NEW  ELECTRICAL  MACHINE. 
345 
for  immediate  publication.  The  writer,  however,  now  kindly 
sends  us  further  information  on  the  subject,  which  is  of  great 
value.  We  have  only  to  add  that  a  machine  on  this  principle 
was  exhibited  at  the  last  soiree  of  the  President  of  the  Royal 
Society,  and  attracted  much  attention. 
To  the  Editor  of  the  Chemical  News : 
Sib,  : — The  only  additional  information  which  I  am  able  at 
present  to  supply  on  the  subject  of  the  electricity  of  wood  has 
reference  to  the  different  capacity  of  different  kinds  of  wood  of 
being  converted  into  electrics,  and  here  I  would  caution  any  one 
who  may  feel  tempted  to  repeat  the  experiment  to  bear  in  mind 
that  though  it  be  true  that. every  kind  of  wood  which  I  have  yet 
examined  would  appear  capable,  more  or  less,  of  this  conversion, 
yet  that  time  is  a  singular  and  indispensable  condition  of  this 
transformation,  and  that  wood  can  no  more  be  rendered  "  elec- 
tric "  by  holding  it  to  the  fire  for  "  a  minute  or  two,"  than  toast 
is  dried  because  it  happens  to  be  colored.  It  requires  "  doing," 
like  meat ;  and  I  never  think  of  giving  less  than  from  one  to 
two  hours.  And  not  only  does  it  take  some  time,  but,  in  general, 
a  strong  heat  as  well ;  and  as  for  tulip  wood,  and  perhaps  one 
or  two  other  very  hard  woods,  they  obstinately  refuse  to  become 
electric  for  whole  hours.  After  three  hours,  no  change  could 
be  perceived,  till  at  length,  between  four  and  five  hours,  of  a  tem- 
perature just  short  of  actual  carbonization,  this  variety  then 
gave  pretty  strong  sparks,  and  retains  its  power  well. 
The  following  are  among  the  specimens  of  wood  which  I  have 
as  yet  examined,  though,  doubtless,  there  may  be  many  more 
that  might  with  advantage  be  submitted  for  trial : — Pine,  white 
deal,  mahogany,  cedar,  English  oak,  box,  English  birch,  Hun- 
garian ditto,  ebony,  satin,  white  holly,  pear,  rose,  tulip,  purple 
wood  and  king  wood;  likewise,  "pencil  cedar,"  American  wal- 
nut, English  ditto,  Japanese  oak,  common  elm,  (witch  elm,) 
partridge  wood,  (heart  and  sap,)  birds'  eye  maple,  sycamore, 
acacia,  yew,  lime,  sweet  chestnut,  horse  chestnut,  lignum  vitse, 
(heart  and  sap,)  cocoa,  black  thorn,  "  Amboyna  "  fir-tree,  lance, 
American  birch,  and  "  raspberry  wood,"  so  called  from  its 
strong  odor  resembling  strawberries.  A  specimen  of  wood, 
u  name  not  known,"  but  much  resembling  the  Zebra  variety, 
