Wiktionary
patent log
n. (context nautical English) A taffrail log
WordNet
patent log
n. a torpedo-shaped log with rotary fins that measure the ship's speed [syn: screw log, taffrail log]
Usage examples of "patent log".
Wolf Larsen was smoking a cigar and examining the patent log which the Ghost usually towed astern, but which had been hauled in for some purpose.
The new steamer shot along wonderfully, and the patent log showed a speed of seventeen miles an hour, a speed which as yet no English, French, or American boat had ever obtained.
The patent log on the taffrail periodically rang a single tinkling stroke for every mile traversed on an errand of faith.