place in that admirable treatise. I have also regarded the whole subject from a stand-point somewhat different from that occupied by the German Professor. To name all the books and journals from which I have derived assistance would be tedious and absurd; they are sufficiently indicated in the notes and references'. I have tried to rest every important statement on firsthand authority. When chemistry is regarded from the point of view of the great workers therein, it wears an aspect very different from that with which it confronts the mere text-book-taster. The book is divided into two parts. The first part is occupied with the statement and discussion of the atomic and molecular theory, and the applications thereof to such subjects as allotropy, isomerism, and the classification of elements and compounds. Somewhat full accounts are also given, in this part, of thermal, optical, and other departments of physical chemistry, in so far as the results and methods of these branches of the science are applicable to the questions regarding the composition of chemical systems which are connoted by the term Chemical Statics. The second part of the book is devoted to the subjects of dissociation, chemical change and equilibrium, chemical affinity, and the relations between chemical action and the distribution of the energy of the changing system. These, and cognate questions, I have ventured to summarise in the expression Chemical Kinetics. I have been much aided in my task by my friends Mr C. Slater, B.A., of St John's College, and Mr R. Threlfall, 1 The full titles of the various journals referred to are given on pp. xxi, xxii. M. C. b B.A., Scholar of Gonville and Caius College. The former has read considerable portions of the proofs and has made many valuable suggestions; the latter has read all, except the first chapter of Book I, and by his criticisms and remarks has helped me to make many important points much clearer and more accurate than they would otherwise have been. M. M. PATTISON MUIR. CAMBRIDGE, October 1884. 56 Limitations to application of law of Dulong and Petit Comparison of law of Avogadro with that of Dulong and Petit as Application of this law to determine values of atomic weights Chemical methods for finding molecular and atomic weights Comparison of chemical with physical methods for determining All reacting bodies in a chemical change influence that change Should the expression nascent action' be retained in chemical Reaction against dualism led by Dumas, Laurent and Gerhardt Further explanation of expression valency of an atom Deduction (from data) of values to be assigned to this constant for different elements Consideration of possible meanings of expression 'bonds' or ‘units Lossen's use of terms monovalent, divalent, &c. Lossen's definitions of these terms Paragraph Page 57 122 General considerations regarding valencies of atoms, especially as these are supposed to be deduced from study of non-gasifiable Atomic groups characteristic of classes of carbon compounds Recapitulation of paragraphs concerning applications of theory of Illustrations of dependence of functions of parts of a molecule on the nature and arrangement, relatively to given parts, of other Illustrations of influence exerted on the function of one atom, or Chemical stability of a molecule is the result of balance between Many physical properties of compounds are also correlated with Thomsen's thermal investigation of the 'dynamical values of the |