| Dalton's laws of partial pressures are:
1. The vapor pressure, above the surface of a liquid, is independent
of whether the space contains a gas or is a vacuum.
In this apparatus, in the Garland Collection of Classic Physics Apparatus at Vanderbilt University, the two tubes are connected at the bottom. Drops of a liquid are introduced into the rear column, and the corresponding vapor pressure is measured by mercury levels in both columns. As the operation is rather involved, reference is made to the 1875 edition of Ganot's Physics, pp 298-299.
The apparatus was probably obtained by Vanderbilt ca. 1875.