Isobath Constant Level Inkstand

Brass and metal Isobath constant level inkwell by Thomas De La Rue boasts a mechanism for maintaining the ink level with a float made of hard rubber. As the ink level goes down, the float (attached to the glass ends) rotates to maintain a constant level in the dipping spout. The knob at the top unscrews for filling. The design includes a pen holder and carry handle.

An advertisement (pictured) gives an illustration of the inner workings and describes the advantages:

“The float is so weighted and poised as always to keep the ink on the same level, whatever quantity may be contained in the reservoir.”

“Advantages: the ink in the dipping-well is always maintained at the same uniform depth. The reservoir being completely enclosed, the ink is protected from dust and evaporation. The ink remains clear and limpid to the last drop, even after the lapse of several months, saving of ink and of time and trouble in cleaning and replenishing”.