It was for some time under consideration by the friends Of Professor Maxwell, whether the ms. Should be published in its fragmentary form or whether it should be completed by another hand, so as to carry out as far as possible the author's original design; but before any decision had been arrived at it was suggested that the book might be made to serve the purposes of students by a selection of Articles from Professor Maxwell's Electricity and Magnetism, so as to make it in a sense complete for the portion of the subject covered by the first volume of the last-mentioned work. In accordance with this suggestion, a number of Articles have been selected from the larger book and reprinted. These are indicated by a after the number of the Article. Arts. 93 — 98 and 141 are identical with Arts. 118 — 123 and 58 of the larger treatise, but these have been reprinted in accordance with directions con tained in Professor Maxwell's ms.