Light Units
The British Unit is the light of a spermaceti candle 7/8-inch in diameter, burning 120 grains per hour (six candles to the pound). They sometimes vary as much as 10 per cent, from the standard. Mr. Vernon Harcourt’s standard flame is equal to an average standard candle.
The French Unit is the light of a Carcel lamp, and is equivalent to 9 T/Z British units.