(London, Harrison and Sons, 1891). 4to. No wrappers as extracted from ""Philosophical Transactions"" 1890. Vol. 181 - A. Pp. 583-621, textillustrations. Clean and fine.
First appearance of this paper of Thomsons second paper on the electrostatic unit of electricity, in which he corrects some of the imperfections in his first paper on the subject ""On the Determination of the Number of Electrostatic Units in the Electromagnetic Unit of Electricity"" published 1884.