Explanations will be necessary from lecturers and others who give imitations of M. Foucault's ingenuity to render it intelligible to those unacquainted with mathematics, or with the laws of gravity and spherical motion. For instance, it will not be readily understood by every one why the pendulum should vibrate in the same plane, and not partake of the earth's rotation in common with the table; but this could be _shown_ with a bullet suspended by a silkworm's thread. Next, the apparent horizontal revolution of the table round its centre will be incomprehensible to many, as representative of its own and the earth's motion round its axis.
Doubtless we shall soon have public exhibitions of the demonstration in all our cities.
The pendulum is indeed an extraordinary instrument, and has been a useful handmaid to science. We are familiar with it as the time-regulator of our clocks, and the ease with which they may be made to go faster or slower by adjusting its length. But neither this nor the Panthéon elucidation constitutes its sole application. By it the latitude may be approximately ascertained, the density of the earth's strata in different places, and its elliptical eccentricity of figure. The noble Florentine already quoted was its inventor; and it is related of Galileo, while a boy, that he was the first to observe how the height of the vaulted roof of a church might be measured by the times of the vibration of the chandeliers suspended at different altitudes. Were the earth perforated from London to our antipodes, and the air exhausted, a ball dropped through would at the centre acquire a velocity sufficient to carry it to the opposite side, whence it would again descend, and so oscillate forward and backwards from one side of the globe's surface to the other in the manner of a pendulum. Very likely, the Cardinals of the Vatican would deem this heresy, or "flat blasphemy."
A correspondent of the London _Athenæum_, writing from Munich, gives the following account of the festival of the Butchers' Leap in the Fountain: "This strange ceremonial, like the _Schäffler Tanz_, is said to have its origin in the time of the plague. While the Coopers danced with garlands and music through the streets, the Butchers sprang into the fountain in the market-place, to show their fellow-citizens that its water was no longer to be dreaded as poisoned. Perhaps they were the Sanitary Commissioners of those days; and by bathing themselves in the water and dashing it about on the crowd would teach the true means of putting pestilence to flight.