HINTS  TO  DISPENSERS.  347 
power,  not  only  of  giving  sparks,  but  even  of  attraction  upon 
the  lightest  bodies  !  This  applies  also  to  oak,  "pencil  cedar," 
horse  chestnut,  "Amboyna,"  black  thorn,  sycamore,  and  per- 
haps lime ;  while  the  rest  retained  their  power  very  well,  as 
sweet  chestnut,  acacia,  fir,  white  deal,  lignum  vitse,  &c,  &c. 
Most  woods  appear  to  keep  their  form  pretty  well  this  size,  and  to 
be  but  little  affected  by  the  heat  as  regards  "  warping,"  with  but 
two  or  three  exceptions,  as  boxwood,  lignum,  &c,  and  one  or  two 
others.  As  for  "  hornbeam,"  it  was  literally  doubled  up.  When 
I  stated  that  wood  presented  more  powerful  appearances  than 
ebonite  under  similar  circumstances,  I  referred  simply  to  the 
phenomenon  presented  by  the  former  when  two  eighteen  inch 
discs  were  laid  one  upon  another,  and  then  rubbed  gently  with 
catskin,  hareskin  or  rabbitskin  a  dozen  times  or  so ;  if  the 
uppermost  plat3  be  now  raised,  and  the  knuckle  presented,  the 
discharge  takes  place  in  a  single  spark  of  great  length  and  high 
intensity,  while  with  the  ebonite  circulars  the  sparks  appear 
much  shorter,  though  in  larger  quantity. 
In  conclusion,  I  may  remark  I  have  always  observed  that  the 
hardest  and  driest  woods — showing  no  visible  trace  of  moisture — 
invariably  take  the  longest  time  and  strongest  heat;  and  this 
circumstance,  in  connection  with  the  fact  that  I  have  very  fre- 
quently obtained  very  unequivocal  sparks  from  such  a  wood  as 
pine  while  still  strongly  steaming  before  the  fire,  would  seem  to 
warrant  the  supposition  that  this  curious  conversion  of  wood, 
by  long-continued  heat,  into  an  electric  might  depend  upon 
something  more  than  the  mere  and  simple  abstraction  of  water. 
\    I  am,  &c, 
F.  E.  S.  Jerningham. 
52  Cambridge  Terrace,  Hyde  Park,  April  27,  1866. 
— Loud.  Chem.  News,  May  11,  1866. 
HINTS  TO  DISPENSERS. 
By  Samuel  Taylor. 
The  subject  naturally  divides  itself  into  two  parts,  viz. : 
Hints  to  the  Head,  including  all  those  qualifications  of  mind 
and  temperament  which  fit  a  man  for  becoming  a  good  dis- 
