392 
ME.  FA  TEE  A TEN  ON  THE  EESISTANCE  OE  THBES  TO  COLLAPSE. 
stronger  than  the  outer  shell ; but  this  opinion  has  in  reality  no  foundation  in  experi- 
ment, excepting  only  uncertain  deductions  from  occasional  explosions  and  the  failure  of 
vessels  under  high  pressures  in  circumstances  of  a very  variable  and  doubtful  character. 
There  have  been  no  definite  rules  to  guide  us  hitherto  in  proportioning  the  diameter, 
length,  and  thickness  of  plates  of  the  fines,  so  as  to  correspond  with  the  strength  of  the 
boiler ; and  even  in  cases  where  explosions  have  taken  place  fi’om  collapse,  we  have,  it 
is  to  be  feared,  too  frequently  mistaken  the  actual  cause,  in  consequence  of  the  debris 
covering  the  site,  and  the  force  which  has  torn  to  pieces  the  outer  shell.  The  anoma- 
lous position  in  which  these  constructions  are  placed  has  greatly  retarded  the  applica- 
tion of  science  to  their  improvement,  and  there  appears,  in  fact,  to  be  no  rule  known 
by  which  to  attain  uniformity  of  strength  between  those  parts  of  a boiler  exposed  to  an 
internal  tensile,  and  those  exposed  to  an  external  compressive  force. 
To  supply  this  want,  and  to  remedy  certain  anomalous  results  arising  from  defective 
forms  of  construction,  it  appeared  desirable  that  these  vessels  should  be  subjected  to 
direct  experiment,  and  the  Laws  of  Eesistance  as  far  as  possible  ascertained,  and  the 
necessary  formula  deduced  for  the  future  guidance  of  the  practical  mechanic  and 
engineer.  These  objects  have,  it  is  believed,  been  attained  by  the  results  developed  in 
the  experiments  enumerated  in  the  following  Tables. 
EXPEEIMENTS. 
Resistance  of  Tubes  to  Collapse. 
In  these  experiments  the  tubes  were  composed  of  plates  of  uniform  thickness,  and  of 
the  form  and  size  shown  by  the  figures  in  the  column  of  remarks.  The  form  after  col- 
lapse is  also  indicated  by  the  woodcuts. 
Table  I.  Resistance  of  4-inch  Tubes. 
Mark. 
No. 
Diameter. 
inches. 
Length. 
inches. 
Thickness 
of  plates, 
inch. 
Pressure  of 
collapse, 
lbs.  per  sq.  in. 
A. 
1 
4 
19 
•043 
170 
B. 
2 
4 
19 
•043 
137 
C. 
3 
4 
40 
•043 
65 
D. 
4 
4 
38 
•043 
65 
E. 
5 
4 
60 
•043 
43 
F. 
6 
4 
60 
•043 
140 
Remarks. 
N.B.  The  figures  are  dra'wn  to 
a scale  of  in.  = 1 ft.  The  cross- 
sections  are  taken  through  the 
line  a b,  where  the  collapse  was 
greatest.  The  dotted  lines  show 
their  form  before  they  were  sub- 
jected to  experiment. 
I 
I 
