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Class (a) comprises his addresses to the British Association, to the London Mathematical 

 Society, the Rede Lecture at Cambridge, his address at the opening of the Cavendish 

 Laboratory and his Lectures at the Royal Institution and to the Chemical Society. 



Class (6) includes all but one of the articles which he contributed to the Encyclo- 

 pedia Britannica and several others of a kindred character to Nature. 



Class (c) contains such articles as " Faraday " in the Encyclopedia Britannica and 

 "Helmholtz" in Nature. 



Class (d) is chiefly occupied with the reviews of scientific books as they were pub- 

 lished. These appeared in Nature and the most important have been reprinted in these 



In some of these writings, particularly those in class (6), the author allowed himself a 

 greater latitude in the use of mathematical symbols and processes than in others, as 

 for instance in the article " Capillary Attraction," which is in fact a treatise on that subject 

 treated mathematically. The lectures were upon one or other of the three departments 

 of Physics with which he had mainly occupied himself; Colour Perception, Action through 

 a Medium, Molecular Physics; and on this account they are the more valuable. In the 

 whole series of these more popular sketches we find the same clear, graceful delineation of 

 principles, the same beauty in arrangement of subject, the same force and precision in 

 expounding proofs and illustrations. The style is simple and singularly free from any kind 

 of haze or obscurity, rising occasionally, as in his lectures, to a strain of subdued eloquence 

 when the emotional aspects of the subject overcome the purely speculative. 



The books which were written or edited by Maxwell and published in his lifetime but 

 which are not included in this collection were the "Theory of Heat" (1st edition, 1871); 

 "Electricity and Magnetism" (1st edition, 1873); "The Electrical Researches of the Hon- 

 ourable Henry Cavendish, F.R.S., written between 1771 and 1781, edited from the original 

 manuscripts in the possession of the Duke of Devonshire, K.G." (1879). To these may be 

 added a graceful little introductory treatise on Dynamics entitled " Matter and Motion " 

 (published in 1876 by the Society for promoting Christian Knowledge). Maxwell also 

 contributed part of the British Association Report on Electrical Units which was afterwards 

 published in book form by Fleeming Jenkin. 



The "Theory of Heat" appeared in the Text Books of Science series published by 

 Longmans, Green and Co., and was at once hailed as a beautiful exposition of a subject, 

 part of which, and that the most interesting part, the mechanical theory, had as yet but 

 commenced the existence which it owed to the genius and labours of Rankine, Thomson and 

 Clausius. There is a certain charm in Maxwell's treatise, due to the freshness and originality 

 of its expositions which has rendered it a great favourite with students of Heat. 



After his death an " Elementary Treatise on Electricity," the greater part of which he 

 had written, was completed by Professor Garnett and published in 1881. The aim of this 



