To "Engage the enemy"; the same flag at the fore top masthead, just as in 1653. "To come to a closer engagement"; the blue and white flag (two horizontal stripes) at the fore topgallant masthead under the signal for engaging. In this code we reach the culmination of the old system of signalling by means of a large number of different flags each having a different meaning according to the position in which it was shown. (iii) THE INVENTION OF NUMERARY SIGNALS The development of tactics and fleet organisation and the consequent increase of the signals had been so rapid during the latter half of the eighteenth century that the old methods had become inadequate. In 1746 there were 16 flags in use to express 144 signals, by 1780 there were about 50 flags, each hoisted on an average in seven different positions, providing for about 330 signals. Twenty-five years later the Trafalgar signal book contained upwards of 400, not including those in Popham's Code. So long as the signals were few in number, so that the flags could be made in a few strongly contrasted designs, and only the most prominent positions need be used for them, the old system had the advantage of simplicity, but when the signals multiplied, less conspicuous positions and less strikingly differentiated flags had also to be made use of, and simplicity gave place to complexity. It must be remembered that flags at sea have to be distinguished not only when a fair breeze is unfurling them plainly to the view; they have also to be distinguished in a dead calm when they hang down along the halyards, and when distance and haze lend enchantment to the view but not to the signalman. In order that the differences in the flags may be readily distinguishable at sea in any circumstances two conditions are essential-- (1) The colours must be quite unlike, so that they do not "merge" at a distance. (2) The designs of the flags must be simple and not complicated. In practice this limits the colours to the following: Red, blue, and yellow, with black and white. Moreover, it is found that when two of these colours are to be shown in one flag they should be of one of the following combinations: red and white, yellow and blue, blue and white, or black and white. But with so many as 40 flags it was impossible to adhere to these two rules.