In 1826 the idea occurred to him of attacking this problem by means of pendulum experiments at the top and bottom of a deep mine.
On the pendulum was fixed an illuminated silver bead which appeared as a bright point of light when seen for an instant.
No resolution could withstand it; in that dreamy mood losing all consciousness, at last my soul went out of my body; though my body still continued to sway as a pendulum will, long after the power which first moved it is withdrawn.
Below this pendulum let there be placed another coil through which passes the current to be measured; then when currents pass through these coils the pendulum of the second clock will be either accelerated or retarded relatively to the other clock, since the action of gravity is supplemented by that of an electric attraction or repulsion between the coils.
In a refined form this method is often employed for measuring the intensity of a magnetic field at a given place, just as the intensity of gravity at different parts of the earth is deduced from observations of the rate at which a pendulum of known length vibrates.
My job is to make sure the pendulum never swings too far into the court of the Black God.
In the Agamennone seismometrograph the pendulum is cheese-shaped, and weighs 500 kilos in one form and 2000 kilos, or over two tons, in the largest.
For his demonstration in 1851 of the diurnal motion of the earth by the rotation of the plane of oscillation of a freely suspended, long and heavy pendulum exhibited by him at the Pantheon in Paris, and again in the following year by means of his invention the gyroscope, he received the Copley medal of the Royal Society in 1855, and in the same year he was made physical assistant in the imperial observatory at Paris.
This type of apparatus has been replaced in Japan by what are called duplex pendulum seismographs.
Such a pendulum can be set in vigorous vibration even by feeble puffs of air directed against it, provided these are administered exactly in time with the natural period of vibration of the pendulum.