  had  not  been  apparently  changed,  and  did  not  give  evidence 
of  the  slightest  trace  of  iodine  on  the  application  of  the  most  rigid 
tests. 
The  failure  of  these  experiments,  which  were  made  at  different 
heights  on  Arthur's  Seat,  led  Mr.  Macadam  to  make  a  more  ex- 
tended and  complete  trial  at  the  Kinneil  Iron  Works  at  Borrow- 
stowness,  where  the  proprietor  kindly  offered  every  facility,  by  al- 
lowing the  author  to  attach  his  apparatus  to  the  blowing  machine 
furnishing  the  blast  to  the  furnaces  under  great  pressure.  Under 
these  circumstances  a  rapid  current  of  air  was  passed  through  a 
tube  with  starched  paper ;  a  condensing  worm  cooled  by  a  freezing 
mixture  and  attached  to  a  receiver,  a  tall  jar  containing  chips  of 
6* 
