VARIETIES. 
87 
all  participation  in  the  view,  which  he  called  an  "  exageration  outree  de  sa 
theorie." 
For  some  time  Laurent  was  alone ;  but  after  a  while  his  time  of  triumph 
came.  The  theory  was  then  attributed  wholly  to  him.  But  the  note  pub- 
lished by  Dumas  in  the  Annales  de  Chimie  et  de  Physique,  dispels  all 
doubts,  and  leads  to  justice  being  rendered  to  each  of  the  two  chemists,— 
to  Dumas  who  opened  the  way,  and  to  Laurent  who  established  the  theory 
and  rendered  it  of  practicable  value. — Am.  Journ.  of  Science  and  Arts. 
Electric  Illumination. — We  have  spoken  of  the  experiments  in  electric 
illumination  made  at  Lyons  by  Lacassaigne  and  Thiers.  They  have  con- 
tinued their  trials  with  great  success,  and  through  the  month  of  March 
lighted  one  of  the  principal  streets  of  Lyons,  between  the  hours  of  seven 
to  eleven.  Two  pieces  of  apparatus  set  up  at  the  extremities  of  the  street 
upon  a  frame  crossing  between  the  roofs  of  the  opposite  houses,  sent  their 
beams  down  the  middle  of  the  street.  The  gas  was  not  lit ;  all  the  illumin- 
ation was  obtained  from  the  battery.  The  Rue  Imperial  is  about  550  yards 
long,  and  is  lighted  with  more  than  forty  jets  of  gas  ;  and  yet,  the  gas  light 
was  fully  replaced  by  the  electric  light.  Something  still  remains  to  be 
done.  It  is  important  that  the  light  should  come  from  a  much  greater 
height,  that  it  may  be  more  diffused,  and  less  blinding  and  fatiguing  to  the 
sight. — Ibid. 
Atmospheric  Electricity.  Theory  of  thunder. — Among  the  theories  of 
thunder,  the  recent  one  of  M.  Jobard,  Director  of  the  Museum  of  Industry 
of  Brussels,  should  be  counted  ;  it  may  be  called  the  chemical  theory. 
According  to  it,  thunder  is  nothing  but  the  detonation  of  a  detonating 
mixture  of  hydrogen  gas,  more  or  less  carburetted,  along  with  atmospheric 
air.  The  gas  comes  from  decomposing  organic  matters  and  goes  up  in 
"  pluies  ascendants."  Moreover,  he  assumes  that  the  same  gas  sustains 
the  clouds,  the  water  vesicles  being  filled  with  it.  M.  Jobard's  fertile 
mind  is  so  pressed  with  making  theories  for  every  thing,  that  it  does  not 
give  time  for  verifying  them.  He  gets  rid  of  the  hydrogen  again  by  sup- 
posing it  to  form  water ;  and  also  ammonia  with  the  nitrogen  of  the  air. — 
Ibid. 
Chemical  characteristics  of  Pure  Glycerin. — According  to  Dr.  Cap,  pure 
glycerin,  suitable  for  medicinal  purposes,  should  have  the  following  pro- 
perties :  It  should  be  odorless,  even  when  rubbed  between  the  hands  ;  its 
consistency  must  be  that  of  thick  syrup.  It  must  be  of  honey-like  taste, 
strongly  sweet,  its  reaction  nearly  neutral ;  one  volume  of  glycerin  must 
be  perfectly  soluble  in  one  volume  of  alcohol,  acidulated  with  l\m  of  sul- 
phuric acid,  without  forming  a  deposit,  when  standing  in  a  cool  place,  even 
after  twelve  hours.  Further:  1  volume  of  glycerin  must  dissolve  in  two 
volumes  of  a  mixture  of  100°|0  alcohol  and  50  !0  of  sulphuric  acid  without 
