THE subject of the “negative” viscosity of solutions has of late attracted considerable attention. Since the publication of the paper by one of us with Ranken in the Transactions of the Royal Society of Edinburgh, there have appeared a paper by Jones and Veazey, and two by Getman.

Since the latter of the papers by Getman contains a comprehensive review of the older literature on the subject, it is unnecessary for us to do more than indicate those points which are of fundamental importance. First noticed by Hübner in 1873, “negative” viscosity was observed by Sprung in the course of his extensive researches to occur in solutions of several potassium and ammonium salts, while corresponding sodium salts do not cause it. Later investigations added to the salts which are known to give rise to it; mention may be made of hydrobromic acid, in which it occurs at low temperatures but not at higher temperatures, whilst it does not occur at all in the case of hydrochloric acid.