1542. In conducting the spectator to view objects, whether by approaches, roads, or walks, it is a matter of some nicety to determine, a priori, the exact distance at which he should be permitted to obtain a full view. There is a certain point of distance from whence every object appears at its greatest magnitude. The apparent height of any object will vary according to its distance, the inclination it makes with the horizon, and our relative elevation or depression. A correspondent of Repton states, that 'any two of the above three things continuing the same, the apparent magnitude will decrease with the third, though not in exact proportion to it. Thus, the object being perpendicular to the horizon, and our elevation remaining the same, its apparent height will decrease with the distance. Our elevation and the distance remaining the same, the apparent height of the object will decrease with its inclination to the horizon. The inclination and distance being the same, the angle, or apparent height, will decrease with our elevation or depression, supposing our height was at first the middle point of the object. This last being liable to some exceptions, the general rule is, that the distance from the object, measured by a perpendicular to it, the point at which its apparent height will be greatest is, where the perpendicular from the eye falls upon the centre.' The apparent height of any object also varies from comparison with the objects around it; and thus a building or tree may look small and insignificant from being seen at the same moment with other buildings or trees of greater magnitude, though if it were seen in any other position, it would appear grand, and would be justly admired. At Holkham, Repton mentions, a lofty obelisk, seen from the portico, appeared to be surrounded by shrubbery, but on a nearer approach he found that these apparent shrubs were really large trees, and only depressed by the greater height of the obelisk. A similar instance, continues Repton, occurs at Welbeck: the large grove of oaks seen from the house across the water, consists of trees remarkable for their straight and lofty trunks, yet, to a stranger, their magnitude is apparently lessened by an enormously large and flourishing ash, which rises like a single tree out of a bank of brushwood. Another instance mentioned by Repton is the lawn at Wentworth House, which, he says, appeared to him circumscribed, and the trees upon it depressed, by four tall obelisks; but as soon as these were removed, the trees assumed a stately appearance, and the lawn seemed of ample dimensions. 'This comparative proportion, or, in other words, this attention to scale or measurement, is not only necessary with regard to objects near each other, but it forms the basis of all improvement depending on perspective, by the laws of which it is well known that objects diminish in apparent size in proportion to their distance.' (Loudon's Repton, p. 135.) Repton mentions several instances in which he has availed himself of the effects of this principle. 'At Hurlingham, on the banks of the Thames,' he observes, 'the lawn in front of the house was necessarily contracted by the vicinity of the river; yet being too large to be kept under the scythe and roller, and too small to be fed by a flock of sheep, I recommended the introduction of Alderney cows only; and the effect is that of giving imaginary extent to the place, which is thus measured below a true standard; because if distance will make a large animal appear small, so the distance will be apparently extended by the smallness of the animal.' (Ibid. p. 136.)
