342 
Dr.  Gundry  on  the  Asymmetrical  Action  of  an 
Apparatus  and  Experiments. 
For  the  production  of  the  alternating  current,  I  used  partly 
the  sine-inductor  of  Kohlrausch  and  partly  the  Dolezalek 
alternating-current  machine,  made  by  Siemens  and  Halske. 
In  the  former,  the  rotation  of  a  magnet  in  the  form  of  a 
small  disk  inside  a  coil  gives  a  current  of  very  pure  sine 
form.  By  use  of  different  weights  to  drive  the  clockwork 
I  could  obtain  currents  of  frequency  80~  to  120-^  per  sec. 
With  the  Dolezalek  machine,  in  which  the  iron  circuit  of  an 
electromagnet  is  almost  completed  and  broken  120  times 
during  each  revolution  of  a  wheel  and  a  current  induced  in 
a  secondary  wound  round  the  magnet,  a  current  up  to 
5000~  per  sec.  (10,000  pole  changes)  could  be  obtained. 
For  the  measurements  of  alternating-current  strength  I 
used  an  electrodynamometer  of  the  Kohlrausch  type,  which 
gave  a  double  deflexion  of  1  mm.,  read  with  telescope  and 
scale  at  a  distance  of  1  metre,  for  a  current  0*72  X  10~4  amp. 
For  alternating  currents  too  small  to  measure  directly  I 
measured  the  E.M.F.  of  the  machine,  using  a  measurable 
current  and  known  resistances,  and  calculated  from  the 
resistances  in  use  at  any  time  the  current  strength. 
The  direct  currents  were  measured 
by  galvanometers  of  moving-coil  type. 
In  some  cases  a  direct-reading  galva- 
nometer   of    sensitiveness    1    div.    for 
Fi-.  1. 
was 
used, 
galvanometer 
and 
of 
m 
sen- 
1 
(double    throw)    fo] 
m  a  *\ 
contained 
layer   of   mercury, 
large 
5-5  X  10 ~7    amp. 
others  a  mirror 
sitiveness    1  mm 
1-32  xlO-9  amp. 
The    electrolyte  was 
small   beaker.      A 
covering  the  bottom,  formed  the  .. 
electrode.    The  electrical  connexion  with 
it  was  made  with  a  platinum  wire  sealed 
in  a  glass  tube  in  the  ordinary  way. 
Dipping  in  the  solution,  there  was  a 
capillary  tube  of  the  form  shown  in  fig.  1. 
The  small  limb,  about  3  cm.  long,  had 
an  inner  diameter  of  2 '14  mm.  The 
wider  limb  had  a  diam.  1^  cm.  The 
mercury  meniscus  was  from  2  to 
the  tube. 
In  some  experiments  the  E.M.F.  between  the  electrodes 
was  directly  measured  with  a  Dolezalek  quadrant  electro- 
meter.    Its  sensitiveness  was  1  mm.  for  0*0043  volt. 
mm//////MY////M////M 
cm.  from  the  open  end  of 
