Page 94 [94]
52 LIGHT AND WATER
strokes on their further sides." The characteristic of
moving water is indeed to insist upon the vertical and
ignore the horizontal lines of the image, though very
regular ripples in the foreground often seem to con¬
tradict this principle by showing horizontal lines that
do not exist in the object at all. The reflexion of the
sunset sky in Plate X XI affords a striking instance of
an apparent exception of this kind, the cloud forms
being broken up horizontally by the extremely gentle
motion of the water. Plate XXII, in which the
ripples are fairly regular and travelling obliquely,
shows the characteristic “ markings " formed on their
farther sides by the reflexion of the dark wooded
bank.
But it will, no doubt, have been noticed that these
horizontal strokes often take the form of elongated
rings. In Plate XXIV the reflexion of the distant
and nearly horizontal bank is seen to consist of a
number of very flat rings. When the spectator’s posi¬
tion is not too low, so that the whole surface of a wave
is in view, as when looking from Q, Fig. 14, there
are generally ¢wo points on each wave at which a
suitably placed luminous point, such as P, can be seen
reflected. Thus, on the farther side of the first wave,
P appears by reflexion at I and H, and on the second
wave,at G and F. Beyond X, the two points are on
the near side of each wave, viz., D and C on the
fourth, and B and A on the fifth wave.2 Now if, in
‘ Compare also the rippled surfaces in Plates XII and XIII, page
44, and in Plates XVII and XVIII, page 50.
" Ina sine curve (page 31) the two points of each pair would be
proportionally farther apart than in the circular curve of the diagram.