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Carnot's, 161 et seq.Projectiles, the effects of the impact of, 310, 327-328;seen with the naked eye, 311, 317;measuring the velocity of, 332;photography of, 309-337.Prony's brake, 132.Proof, nature of, 284.Prophesying events, 220 et seq.Psalms, quotation from the, 89.Pseudoscope,

The pseudoscope which produces effects opposite to those of the stereoscope is an interesting device.

Of course in this practical age the inquiry is put—Of what use is the stereoscope or pseudoscope?

With respect to the pseudoscope—which makes the outside of a teacup appear as the inside, and the inside as the outside; which transforms convexity into concavity, and the reverse; and a sculptured face into a hollow mask; which makes the tree in your garden appear inside your room, and the branches farthest off come nearest to the eye; and which, when you look at your pictures, represents them as sunk into a deep recess in the wall,—with respect to this instrument, its practical uses have yet to be discovered.