Timing

[RUSS, Brian]

One of the fascinations of dialling for me is the still-unexpected richness 
of the field, going beyond, as it does,  the simple matter of an alternative 
to a clock. On this latter point, a clock is used for telling the time but 
also for measuring elapsed time - as an egg-timer does. Does anyone know of 
a gnomonic method or device to measure short periods of time (say, four and 
a half minutes) separately from telling the time ?