Essai d'une table non-vibrante par enregistrement du mouvement brownien d'un galvanomètre

Abstract

Attempts to attain the natural limit of the sensitivity of a galvanometer, viz. the Brownian movement, have at first been unsuccessful in our institute. Neither a heavy slab of stone attached to an outer wall, nor a masonry of 1800 kg in the cellar embedded in a layer of sand 10 cm thick gave our thermorelais enough stability against the vibrations always present in buildings.

Only by putting the thermorelais on a base with an own frequency much lower than that for which galvanometers are particularly sensitive (some 15 periods per second) we could surmount the difficulties. Such a base, supported by and oscillating freely on four rubber blocs with an oscillating frequency of about 2 periods per second, has been built and described. It has been necessary to lessen its free movements by placing pieces of rubber under the cricks meant for the construction of the whole.

On this table with a weight of 2600 kg the Brownian movement of a galvanometer has been recorded without any interference of the vibrations of the building.