Flags are nowadays ordinarily made of bunting, a woollen fabric which, from the nature of its texture and its great toughness and durability, is particularly fitted to stand wear and tear. It comes from the Yorkshire mills in pieces of forty yards in length, while the width varies from four to thirty-six inches. Flags are {23} only printed when of small size, and when a sufficient number will be required to justify the expense of cutting the blocks. Silk is also used, but only for special purposes. Flag-devising is really a branch of heraldry, and should be in accordance with its laws, both in the forms and the colours introduced. Yellow in blazonry is the equivalent of gold, and white of silver, and it is one of the requirements of heraldry that colour should not be placed upon colour, nor metal on metal. Hence the red and blue in the French tricolour (Fig. 191) are separated by white; the black and red of Belgium (Fig. 236) by yellow. Such unfortunate combinations as the yellow, blue, red, of Venezuela (Fig. 170); the yellow, red, green of Bolivia (Fig. 171); the red and blue of Hayti (Fig. 178); the white and yellow of Guatemala (Fig. 162), are violations of the rule in countries far removed from the influence of heraldic law. This latter instance is a peculiarly interesting one; it is the flag of Guatemala in 1851, while in 1858 this was changed to that represented in Fig. 163. In the first case the red and the blue are in contact, and the white and the yellow; while in the second the same colours are introduced, but with due regard to heraldic law, and certainly with far more pleasing effect. One sees the same obedience to this rule in the special flags used for signalling, where great clearness of definition at considerable distances is an essential. Such combinations as blue and black, red and blue, yellow and white, carry their own condemnation with them, as anyone may test by actual experiment; stripes of red and blue, for instance, at a little distance blending into purple, while white and yellow are too much alike in strength, and when the yellow has become a little faded and the white a little dingy they appear almost identical. We have this latter combination in Fig. 198, the flag of the now vanished Papal States. It is a very uncommon juxtaposition, and only occurs in this case from a special religious symbolism into which we need not here enter. The alternate red and green stripes in Fig. 63 are another violation of the rule, and have a very confusing effect.[14]