Fig. 215. View of two Vacuum Pans and their subsidiary Apparatus.

a a. Charging measures, supplied by pipes, which descend from c c, the liquor cisterns. d d, are the vacuum spheroidal pans, the lower half of each being supplied with a jacket, as a case for the steam. At the sides of the neck of each pan are a barometer and thermometer. Below the neck, and just above the horizontal line b b, is the handle of the proof-stick, which appears like a stopcock. When the syrup is sufficiently concentrated, it is discharged into the heater, e e.

This image is from Sugar Cane in Pereira's Elements of Materia Medica and Therapeutics, 1854.