But
it also happens that both the lines may occupy opposite sides of the'
former canal and be located upon entirely new ground. The distance
between the two lines differs in different germinations and varies from
600 kilometers (360 miles) and more down to the smallest limit at which
two lines may appear separated in large visual telescopes--less than at
intervals of 50 kilometers (30 miles). The breadth of the stripes
themselves may range from the limit of visibility, which we may suppose
to be 30 kilometers (18 miles), up to more than 100 kilometers (60
miles). The color of the two lines varies from black to a light red,
which can hardly be distinguished from the general yellow background of
the continental surface. The space between is for the most part yellow,
but in many cases appears whitish. The gemination is not necessarily
confined only to the canals, but tends to be produced also in the
lakes. Often one of these is seen transformed into two short, broad,
dark lines parallel to one another and traversed by a yellow line. In
these cases the gemination is naturally short and does not exceed the
limits of the original lake.
The gemination is not shown by all at the same time, but when the season
is at hand it begins to be produced here and there, in an isolated,
irregular manner, or at least without any easily recognizable order. In
many canals (such as the Nilosyrtis, for example), the gemination is
lacking entirely, or is scarcely visible.
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