New  Improved  Type  of  Chronograph.  397 
in  all  its  parts;  its  movement  is,  owing  to  inertia,  for  this 
reason  not  of  a  uniform  character,  and  this  upsets  the 
regularity  of  the  movement  of  the  clock.  In  our  instrument 
the  parts  /  and  /'  themselves  form  the  axis,  and  the  two 
cross-pieces  (h  and  h')  with  the  nut  (v)  form  the  arms  of  a 
balance  carrying  the  weights  to  be  adjusted  to  each  other  by 
means  of  the  screw  and  nut.  It  is  of  no  little  importance 
for  the  accuracy  of  the  spiral  obtained,  that  in  our  instrument 
this  result  is  prod  need  by  one  moving  part  only,  while  in 
other  instruments  it  is  produced  by  several  moving  parts, 
which  in  the  nature  of  things  can  never  be  made  to  be 
absolutely  dependent  one  upon  another. 
We  now  pass  to  the  description  of  our  improved  means  for 
operating  and  working  the  writing-pen.  After  many  trials 
and  modifications  the  following  arrangement  was  adopted. 
A  bell-crank  is  provided  at  the  end  of  the  cross  arm,  one  of 
its  arms  being  connected  by  a  rigid  link  to  the  armature  (A) 
of  the  magnet,  while  the  other  is  connected  in  a  similar 
manner  through  the  axial  hole  in  the  pen-arm  to  the  penholder 
itself.  The  end  of  the  pen-arm  carries  a  small  cross-head 
from  which  two  guides  (g  and  g')  parallel  to  the  arm 
project.  A  cross-piece  to  the  centre  of  which  the  operating 
link  is  connected  slides  on  these  guides,  its  motion  being 
controlled  by  light  flexible  springs  (s  and  s!)y  and  to  the 
cross-piece  a  flexible  strip  carrying  the  pen  is  secured.  The 
pressure  with  which  the  pen  bears  upon  the  drum  is  regulated 
by  a  small  screw  (a)  acting  between  the  flexible  strip 
and  the  cross-piece.  In  our  newest  type  of  chronograph 
arrangements  are  made  to  raise  the  pen  from  the  drum,  when 
the  paper  is  changed,  so  that  the  pressure  of  the  pen  upon 
the  drum,  once  adjusted,  should  always  remain  absolutely 
the  same.  For  this  purpose  a  little  plate  carrying  the 
writing-pen  with  the  screw  is  hinged  to  the  cross-piece.  This 
arrangement  provides  a  very  steady  support  for  the  pen, 
making  vibrations  of  the  penholder  impossible  and  keeping 
the  pen  in  all  positions  of  the  spindle  at  exactly  the  same 
distance  from  the  drum  (instead  of  resting  on  it),  and  this 
enables  the  pen  to  be  brought  just  so  near  to  the  drum  as  is 
necessary  to  trace  a  spiral  on  the  same,  i.  e.  with  the  least 
possible  friction.  To  the  arm  carrying  the  pen  a  reservoir 
containing  a  considerable  quantity  of  ink  may  be  fixed,  from 
which  the  ink  flows  into  the  pen  through  a  capillary  tube,  or 
a  capillary  tube  containing  a  cotton  thread.  By  this  means 
the  pen  never  becomes  dry,  and  there  is  no  necessity  tor 
repeated  cleaning  and  filling  with  ink. 
The    writing- pen    is    actuated    electrically.     The    current 
