In the early days of computers they used to use a length of wire as
temporary memory. At the start of a store cycle a piece of data would be
input to the wire, after a period of time the data would come out and be
placed into the computation.
Admiral Grace Hopper used to give an example of time and delay in her
speeches. She would say that one day she called down to the computer
department and asked for a micro second. They sent her 1000 feet of
wire. She then called down and asked for a nanosecond, they sent her one
foot of wire. No point to this just a good story.

Dave N
The delay lines I encountered at IBM that were used for storage were
"sonic" delay lines. They were driven in a torsion mode (mechanical)
and were very reliable up to about 10 milliseconds(I think!) of data.
Above that they began to be temperamental and required constant
temperature ovens. The larger ones were used as video storage with a
screen of data in each instance.

Delay lines running at light speed (about a NS per ft) were used as
clock generators by inputting a pulse and tapping the line down stream
for a very stable clock sequence.

John Ferrell W8CCW