4
Light measurements
4.1 Units, terminology and calculations
To measure and record light a unit was required that could be understood and repeated experimentally. This was the candle – but not any old candle. It had to be well defined so that it was repeatable (well, almost repeatable). It is quite laughable today to think of a world wide standard measurement of light being dependent on the repeatability of a burning candle, but it is a fact and the specification for the standard candle defined the type of wick and the tallow mixture to be used and the dimensions were an 
inch wick and a candle with a diameter of 1 inches.
Owing to the unreliability ...
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