OoS REPORT — 1902. 



I dare not assert tliat I have found anything actually novel to bring before you 

 with regard to the atomic theory, but I may say that there has certainly long 

 peemed to me to exist the need to treat it as being a true theory instead of as an 

 hypothesis, and to teach it and discuss it accordingly. 



In thus setting forth what appears to me to be the proper form of the atomic 

 theory, I shall have, at the risk of overtaxing your patience, to restate and 

 examine most of the fundamental and familiar principles of our science in order 

 to illustrate and justify the view I talie. Not only this, but in order as directly 

 and briefly as possible to meet the objection that whatever the atomic theory 

 may be it cannot be introduced to the student of chemical philosopliy in another 

 form than tliat now in use. I shall sometimes have lo adopt, in order to show 

 what can be done, a didactic method which, in most other circura.stnnces, would 

 he quite inexcusable before so distinguished an assembly. 



The atomic theory of chemistry stands unsurpassed for the way in which it 

 has fulfilled the purpose of every great theory, that of giving intellectual mastery 

 of the phenomena of which it treats. But in the form in which it was enun- 

 ciated, and still is universally expressed and accepted, it has the defect of resting 

 upon a metaphysical basis, namely, upon the ancient hypotbesis that bodies are 

 not continuous in texture, but consist of discrete, ultra-minute particles whose 

 properties, if known, would account for those of the bodies themselves. Hence it 

 lias happened that, despite the light it throws upon the relations of chemical phe- 

 nomena and the simple means it aflbrds of expressing these relations, this theory 

 has always been regarded with misgiving, and failed to achieve that explicit recogni- 

 tion which its abounding merit calls for. Indeed, the desire has been expressed to 

 see the time when somethiuo- on a more solid foundation shall have taken its place. 



Now, it is not my intention to discuss the merits or demerits of the atomic 

 liypothesis, which can indeed no longer be treated as a merely metaphysical specu- 

 lation. What I would do to-day is to impress upon you that, in spite of all that 

 has been said and written about the atomic hypothesis in connection with chemistry, 

 the atomic theory propounded by Dalton and adopted, implicitly at least, by all 

 chemists, is not founded upon the metaphysical conception of material discontinuity, 

 and is not explained or illuminated by it. For if that should be the case there 

 will no longer exist any grounds for hesitation in accepting the theory quite ex- 

 plicitly, and then the anomalous condition of things will be removed of a theory 

 being "in universal use without its truth being freely and openly admitted. For 

 the sake of clearness, it is convenient to restrict the term ' atomic hypothesis ' to 

 the old metaphysical view of the discontinuity of matter whilst applying the term 

 ' atomic theory ' to the current elaborated form of the Daltonian theory ; this 

 distinction is adhered to in the present Address. 



In the peroration to liis admirable discourse upon atomic weights or mas.«es 

 delivered before the Chemical Society in ISt'li as the Stas Memorial Lecture 

 Professor Mallet, F.II.S., said : ' By the chemist at his balance the arm of reason 

 is directed into those regions of almost inconceivable minuteness, which lie as far 

 beyond tlie reach of the most powerful microscope as that carries us beyond the 

 reach of the naked eye, quite as impressively as that same arm is stretched forth 

 b'- the astronomer at his divided circle to reach and to weigh the mighty planets 

 that shine in the remotest regions of our solar .«ystem.' On two occasions I have 

 heard the same comparison between the chemist and the astronomer made by Lord 

 Kelvin when lie was in the company of chemists; and undoubtedly both these hiyh 

 authorities have only then expiessed the general view as to the nature of the 

 domain of the chemist. Yet I venture to question whether there is anything in 

 the ways and work of the chemist to support such a view and give point to Mallet 

 and Kelvin's comparison. If, indeed, chemistry is a science which lests upon the 

 atomic hypothesis and, therefore, would cease to exist in the form into which it 

 has developed, should matter prove to be continuous and not discrete, nothing can 

 be said against the view that it is a science of the minute. But I am sure there 

 can be no one ready to maintain that, if the hypothesis of the atomic constitution 

 of substances were an unfounded one, the atomic theory would have been a dis- 

 covery of no great importance ; and Dalton himself, instead of being the founder 



