In the thermo-regulators which have been constructed heretofore, the heat has been regulated by the variation in the inflow of gas to the heating flame. The apparatus described below, and shown in the accompanying cut, taken from the Zeitschrift fur Instrumentenkunde, operates on an entirely different principle. The distillation and condensation process of a fluid heated to the boiling point in the vessel, A, is as follows:

The steam passes first through the pipes, a and c, into the serpentine tube, where it is condensed, and then flows through the tubes, d and b, back into the vessel, A, if the cock, r, is closed, but if the said cock is open, it flows into the receptacle, K. When the liquid begins to boil the steam passes freely through the tubes, d and b, part passing through the tube, f, out into the air, and the other part passing through the open cock, r, to the receptacle, K; but the condensed liquid soon closes these passages to the steam. At h is an opening for a thermometer, t, and through this opening the liquid can be poured into the vessel, A. If the cock, r, is kept closed, the volume of liquid in the vessel, A, cannot be diminished, and the bath, B, must take the constant and uniform temperature of the steam in the vessel, A, as the vessel, B, is heated evenly on all sides.

This apparatus can also be used as an air bath, in which case the vessel, B, is left empty and closed by a suitable stopper.