628 
Report  on  Implements  at  York. 
Steam-boilers  (Fawcett  and  Hargreave’s  Patent).  The  valve 
itself  is  an  ordinary  dead-weight  safety  valve,  but  is  attached  to 
a lever  inside  the  boiler,  with  floats  at  either  end,  which  cause 
the  valve  to  lift  when  the  water  is  either  at  too  high  or  too  low 
a level.  The  valve  is  contained  in  a lock-up  box,  and  the 
liberated  steam,  instead  of  escaping  into  the  air,  finds  its  way 
by  a pipe  to  the  crown  of  the  flue,  discharging  its  steam  over 
the  hottest  part  of  the  fire,  and  thus  at  once  damping  down  the 
fire.  If  the  escape  is  due  to  too  high  pressure,  the  damping 
down  of  the  fire  at  once  has  the  desired  effect  of  lowering  the 
pressure  of  the  steam  ; fuel  is  economised,  and  directly  the  steam 
discharge  ceases,  the  fire  brightens  up  again.  If  it  occurs  from 
either  the  water  being  too  low  or  too  high,  the  engine-driver’s 
attention  is  directed  to  the  fact,  and  he  regulates  the  pnmps 
accordingly.  The  drawings  and  details  on  p.  627  will  fully 
explain  this  very  ingenious  invention. 
It  will  be  gathered  from  above  that  the  safety  valve  of  Messrs. 
Fawcett  and  Hargreaves  not  only  provides  for  the  escape  of 
steam  which  otherwise  might  become  dangerous,  but  utilises  the 
steam  to  correct  the  cause  of  excessive  pressure,  and  thus 
prevents  useless  consumption  of  fuel,  and  at  the  same  time  the 
noise  of  the  escaping  steam  calls  the  attention  of  the  engineer  to 
the  reason  for  the  escape.  If  by  any  carelessness  the  driver  was 
absent  and  the  water  had  become  too  low,  and  might,  if  unchecked, 
result  in  an  accident,  it  is  quite  evident  that  long  before  any 
of  the  heating  surfaces  could  be  uncovered  the  fire  would  be 
extinguished ; and  therefore,  so  long  as  the  apparatus  is  in 
working  order,  its  action  is  perfect.  The  danger  of  automatic 
appliances  is  that  they  tend  to  make  the  attendants  careless,  and, 
being  entirely  depended  on,  if  through  any  cause  they  fail  to 
act,  accidents  may  occur.  It  is  not,  however,  easy  to  see  how 
such  simple  mechanism  could  get  disarranged,  and  we  think,  for 
fixed  boilers  especially,  the  arrangement  is  excellent.  The  price 
for  a single  flue  boiler  is  10Z.,  for  a double  flue  boiler,  12Z. 
fV.  Liplitfoot,  of  Stockton-on-Tees,  exhibited  an  Improved 
Potato  Riddler,  which  has  this  advantage  over  circular  revolving 
screens  like  that  of  the  East  Yorkshire  Wagon  Co.,  exhibited 
at  Reading,  and  figured  and  described  in  the  * Journal  ’ of  last 
year,  that  diseased  potatoes  can  be  hand-picked  off  the  screen. 
By  means  of  two  screens  we  get  a triple  division,  viz.,  best,  seed, 
and  small.  The  arrangement  will  be  gathered  from  the  drawing, 
which  gives  an  excellent  miniature  of  the  machine  (Fig.  28). 
The  two  screens  work  backwards  and  forwards,  or  rather  to  and 
fro  across  the  frame,  running  in  a groove  on  friction  wheels ; 
the  requisite  shaking  motion  is  thus  obtained  with  much  less 
fatigue  than  when  the  operator  holds  the  screen  or  sieve,  and  has 
