[PRCo] Non-Traction Question for Those Who Know

[Ken & Tracie]

First off, the attached image was taken in Milwaukee, not Western 
Pennsylvania.
Secondly, this is a non-traction question, but I suspect some of the old 
timers and engineering experts can give me an answer to a life long 
question.

How did these collapsible gas (not gasoline) tanks work?  What kept them 
from leaking as they lowered or were filled?

Also, could they hold any sort of gas, i.e., natural gas, propane, coke 
generated gas, etc.?

Thanks in advance for your replies.

K.


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