Popham tells us that his _Telegraphic Signals, or Marine Vocabulary_ ("telegraphic" being, of course, used thirty years before the invention of the electric telegraph, in its primary sense of writing at a distance) was originally compiled in 1800, to facilitate the conveyance of messages from Popham's ship, the 'Romney,' off Copenhagen, to Admiral Dickson, off Elsinore, when that officer, with a squadron of ships, was giving additional weight to the British Ministers' arguments with the Danish Court. "Its utility was in that instance so obvious and so generally allowed by the Captains of the North Sea Squadron that Sir Home Popham conceived it might be brought into more extensive practice."
The first edition of this code consisted of nearly 1000 words chosen by Popham from the dictionary as most useful for naval purposes. In 1803 a second part, consisting of nearly 1000 less useful words, and a third part, consisting of nearly 1000 "sentences most applicable to military or general conversation" were added. To prevent the signal numbers from becoming unduly high, derivations were grouped with their root-word, e.g. expedite, expedited, expediting, expedition, and expeditious were each expressed by No. 270, it being left for the receiver to determine the exact word by the context. Further, "In verbs, the number, person, tense and mood" had to "be applied to the sense of the sentence." When the exact word was not in the vocabulary, the one most nearly synonymous was to be adopted, but "should it be of any consequence to use a word not in the vocabulary," it could be spelt by the numerical alphabet, which was known by the numbers 1 to 25. It may be noted, as the solution of the conundrum that has puzzled many in spelling out "duty" in Nelson's celebrated signal that in this alphabet, not only are I and J treated as one letter, but V precedes U.
Thus, in the preparation for that signal, when Pasco told Nelson that "confides" was not in the vocabulary, he suggested the "one nearest synonymous," namely, "expects," as this latter could be expressed by three flags in one hoist, while "confides" required 11 flags in eight hoists. "Duty," however, had to be spelt[389]. The sentiment of the signal had been sufficiently spoilt by the substitution of "expects" for "confides"; the further substitution of "best" or "utmost" would have hopelessly ruined it.