Laplace, therefore, laid the responsibility of the acceleration upon the moon, and if his views were correct, the tidal retardation must either be insignificant in amount, or be counteracted by some other agency.

The dark appearance on the screen corresponding to the thinnest part of the film is probably due to refraction of the ray of light reflected from the second surface, consequent in its passing from a rare into a denser medium, and again from the denser medium into the rare, which refraction Lord Rayleigh considers to effect a retardation equivalent to half a wave length.

We see in the Porter scene in Macbeth a suspension of this nature; but Shakespeare used it sparingly, unless, indeed, we are to consider as a deliberate point of art the retardation of movement commonly observable in the fourth acts of his tragedies.

Our great astronomer, Adams, however, appears to have found a flaw in Laplace's calculation, and to have shown that only half the observed retardation could be accounted for in the way he had suggested.

The slightest possible retardation at its close brought us to the refrain of the simple adagio, interrupted again by a rush of violoncello-notes, rapid and low, like some sudden under-current striving to burst through the frozen sweetness.

Among the former were the successive retardations of seasons in successive descents, amounting to about four months at the depth of 25 feet; and the successive diminutions of the annual range of temperature.

It moves, for a time, with great velocity and vigour, but the force of the first impulse is perpetually decreasing, and though it should encounter no obstacle capable of quelling it by a sudden stop, the resistance of the medium through which it passes, and the latent inequalities of the smoothest surface, will, in a short time, by continued retardation, wholly overpower it.

Cornu, in answering the objection that there may be an unknown retardation by reflection from the distant mirror, says that if such existed the error it would introduce in his own work would be only 1/7000 that of Foucault, on account of the great distance used, and on account of there being in his own experiments but one reflection instead of twelve.