The simple “submerged bulblet” apparatus for determining vapour pressures, previously described in these Proceedings (vol. xxx. p. 437), may be modified to assume the form shown in fig. 1. The substance, solid or liquid, is placed in the bulb A of this dynamic isoteniscope. The advantages gained are, that the new apparatus may be used for high pressures, that the confining fluid (bulb B) is reduced in amount, and that the thermometer is inserted directly in the bath and its bulbis, is therefore, no longer in a region of varying pressures (Proc, p. 436).