[time-nuts] Clock Calibration

[Perry Sandeen]

List,

I was reading some of the history of mechanical clocks and was astonished to see that one guaranteed its accuracy to 2 milliseconds per day! (And it was) Now this same clock when tested with modern equipment tested to be accurate to 200 micro-seconds per day.  Astonishing!

This got to wondering how the heck they were able to calibrate a clock to milliseconds per day back then?

And as extension to that question, how do they prove the accuracy of F1 or other similar time standards?

Regards,

Perrier