The apparent shape of the ground will be altered by the situation of the spectator. This is a subject of much importance to the landscape gardener, although not generally studied. In hilly countries, where the banks are bold, a road in a valley is always pleasing, because it seems natural, and carries with it the idea of ease and safety; but, in a country that is not hilly, we ought rather to shew the little * inequalities of ground to advantage. The difference betwixt viewing ground from the bottom of a valley, or the side of a hill, will be best explained by the following diagram [fig. 47], where the rules of perspective again assist the scientific improver.
The spectator at A, in looking up the hill towards c, will lose all the ground that is foreshortened; and every object which rises higher than five feet (i. e. the height of his eye), will present itself above his horizon, if the slope is exactly an inclined plane, or hanging level; but as the shape of ground here delineated more frequently occurs, he will actually see the sky, and, consequently, the utmost pitch of the hill, beneath the body of the animal placed at B, and part of the thorn at c, become invisible. This accounts for the highest mountains losing their importance, when seen only from the base; while, on the contrary, a plain or level surface (for instance the sea) appears to rise considerably when viewed from an eminence. Let us suppose another spectator to be placed at D, it is evident that this person will see no ground foreshortened but that below him, while the opposite hill will appear to him far above the head of the man at A, and above the cow at B. In the section, the dotted lines are the respective horizons of the two spectators, and the sketches shew the landscape seen by each, in which the forked tree may serve as a scale to measure the height of each horizon.
*[That I may not be misunderstood, as recommending a road over hill and dale to shew the extent or beauty of a place, I must here observe, that nothing can justify a visible deviation from the shortest line, in an approach to a house, but such obstacles as evidently point out the reason for the deviation.]
