So that generally the bow
is less than a semicircle, and never more. He says he has seen it more
than a semicircle. I have often seen the leg of the bow below my level.
My situation at Monticello admits this, because there is a mountain
there in the opposite direction of the afternoon's sun, the valley
between which and Monticello is five hundred feet deep. I have seen a
leg of a rainbow plunge down on the river running through the valley.
But I do not recollect to have remarked at any time, that the bow was
more than half a circle. It appears to me, that these facts demolish the
Newtonian hypothesis, but they do not support that erected in its stead
by the Abbe. He supposes a cloud between the sun and observer, and that
through some opening in that cloud, the rays pass, and form an iris on
the opposite part of the heavens, just as a ray passing through a hole
in the shutter of a darkened room, and falling on a prism there, forms
the prismatic colors on the opposite wall. According to this, we might
see bows of more than the half circle, as often as of less. A thousand
other objections occur to this hypothesis, which need not be suggested
to you.
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