VARIETIES.  181 
work,  although,  in  1843,  Dumas,  then  President  of  the  Academy  of  Science, 
obtained  from  the  Minister  of  Public  Instruction  permission  that  the  pub- 
lication should  be  made  at  the  expense  of  the  department.  It  was  not  till 
1861  that  his  plan  began  to  be  executed  ;  three  volumes  have  appeared  ; 
the  fourth  is  in  the  press  ;  this  will  be  followed  by  two  others,  treating  of 
questions  on  administration,  agriculture,  political  economy,  &c. 
Lavoisier  was  a  complete  man.  He  was  not  only  remarkable  as  a  chem- 
ist and  physicist;  he  was  an  administrator  of  no  ordinary  merit.  This  is 
evident  in  the  papers  which  he  has  left,  and  which  will  appear  with  the 
series  of  unpublished  documents  that  Dumas  has  collected  in  part  from  the 
family  of  Lavoisier,  and  in  part  from  notes  made  by  this  unfortunate  sa- 
vant during  his  journeys,  which,  as  well  as  his  laboratory  notes  and  other 
papers,  were  happily  preserved,  they  having  been  long  in  the  hands  of 
Arago,  to  whom  they  were  confided  by  the  daughter  of  Lavoisier. —  Corres- 
pondence of  Prof.  Nickles,  in  Silliman's  Journal. 
Magnesium  Light. — The  remarkable  properties  of  magnesium  light  are 
now  familiar  to  all.  (See  this  Jour.,  xl.  287.)  Some  facts  have  been  re- 
cently observed  that  are  not  yet  generally  known.  As  regards  its  chemi- 
cal effects,  this  light  is  well  fitted  to  render  luminous  phosphorescent  bodies, 
as  was  fully  ascertained  by  Mr.  Chautard  in  the  month  of  January,  1865. 
This  is  now  a  lecture-room  experiment.  Take  a  series  of  wide  tubes  en- 
closed in  a  box  and  filled  with  phosphorescent  substances.  All  these  tubes 
are  white;  but  when  struck  by  the  magnesium  light  each  becomes  phos- 
phorescent, taking  its  own  special  color.  About  a  year  since,  also,  Mr. 
Lallemand  discovered  that  a  mixture  of  chlorine  and  hydrogen  will  explode 
under  the  influence  of  magnesium  light;  and,  moreover,  that  this  explo- 
sion does  not  take  place  in  darkness,  nor  under  the  influence  of  the  red  or 
yellow  rays,  as  had  already  been  remarked  for  common  light  by  Gay  Lus- 
sac  and  Thenard. 
Magnesium  ignites  even  in  the  vapor  of  water,  when  it  is  brought  in 
contact  with  it  in  a  tube  containing  magnesium  heated  over  an  alcohol 
lamp  ;  the  metal  burns  with  brilliancy,  disengaging  the  hydrogen.  Un- 
der the  same  circumstances  zinc  will  not  burn  except  at  a  much  higher 
temperature.  This  observation  has  just  been  made  by  Messrs.  Deville  and 
Caron  ;  these  chemists  satisfied  themselves  that  magnesium,  when  cold, 
decomposes  water  in  the  presence  of  the  feeblest  acids,  even  of  carbonic 
acid. 
If  this  metal  were  not  so  expensive  its  light  could  be  applied  to  numer- 
ous uses.  A  recent  invention  of  an  Italian,  Mr.  Carlevaris,  may  perhaps 
prove  to  be  a  successful  application  of  it.  In  place  of  the  metal,  he  takes 
the  chloride  of  magnesium,  which  he  exposes  to  a  jet  of  ordinary  illumina- 
ting gas  and  atmospheric  air  with  a  tenth  part  of  oxygen.  The  light  thus 
produced  is  very  brilliant  and  appears  to  answer  admirably  for  the  pro- 
duction of  photographic  images,  or  for  magnifying  them. 
