In  Moison*s  integrating  dynamometer  a  ratchet-wheel  is  driven
by  the  strokes  of  a  click.  (See  Articles  194  to  196,  pages  206  to
211.)    The  number  of  these  strokes  in  a  given  time  is  proportional

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DYNAMOMETERS — MSASUBEMENT  OP  FRICTION.  3D5

to  the  speed  of  the  machine  whose  work  is  to  be  measured ;  and  hy
means  of  a  dynamometer-spring  the  length  of  each  stroke  of  the
click  is  adjusted  so  as  to  be  proportional  to  the  effort  exerted  at
the  time.  The  result  is  that  the  total  extent  of  motion  of  the
ratchet-wheel  in  a  given  time  is  proportional  to  the  work  performed.
It  is  obvious  that  the  frictional  catch  might  be  implied  to  this
apparatus  (Article  197,  page  211).
348.  Mmmwmmm  •r.VHdiMi. — Under  the  head  of  Dynamo-
meters may  be  classed  apparatus  for  the  experimental  measurement
of  friction.
If  by  means  of  any  kind  of  dynamometer  whose  use  does  not
involve  the  interruption  of  the  p^ormance  of  the  ordinary  work
of  a  train  of  mechanism,  we  measure  the  power  transmitted  at  two
parts  of  that  train,  the  difference  will  be  the  power  expended  in
overcoming  the  friction  of  the  intermediate  parts.  Him's  Pan-
dynamometer  (Article  344,  page  387)  seems  well  adapted  for  ex-
periments of  this  class.  The  power  of  a  steam  engine,  as  exerted
in  the  cylinder,  may  be  measured  by  means  of  the  indicator,  and
the  power  transmitted  to  machinery  which  that  engine  drives,  by
a  suitable  dynamometer;  and  the  difference  will  be  power  ex-
pended chiefly  in  overcoming  the  friction  of  the  inteimeiiate
mechanism.
