From infancy till the body has done growing, the contents both of the body and the face, and every part of their surface, are daily changing into more variety, till they obtain a certain medium (see page 78 on proportion) from which medium, as fig. [113 B p. II], if we return back to infancy, we shall see the variety decreasing, till by degrees that simplicity in the form, which gave variety its due limits, deviates into sameness; so that all the parts of the face may be circumscribed in several circles, as fig. [116 L p. II]. [Illustration: Figs. 113 and 116] But there is another very extraordinary circumstance, (perhaps never taken notice of before in this light) which nature hath given us to distinguish one age from another by; which is, that tho' every feature grows larger and longer, till the whole person has done growing, the sight of the eye still keeps its original size; I mean the pupil, with its iris or ring; for the diameter of this circle continues still the same, and so becomes a fixt measure by which we, as it were, insensibly compare the daily perceiv'd growings of the other parts of the face, and thereby determine a young person's age. You may sometimes find this part of the eye in a new-born infant, full as large as in a man of six foot; nay, sometimes larger, see fig. [110 B p. II], [114 B p. II] and [115 T p. I] which represents three different sizes of the pupil of the eye; the least, was exactly taken from the eye of a large-featur'd man, aged 105, the biggest, from one of twenty, who had this part larger than ordinary, and the other is the common size. If this part of the eye in the pictures of Charles II. and James II. painted by Vandyke at Kensington, were to be measured with a pair of compasses, and compared with their pictures painted by Lilly when they were men, the diameters would be found in both pictures respectively the same. [Illustration: Figs. 110, 114 and 115] In infancy the faces of boys and girls have no visible difference, but as they grow up the features of the boy get the start, and grow faster in proportion to the ring of the eye, than those of the girl, which shews the distinction of the sex in the face. Boys who have larger features than ordinary, in proportion to the rings of their eyes, are what we call manly-featured children; as those who have the contrary, look more childish and younger than they really are. It is this proportion of the features with the eyes, that makes women, when they are dressed in mens-cloaths, look so young and boyish: but as nature doth not always stick close to these particulars, we may be mistaken both in sexes and ages.