Chap. CCCXVII.—Of Towns and other Buildings seen through a Fog in the Morning or Evening.
Buildings seen afar off in the morning or in the evening, when there is a fog, or thick air, shew only those parts distinctly which are enlightened by the sun towards the horizon; and the parts of those buildings which are not turned towards the sun remain confused and almost of the colour of the fog.
Chap. CCCXVIII.—Of the Height of Buildings seen in a Fog.
Of a building near the eye the top parts will appear more confused than the bottom, because there is more fog between the eye and the top than at the base. And a square tower, seen at a great distance through a fog, will appear narrower at the base than at the summit. This is accounted for in Chapter cccxiii. which says, that the fog will appear whiter and thicker as it approaches the ground; and as it is said before[79], that a dark object will appear smaller in proportion as it is placed on a whiter ground. Therefore the fog being whiter at bottom than at top, it follows that the tower (being darkish) will appear narrower at the base than at the summit.
Chap. CCCXIX.—Why Objects which are high, appear darker at a Distance than those which are low, though the Fog be uniform, and of equal Thickness.
Amongst objects situated in a fog, thick air, vapour, smoke, or at a distance, the highest will be the most distinctly seen: and amongst objects equal in height, that placed in the darkest fog, will be most confused and dark. As it happens to the eye H, looking at A B C, three towers of equal height; it sees the top C as low as R, in two degrees of thickness; and the top B, in one degree only; therefore the top C will appear darker than the top of the tower B.
