Two years later researches on "Charcoal Vacua" with J.
The invention of the barometer and Torricelli's explanation of the vacuity above the mercury column placed before the members of the Florentine academy a ready method of obtaining vacua; for to exhaust a vessel it was only necessary to join, by means of a tube provided with stopcocks, the vessel to a barometer tube, fill the compound vessel with mercury and then to invert it in a basin containing this liquid, whereupon the mercury column fell, leaving a Torricellian vacuum in the vessel, which could be removed after shutting off the stop-cocks.
For the production of high vacua, see Vacuum Tube; Liquid Gases.
Crookes, who had found that some delicate weighings in vacua were vitiated by this cause.
Hittorf examined the phenomena exhibited in so-called high vacua, that is, in exceedingly rarefied gases.