400 
ME.  EAIEBAIEN  ON  THE  EESISTANCE  OE  TEEES  TO  COLLAPSE. 
The  next  experimented  upon  was  a steel  tube,  of  the  same  form  and  with  similar 
rigid  divisions  to  those  of  the  iron  one.  This  sustained  220  lbs.  on  the  square  inch, 
when  it  bulged  in  or  collapsed  in  the  middle  division. 
The  last  was  a plain  tube  of  similar  plates  of  iron,  14|-  inches  in  diameter,  but  with- 
out ribs.  This  collapsed  with  a pressure  of  125  lbs.  on  the  square  inch ; and  this  agrees 
nearly  with  the  preceding  experiments,  as  will  be  seen. 
Comparing  Experiments  32  and  33,  it  would  appear  that  the  steel  tube  is  not  stronger 
than  the  iron ; but  we  are  not  warranted  in  drawing  general  conclusions  from  a single 
experiment. 
The  next  experiments  were  of  a different  character,  upon  tubes  of  an  elliptical  form. 
The  following  Table  gives  the  results. 
Table  X.  Eesistance  of  Elliptical  Tubes. 
Mark. 
6 
liameter. 
inches. 
Length. 
inches. 
'hickness. 
inch. 
ressure  of 
collapse, 
lbs.  per 
uare  inch. 
Remarks. 
1— 1 
fc-< 
A 
Aa. 
o 
X 
60 
•043 
6*5 
1 
34 
'U 
- 
35 
20|xl6i 
61 
•250 
127-5 
^ I 
X. 
22 
18| 
61 
•250 
420-0 
Cylindrical. 
T. 
19 
12 
60 
•043 
12-5 
The  last  two  experiments  on  cylindrical  tubes  are  appended  for  comparison. 
On  comparing  the  elliptical  tube  B5  with  the  cylindiical  tube  X,  which  are  of  the 
same  length  and  thickness  of  plates,  and  only  about  half  a square  inch  different  in  sec- 
tional area,  we  have  for  the  collapsing  pressiue  of  the  former  127’5  lbs.,  and  for  that  of 
the  latter  420  lbs.,  where  it  will  be  observed  there  is  a loss  of  about  yths  of  the  strength, 
in  consequence  solely  of  the  flattening  of  the  tube  B5,  or  in  other  words,  a cylindiical 
tube  will  support  nearly  three  times  the  pressure  which  would  collapse  an  elliptical  tube 
of  the  same  weight  when  proportioned  like  tube  BJ.  A similar  deficiency  is  observable  ^ 
in  tube  Aa,  when  compared  with  tube  T.  The  change  of  form,  from  the  cylinder  to  1 
the  ellipse,  where  the  diameter  was  reduced  1^  inch  in  one  dii’ection  and  extended  as  ; 
much  in  another,  reduced  the  bearing  powers  one-half.  The  comparative  results  ; 
obtained  from  the  experiments  on  the  thick  tube  are  different  from  those  on  the  thin  I 
