398 
ME.  FAIEBAIEN  ON  THE  EESISTANCE  OE  TEEES  TO  COLLAPSE. 
Table  VII.  Resistance  of  8-incli  Tubes. 
Mark. 
No. 
Dia- 
meter. 
inches. 
Length. 
inches. 
Thickness. 
Pressure  of 
collapse, 
lbs.  per  sq.  in. 
Remarks. 
AA. 
25 
8 
60 
•043 
22 
BB. 
26 
8 
30 
•043 
36 
% 
In  the  above  experiments  the  tubes  do  not  appear  to  follow  precisely  the  law  of 
“ inversely  as  the  length.”  Had  they  done  so,  the  tube  BB  should  not  have  yielded 
with  a less  pressure  than  44  lbs.  on  the  square  inch.  It  is,  however,  impossible  to  manu- 
facture these  tubes  truly  cylindrical,  and  hence  it  follows  that  shght  variations  may  very 
materially  affect  the  ultimate  strength  of  the  tube. 
From  three  experiments  on  4-inch  tubes,  we  derive  data  more  in  accordance  with  the 
law,  as  will  be  seen  below. 
Table  VIII.  Resistance  of  4-inch  Tubes. 
Mark. 
No. 
Diameter. 
inches. 
Length. 
inches. 
Thickness. 
inch. 
Pressure  of 
collapse, 
lbs.  per  sq.  in. 
cc. 
27 
4 
60 
•043 
47 
DD. 
28 
4 
30 
•043 
(195) 
EE. 
29 
4 
30 
•043 
93 
FF. 
30 
4 
15 
•043 
147 
Remarks. 
In  the  above  experiments,  the  second  on  tube  DD  is  lost,  in  consequence  of  the  endsj 
being  fractured  and  the  water  obtaining  admission,  so  as  to  cause  a counteracting 
pressure  in  the  interior.  Experiment  29  agrees  closely  with  the  law  when  compai'ed 
with  27,  its  strength  being  correctly  double  that  of  the  latter.  The  15-inch,  although 
not  four  times  the  strength  of  the  60-inch,  exhibits  high  resisting  powers.  It  is  pro 
bably  difficult  to  reconcile  these  discrepancies ; but  we  have  in  these  experiments  suffi 
cient  data  to  show  that  these  tubes  also  follow,  in  their  resistance  to  collapse,  souk 
