360  Development  of  the  Chemical  Arts.  {^"^2^Z'S^t''^' 
Latin  verbs.  Then  let  him  learn  and  store,  by  lecture  courses,  by 
printed  books,  by  laboratory  work,  by  experiment,  by  field  excursions^ 
by  conversation,  friendship,  and  sparingly  by  scientific  meetings. 
Quickly  comes  the  second  stage — the  time  ripe  for  classification  ;  then^ 
and  not  before,  the  mode  of  learning  changes,  not  the  act,  and  the 
task  before  the  learner  is  to  investigate  his  stores.  Let  him  boldly 
take  his  accumulated  rough  or  neatly  copied  memoranda,  and  consign 
them  to  oblivion  ;  and  with  his  better  knowledge  and  acquired  exper- 
ience let  him  work  out  his  own  digest  of  things  worthy  of  remem- 
brance. Plan  there  must  be,  for  the  mind  cannot,  without  superhuman 
effort,  recollect  a  mass  of  miscellaneous  facts  ;  and  plan  there  must  be 
if  the  third  stage,  that  of  practical  application,  is  to  be  attained. 
May  we  not  say  with  truth  that  it  is  on  the  right  use  of  this  second 
period  that  the  future  hangs  ?  May  we  not  say  that  the  more  the  facts 
and  the  greater  the  storage,  the  better  and  more  philosophic  will  be  the 
summary  ?  May  we  not  add,  that  where  in  youth  there  has  been  this 
storage,  and  subsequent  orderly  arrangement,  we  may  predict  with 
confidence  a  successful  present  issue,  and  an  awakened  pleasure  in 
these  pursuits  such  as  is  destined  to  endure. —  The  Chemist  and  Drug- 
gist^ (London^  June  15,  1875. 
REPORT  OF  THE  DEVELOPMENT  OF  THE  CHEMICAL  ARTS 
DURING  THE  LAST  TEN  YEARS  * 
BY   DR.   A.   W.  HOFMANN. 
The  Elements  of  Water. \    By  Dr.  A.  Oppenheim. 
Oxygen. — Like  the  evolution  of  human  life,  the  development  of 
every  chemical  art  is  connected  with  oxygen.  Directly  or  indirectly^ 
it  intervenes  in  every  manufacturing  operation.  With  equal  necessity,, 
life  and  technology  derive  it  from  that  exhaustless  source  of  all  being,, 
the  atmosphere.  Furthermore,  no  discovery  has  had  a  greater  signif- 
icance for  the  history  of  culture  than  that  of  the  material  nature  of  the 
air,  and  the  discovery — the  centenary  of  which  we  commemorate  this, 
year — of  its  most  important  constituent,  oxygen  gas. J    To  the  same 
*  Berichte  liber  die  Entwickelung  der  Chemischen  Industrie  wahrend  des. 
letzten  Jahrzehends."" 
f  "Die  Eleniente  des  Wassers." 
%  "  On  the  I  St  of  August,  1774,  I  endeavored  to  extract  air  from  mercurius  prae- 
cipitatus  per  se." — Joseph  Priestley,  "  Experiments  and  Observations  on  Air,"  ii, 
106     See  also  Kopp,  "  Geschichte  der  Chemie,"  iii,  200  and  204. 
