ME.  EAIEBAIEN  ON  THE  EESISTANCE  OF  TTJBES  TO  COLLAPSE. 
393 
On  consulting  the  above  Table,  it  appears  that  tubes  of  the  same  diameter  and  the 
same  thickness  of  plates  vary  in  strength  when  of  different  lengths.  The  tubes  of 
19  inches  and  those  of  40  inches  differ  widely  in  their  powers  of  resistance.  Comparing 
the  results  of  Experiments  1 and  2 with  those  of  Experiments  3 and  4,  we  find  that  the 
latter,  while  of  twice  the  length,  bear  less  than  half  the  pressm’e.  Comparing  these 
with  Experiment  5,  we  find  that  tube  E,  5 feet  long  or  three  times  as  long  as  A and  B, 
exhibits  only  about  one-third  of  their  mean  strength.  Similarly,  E,  which  is  f the  length 
of  D,  bears  only  about  f the  pressure. 
Tube  F,  Experiment  6,  may  be  considered  as  composed  of  three  distinct  tubes,  each 
1 foot  7 inches  long.  It  was  made  with  two  perfectly  rigid  rings,  soldered  to  the  outside 
of  the  tube  to  keep  it  in  form  and  prevent  collapse  at  those  points.  The  result  of  this 
alteration  was  to  increase  the  strength  of  the  tube  threefold,  as  is  evident  on  comparing 
it  with  tube  E. 
Table  II.  Resistance  of  6-mch  Tubes. 
This  Table  gives  indications  of  the  same  law  of  resistance  as  the  last.  It  will  be 
* On  removing  the  tubes  G,  H,  it  was  found,  that  owing  to  the  thinness  of  the  metal,  the  cast-iron  ends 
of  both  had  been  fractured,  causing  collapse,  perhaps,  before  the  outer  shell  had  attained  its  maximum 
resistance. 
t Tube  M had  an  iron  rod  down  its  axis  to  prevent  the  ends  approaching  each  other  during  collapse ; a tin 
rmg  had  also  been  left  in  by  mistake,  which  accounts  for  the  increased  pressure  required  to  produce  collapse. 
3 G 2 
