The Present State of Chemical Nomenclature, by Prof. A. W. Williamson, Ph.D., F.R.S.—The author stated there were perhaps few departments of science in which such definite principles had been adopted, and to a great extent this applied to the formation of names, as in their own science of chemistry. The practice of stating in a name as briefly as possible certain facts, and as a rule important facts, had been, as every chemist I new, the chief object of their nomenclature. But he thought he might be permitted to say that if one looked to the composition of any result like the present nomenclature of chemistry which had been guided by intellectual principles—it was of immense importance to consider its purely intellectual principles, viz., the principles of convenience, and perhaps even of popular tastes, and, if he might be allowed to imagine such a thing, even the prejudices which occasionally arose among a great number of men who adopted any particular form of expression. He proposed to refer to the question from the different points of view. If they had occasion to consider, without knowing anything about it, what was the most important condition to which every name ought to conform, he fancied there would be no two opinions on the matter. The first and most important condition and requirement of every name of a thing that was important was that it should call to the minds of those “who used it, without ambiguity, some one particular thing or one particular idea. He should be inclined to consider a code of laws by which their action would be rendered uniform with regard to names, and which would establish such fundamental principles that an absence of ambiguity would be secured. The more any name could be defined and shortened the better it would be for chemistry. In the modern progress of chemistry, especially in that department of which the growth had been enormously great—he meant the many carbon compounds—the purpose of obtaining clearness and avoiding ambiguity in the nomenclature had been, with few exceptions, satisfactorily attained. But he thought members would agree with him that in the names given to some compounds more complex than others the chief object of convenience had not been attained to an equal extent. They found names given which, when carefully considered by chemist?, told a story, but a very long story, and in a manner which was really free from ambiguity, but only by aid of a great number of syllables, and a compound word of inconvenient length was this attained. On the other hand, amongst very common substances that systematic process had been, he thought, to a considerably less degree adopted. The older names of commoner substances, such as salts, were to a great extent based upon facts which were true, but were by no means the only facts to be recalled. Of course every chemist knew the great number of names that were in common use, and how far they served to recall a particular process, but only one among many processes by which the substance could be formed. On the other hand, many names had grown up from bodies which were purely empirical—names which did not recall any particular properties, but served with great convenience and without ambiguity to indicate the body. If they looked to the circumstances which affected that one condition which he had submitted as essential to names being perfectly free from ambiguity, there was perhaps hardly one condition more practically important than this, that there should be in the names as little change as possible, and more especially was this the case when a name that had once been given had come to be used in relation to particular substances. It was within the memory of chemists that changes of name had taken place not only when a particular substance was recalled, but there were also a considerable number of cases showing that the name given at one time to one body was afterwards given to another. The circumstances attending such changes were in some instances of an exceedingly reasonable kind, and well worthy of consideration after it was found that there were grounds for believing that the names belonged more properly to other substances. If, however, changes introduced confusion, they were necessarily injurious to the progress of the science. When he looked back to the successive steps by which their knowledge had risen to its present position, and to the ideas that had succeeded one another, he felt that in order to really understand chemistry, and to be able to arrange the facts in a convenient order, they must see how they had grown up. If that was important in practical matters, it was even more important in what he might call the scientific work. He ventured to think, at all events he had always felt, that to use with safety any idea that they were accustomed to use, it was almost essential, and was certainly of importance, that they should endeavour to trace the origin and growth of that idea, so as to see what it really meant. His object in bringing the subject before the Section was to obtain from his colleagues and friends their views on the present state of matters, and to give them the opportunity of considering together—those who more especially felt it their duty to contribute by any means in their i power to the advancement of science either in guiding the operations or growth of those names—whether there could not be greater concert among chemists as to what was being and what had been done, so that they might conform their doings to certain laws. He had frequently seen with regret some features in chemical nomenclature that had been springing up of late years. He had seen some habits gaining ground which appeared to be at variance with the best principles of nomenclature—he would assume such to be the case. But there were laws in the growth of those words, and he could not doubt for his own part that if chemists came to recognise those laws, or rid themselves of them, the future growth of words would gradually come to be a more systematic guide. It had sometimes been felt that to attempt to solve the problem would be useless, and that irregularities had become so prevalent that it would be hopeless to think they could ever remedy them. But he thought differently, and would urge that in the direction he had pointed out they were only now beginning to move. There was only one convenient division among names. That division, of course, was not absolute, because no such division could be absolute; but the great majority of names were used to denote things and ideas. Some names were of little use in relation to the particular ideas, and therefore it seemed to him that the best way to obtain a name was as the result of experiment. If founded on that principle there could be no ambiguity. At the present time, as their -views had considerably changed, and as they had not attained finality in their operations, there was much to be learnt, and it was reasonable to suppose that if they adopted a particular name to indicate a particular thing it might perhaps turn out at some time hence an error upon which people would look back as historical. With regard to names, especially theories, there were some of them that had certainly served important purposes. It -was then really essential to the arrangement of their ideas that they should for the time imagine something to exist, and that they should recall by some convenient name that which they assumed or imagined. Names, in his opinion, ought to express ideas; but there were many names introduced which he thought were used for no better purpose than to express the absence of ideas. It often happened that when exploring any particular part of a field, they got a rational clue which led them clearly and well for a certain way; and they failed to follow it further. The cases were numberless, but one of the most important was that of chemical combination itself. Complex bodies were far more numerous than the few simple bodies with which they had to do, and while in the habit of using the term chemical combination, they had concealed their ignorance of the state of combination. Others used the term molecular combination, and there again they concealed their ignorance of the bodies to which it was applied. Among the present anomalies in names there was one which he ventured to submit to the consideration of the Section, and which had grown up to some extent of late, and that was the replacing of empirical names of things by names, which, while he would call them rational, because they served to recall intelligibly and without ambiguity, served to recall the number of atoms. He mentioned such cases by way of illlustrating the ractice which had seemed to him to be gaining ground of late years, for the purpose, as some said, of increasing the clearness of statement. He had no doubt that the words were framed for the purpose of conveying to the mind something useful to know, and as names formed on that principle had been found to be based on those superseded by others, he thought when they came to such names as indicated molecular composition k was better to avoid them, because, as he had said, they had not arrived at finality. The chemists of fifty years ago were as confident as chemists of the present day in the matter of nomenclature; and therefore the more they could obtain names without ambiguity and without liability to change in the future, the more probable was it that such names would stand and continue to be used. A crowd of material presented itself just then to his mind, but he did not think it would be well to trouble the Section with further remarks. He merely wished to throw out the ball for his colleagues to deal with.