[ [80] To our obtaining a correct idea of the magnitude and distance of any object seen from afar, it is necessary that we consider how much of distinctness an object loses at a distance (from the mere interposition of the air), as well as what it loses in size; and these two considerations must unite before we can decidedly pronounce as to its distance or magnitude. This calculation, as to distinctness, must be made upon the idea that the air is clear, as, if by any accident it is otherwise, we shall (knowing the proportion in which clear air dims a prospect) be led to conclude this farther off than it is, and, to justify that conclusion, shall suppose its real magnitude correspondent with the distance, at which from its degree of distinctness it appears to be. In the circumstance remarked in the text there is, however, a great deception; the fact is, that the colour and the minute parts of the object are lost in the fog, while the size of it is not diminished in proportion; and the eye being accustomed to see objects diminished in size at a great distance, supposes this to be farther off than it is, and consequently imagines it larger.
[ [81] This proposition, though undoubtedly intended to form a part of some future work, which never was drawn up, makes no part of the present.
[ [82] See chap. cccvii.
[ [83] Vide chap. ccxcii. ccciii.
[ [84] See chapter ccxcviii.
[ [85] This was probably to have been a part of some other work, but it does not occur in this.
[ [86] Cento braccia, or cubits. The Florence braccio is one foot ten inches seven eighths, English measure.
[ [87] Probably the Author here means yellow lilies, or fleurs de lis.
[ [88] That point is always found in the horizon, and is called the point of sight, or the vanishing point.
[ [89] See chap. cccxx.