32  New  Micrometric  Govt  wmeter  Eye- Piece.  { 
Am.  Jock.  Pharm.. 
1872. 
well ;  for  the  fusion-point  is  very  high,  and  oxidation  occurs  only  at 
elevated  temperatures.  For  fine  balance-beams  and  weights,  lens- 
mountings,  reflectors,  laboratory  microscopes,  Sykes'  hydrometers^ 
still-worms,  egg-beaters,  camera  fittings,  and  a  variety  of  apparatus 
used  by  the  chemist  and  photographer,  the  nickel  coating  will  proba- 
bly find  extensive  application.  Oval  picture-frames  of  very  pretty 
effect  are  made  of  stamped  brass  coated  with  nickel.  Burnished  and 
matt  surfaces  of  this  metal  may  be  used  in  combination  for  ornamental 
purposes. — Technologist,  Dec,  1871,  from  the  Scientific  American. 
ON   A    NEW    MICRO  METRIC    GONIOMETER    EYE  PIECE  FOR 
THE  MICROSCOPE. 
By  J.  P.  Southwortu. 
After  a  few  experiments  by  Dr.  II.  T.  Porter  and  myself,  we  have 
succeeded  in  making  an  eye-piece  micrometer  and  goniometer  which 
equal  in  accuracy  and  surpass  in  simplicity  and  cheapness  any  we 
have  seen,  and  we  have  used  those  of  some  of  the  best  makers  in  this 
country.  The  objection  to  the  eye-piece  micrometers  in  use  is  the 
want  of  boldness  in  the  division-lines,  which  makes  them  fatiguing 
and  hurtful  to  the  eyes.  To  overcome  this  objection  we  were  led  to 
experiments  in  making  micrometers  by  the  aid  of  photography,  which 
have  resulted  in  success.    The  steps  of  the  process  are  these : — 
1st.  A  scale  of  100  heavy  India  ink  linesf  about  I  of  an  inch  apart, 
are  drawn  on  a  dead  white  surface  of  Bristol  board.  The  lines  marking, 
every  ten  divisions  are  six  inches  long  and  extend  one  inch  each  side 
of  the  scale  ;  those  marking  every  five  divisions  are  five  inches  long 
and  extend  one  half  inch  beyond  the  scale  ;  the  remaining  lines  are 
four  inches  long. 
2.  By  photographic  process  for  copying  engravings,  a  negative  m 
taken,  on  which  the  scale  equals  about  two  inches  in  length,  and  is, 
intensified  by  mercuric  chloride  and  potassium  cyanide. 
3d.  With  a  copying  camera  and  lens  for  taking  transparent  positives, 
for  the  magic  lantern,  a  transparent  positive  of  this  negative  is  taken 
on  micrometer  glass,  reducing  the  scale  to  the  length  of  one-half  inch. 
In  this  the  lines  are  -^-Ju  of  an  iRCn  apart.  After  intensifying,  wash- 
ing and  drying,  a  cover  of  thin  glass  is  cemented  on  with  Canada 
balsam,  and  the  slide  cut  to  fit  the  slit  in  the  micrometer  eye-piece 
