[     393     ] 
XXXII.  A  New  Improved  Type  of  Chronograph.  By 
Robert  Ludwig  Mond,  21. A.,  F.R.S.E.,  and  Meyer 
Wilderman,  Ph.D.,  B.Sc* 
[Plate  VIII.] 
IX  the  course  o£  a  physico-chemical  investigation  we  made 
some  years  ago  a  chronograph  measuring  time  to  0*1 
second  was  required.  We  procured  one  of  the  best  make 
with  a  revolving  drum  of  60  cm.  circumference  making-  one 
revolution  per  minute,  and  subjected  it  to  a  careful  investi- 
gation. We  found  on  calibrating  it  with  a  clock  making 
electrical  contacts  automatically  every  minute,  that  not  only 
was  the  absolute  value  of  each  revolution  not  equal  to  a 
minute,  but  that  the  differences  in  time  between  two  contacts 
proved  to  be  very  irregular  and  greatly  different.  On 
further  comparing  four  curves  obtained  successively  one 
after  another  with  the  same  instrument,  the  clock  having 
been  wound  up  afresh  every  time,  we  found  that  the  form 
and  shape  of  the  succession  of  the  contacts  of  each  spiral  was 
not  always  the  same,  so  that  no  correction  table  could  be 
applied  in  connexion  with  the  above  instrument.  Since  it 
is  exceedingly  difficult  to  get  a  large  revolving  drum  to 
move  at  the  above  speed  with  great  regularity,  it  was  evident 
that  unless  a  simultaneous  calibration  of  the  curve  is  made  for 
every  second  or  two  seconds,  the  above  type  of  instrument 
cannot  be  used  even  for  moderately  accurate  measurements 
of  time. 
Since  no  fault  could  be  found  with  the  workmanship  of 
the  instrument,  it  wras  evident  that  the  reasons  for  these 
irregularities  had  to  be  looked  for  in  the  principle  upon 
which  the  instrument  for  high  speeds  was  constructed. 
This  it  was  not  difficult  to  discover.  It  is  a  well-known  fact 
that  very  little  is  required  to  stop  a  clock,  and  still  less  to 
make  its  movements  irregular.  By  making  a  clock  drive  a 
drum  with  a  speed  of  one  revolution  per  minute  instead  of 
21  hours,  the  clock  has  to  do  about  1000  to  1500  times  more 
work,  and  the  solution  of  the  problem  for  chronographs  of 
higher  speed  could  therefore  be  only  effected  if  this  enormous 
increase  of  work  of  the  clock  could  be  correspondingly 
counterbalanced  by  a  reduction  in  the  work  the  clock  has  to 
do  per  each  revolution. 
The  principles  upon  which  our  chronograph  was  worked 
out  can  be  summarized  as  follows  : — (1)  Instead  of  moving 
the  heavy  drum,  thick  screw,  and  the  one  or  two  carriages 
*  Communicated  by  the  Authors. 
Phil  Mag.  S.  6.  Vol.  11.  Xo.  63.  March  1906.  2  D 
