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A footprint of brontozoum giganeum, a now extinct relative of the cassowary. This example is eighteen inches in length, the bird was believed to weigh between four and eight hundred pounds.

Footprint of brontozoum giganteum

A footprint of brontozoum giganeum, a now extinct relative of the cassowary. This example is eighteen…

A mark, indentation, figure, etc., produced by pressure.

Dental Cup for Impression

A mark, indentation, figure, etc., produced by pressure.

"Let S be the position of the spectator; O and B the position of distant objects. The rays O R and B R which proceed from them, strike the surface of the water very obliquely, and the light which is reflected in the direction R S is sufficient to make a sensible impression upon the eye. But in regard to objects such as A placed near the spectator, they are not seen reflected, because the rays A R' which proceed from them strike the water with but little obliquity; and consequently, the part of their light which is reflected in the direction R' S, towards the spectator, is not sufficient to produce a sensible impression upon the eye." —Wells, 1857

Reflection

"Let S be the position of the spectator; O and B the position of distant objects. The rays O R and B…

"Here, of the rays S A, S B, and S C, only the ray S C meets the eye of the spectator D. The spot C, therefore, will appear luminous to the spectator D, but no other spot of the water A B C." —Wells, 1857

Reflection

"Here, of the rays S A, S B, and S C, only the ray S C meets the eye of the spectator D. The spot C,…