16 
PHARMACEUTICAL  GLEANINGS. 
the  Pharmaceutical  Journal,  and  represents  a  machine  originally 
described  in  Armingand's  Grenie  Industrie^  November,  1852, 
Fig.  17. 
page  233.  "  It  is  very  simple,  easily  managed,  and  has  the 
greater  advantage  of  being  applicable  to  any  kind  of  balance,  as 
-well  as  admitting  of  the  true  weight  of  the  substance  weighed 
being  placed  alone  on  the  balance,  thus  obviating  any  chance  of 
error  from  calculation." 
The  arrangement  consists  of  a  brass  tube  A,  A,  in  which  slides 
a  steel  rod  B,  loaded  at  the  ends  with  the  knobs  D.  The  knob 
D'  attached  to  the  other  end  of  the  tube  acts  as  a  counter  poise 
to  D.  The  tube  is  attached  at  either  end  of  the  beam  by  the 
arms  hi.  A  small  spring  is  placed  in  the  interior  of  the  tube, 
which,  by  pressing  on  the  steel  rod,  B,  prevents  it  from  moving 
unless  pulled  by  the  operator.  , 
When  the  rod  is  pushed  into  the  tube  till  the  knob  D  touches 
it,  the  balance  is  in  equilibrium.  When  the  operator  is  desirous 
of  taring  a  vessel  he  places  it,  as  V,  on  the  pan  P',  and  gradually 
draws  out  the  rod  B,  until  the  knob  counterpoises  the  vessel.  It 
follows  of  course  that  the  object  to  be  tared  must  always  be  put 
on  the  pan  opposite  the  knob  D ;  although  not  suggested  by  the 
inventor,  we  do  not  see  why  the  rod  B  may  not  be  graduated  to 
indicate  the  weight  correctly,  even  to  the  fractions  of  an  ounce, 
and  thus  very  materially  add  to  the  usefulness  of  the  contrivance, 
