160

The use which I wish to make of this digression is, to ex-
plain the manner of passing the valley by artificial means,
where the road does not require a common bridge, but rather
a via-duct, to ornament the dam or mound of earth thrown
across the valley; and as this must necessarily cause some ob-
struction to the water, I think it might be made subservient to
the other object in view, that of raising the water to a higher
level, instead of digging a deeper channel; thus producing
a continued surface of water in appearance, though in fact the
levels -may be very different.

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