ME.  EAIEBAIEN  ON  THE  EESISTANCE  OF  TUBES  TO  COLLAPSE. 
391 
Fig.  1. — Yertieal  section. 
pressure  was  required,  it  was  deemed  advisable  to  let  it  escape  by  the  cock  e,  and  to 
effect  rupture  through  the  medium  of  water  only.  In  both  these  cases  a perfectly 
uniform  pressure  was  ensured  upon  every  part  of  the  tube  to  be  collapsed. 
These  preparations  having  been  made,  and  the  pressure-gauges  carefully  adjusted,  the 
experiments  proceeded  as  shown  in  the  following  Tables. 
The  first  experiment  was  upon  a tube  4 inches  in  diameter,  and  1 foot  7 inches  long 
between  the  cast-iron  ends,  to  which  it  was  riveted  securely  and  brazed.  It  was  composed, 
as  in  the  other  experiments,  of  a single  thin  plate,  bent  to  the  required  form  upon  a man- 
diil,  and  riveted  and  also  brazed  to  prevent  leakage  into  the  interior.  This  tube  having 
been  fixed  to  the  cylinder  covers  in  the  manner  described  above,  the  pump  was  applied 
and  a gradually-increasing  force  given  to  its  exterior  surface,  until  its  powers  of  resist- 
ance were  overcome.  During  the  experiments  the  precaution  of  allowing  the  air  to  escape 
at  high  pressures  was  found  absolutely  necessary,  as  the  tubes  generally  collapsed  with  an 
explosion  of  the  suddenly-compressed  air  in  the  tube  D,  fig.  I,  accompanied  by  a loud 
report  as  it  made  its  escape  by  the  pipe  m.  These  explosions  give  pretty  correct  indica- 
tions of  what  takes  place  when  the  internal  flues  of  boilers  collapse. 
It  has  long  been  a desideratum  to  determine  some  law  by  which  the  engineer  could 
calculate  the  proportionate  strength  of  the  internal  flues.  Hitherto  we  have  acted  upon 
the  principle  that  the  cylindi’ical  flues,  as  ordinarily  constructed,  were  considerably 
MDCCCLVIII.  3 G 
