Meanwhile, John McArthur, a purser in the navy, who had during the war of American Independence been frequently stationed to observe signals in the fleet and had therefore practical experience of the delays, difficulties and misunderstandings that occurred with the older methods of signalling by flags in particular positions, had been for many years at work on a new code which he submitted to the Admiralty in 1790. The basis of this plan was the old tabular system with two flags hoisted together or separately at the most conspicuous parts of the ship. The code contained upwards of 550 signals, with provision for an indefinite increase, and incorporated an ingenious device for continuously altering the numerical value of the flags. It was an advance upon any of the codes hitherto in use, but "some scruples of delicacy intervened in the adoption of any new plan of signals which would supersede that of Earl Howe's numerary code," and it was not adopted. Nevertheless, it attracted the attention of Hood, then the Senior Sea Lord, and on his appointment to command the Russian armament in 1791 he made McArthur his secretary. McArthur then turned his attention to re-arranging Howe's signals "by simplifying the form with Indices for facilitating their being made and understood, and engrafting in the body and instructions many new ideas and instructions of his own." Howe approved of the alterations, and the revised code was then printed and issued to Hood's fleet. This "new arrangement" was introduced by Hood in 1793 into the Mediterranean and continued to be used there until 1799. It was the signal book in use at the Battles of St Vincent and the Nile. In it the values of Howe's numeral flags, as shown in Col. 1 of [Plate XIII], were transposed as follows: 1 became 4; 2, 9; 3, 7; 4, 2; 5, 6; 6, 0; 7, 8; 8, 5; 9, 3; and 0, 1. The tabular flags were also transposed, 1 becoming 8; 2, 7; 3, 5; 5, 3; 6, 2; 7, 1; 8, 6; while 4 remained of the same value.
[(iv) THE VOCABULARY SIGNAL BOOK]
With the compilation, in 1790, of Howe's second signal book, we have the end of that system, or want of system, which is especially noticeable during the American War of Independence, under which the signals used in each fleet or squadron varied with the idiosyncrasies of each individual commander-in-chief. Henceforth, although it was usual for the admiral commanding each fleet to add a few of his own devising, the bulk of the signals were, so to speak, stereotyped in form, and were in general use throughout the British navy.
In 1799 the Signal Book for the Ships of War was increased in size to 167 pages by the addition of an index to the signals and the inclusion of the printed instructions. The "Private ship" signals were placed at the end of the "Admiral's signals" and numbered consecutively after them, so that the "tabular" flags disappear, and all signals are henceforth made by the simple numerary code, the total number being increased from about 260 to 340.
It will be seen from the plate of numeral flags that Howe's numerals were continued in the 1799 book with only two slight modifications: No. 1, instead of being a plain red flag, became yellow, red, yellow, in three equal horizontal stripes, and the substitute became plain white. But his arrangement was simplified. The half black and white flags were done away with as unnecessary, since their meanings could equally well be expressed by those remaining.
In addition to the signal book, each commander-in-chief compiled for his own fleet a tabular "pendant board," on which two pendants were assigned to the name of each ship of his fleet. By this means he was enabled to address any of the signals to a particular ship, without making the command general to the whole squadron. For example, Nelson, at Trafalgar, before making general his favourite signal, "Engage the enemy more closely," addressed it particularly to the 'Africa,' which, having become separated over night, found herself at a distance from the two columns, and, just before the commencement of the action, was sailing near to the enemy's van, on an opposite and parallel course. This he did by hoisting flags Nos. 1 and 6, together with the pendants appropriated to the 'Africa's' name on the "pendant board."
But a code for signalling or other purposes is like a language; if the language is what we call "dead," i.e. if words have ceased to be added to it, it is of little use for expressing every-day needs. Similarly, if the navy is not stagnating, continual amplification of tactics or of every-day details necessitates an increase in the range of conversation between the Admiral and his fleet. Although at the time of the battle of Trafalgar the signal book was only six years old, it had already had its range of signals increased by upwards of 80 additions, made in manuscript, on such varied matters as:
412. "The ships or vessels chased have separated on different courses."
280. "Send for fresh beef immediately."
291. "Engage the enemy as close as possible."