August 25, 1892] 



NA TURE 



409 



can make into caibonates, into what classes of molecales a cer- 

 tain larger fragrment of carbonic acid can be formed, the 

 incomplete records of these things already run through a great 

 many volumes. These carboxylic bodies are open to productive 

 studies, stimulated by various sorts of inquiry and demands of 

 life. Such have been the gatherings of research. They have 

 been slowly drawn into order, more slowly interpreted in mean- 

 ing. The advance has been constant, deliberate, sometimes 

 in doubt, always persisting and gradually gaining firmer ground. 

 So chemistry has reached the period of definition. Its guiding 

 theory has come to be realized, 



" The atomic theory " has more and more plainly appeared to 

 be the central and vital truth of chemical science. As a work- 

 ing hypothesis it has directed abstruse research through difficult 

 ways to open accomplishment in vivid reality. As a system of 

 knowledge, it has more than kept pace with the rate of inven- 

 tion. As a philosophy, it is in touch with profound truth in 

 physics, in the mineral kingdom, and in the functions of living 

 bodies. As a language it has been a necessity of man in dealing 

 with chemical events. Something might have been done, no 

 doubt, without it, had it been possible to keep it out of the 

 chemical mind. But with a knowledge of the primary elements 

 of matter, as held at the beginning of this century, some theory 

 of chemical atoms was inevitable. And whatever theory might 

 have been adapted, its use in investigation would have drawn it 

 with a certainty into the essential features of the theory now 

 established. It states the constitution of matter in terms that stand 

 for things as they are made. The mathematician may choose 

 the ratio of numerical notation, whether the ratio often or some 

 other. But the chemist must find existing ratios of atomic and 

 molecular mass, with such degree of exactness as he can attain. 

 Chemical notation, the index of the atomic system, is imperfect, 

 as science is incomplete. However defective, it is the resultant 

 of a multitude of facts. The atomic theory has come to be more 

 than facile language, more than lucid classification, more than 

 working hypothesis, it is the definition of the knoiun truth in the 

 existence of matter. 



The chemical atom is known, however, for what it does, 

 rather than for what it is. It is known as a centre of action, a 

 factor of influence, an agent of power. It is identified by its 

 responses, and measured by its energies. Concealed as it is, 

 each atom has given proof of its own part in the structure of a 

 molecule. Proofs of position, not in space but in action, as re- 

 lated to other atoms, have been obtained by a multitude of 

 workers with the greatest advantage. The arrangement of the 

 atoms in space, however, is another and later question, not in- 

 volved in the general studies of structure. But even this ques- 

 tion has arisen upon its own chemical evidences, for certain 

 bodies, so that the "configuration " of the molecule has become 

 an object of active research. 



Known for what it does, the atom is not clearly known for 

 what it is. Chemists, at any rate, are concerned mainly with 

 what can be made out of atoms, not with what atoms can be made 

 of. Whatever they are, and by whatever force or motion it is 

 that they unite with each other, we define them by their effects. 

 Through their effects they are classified in the rank and file 

 of the periodic system. The physicists, however, do not stop 

 short of the philosophical study of the atom itself. As a vibra- 

 tory body its movements have been under mathematical calcula- 

 tions ; as a vortex ring its pulsations have been assumed to agree 

 with its combining power. As an operating magnet its inter- 

 action with other like magnets has been predicated as the method 

 of valence. There are, as I am directly assured, physicists of 

 penetration and prudence now looking with confidence to studies 

 of the magnetic relations of atoms to each other. ^ Moreover, 

 another company of workers, the chemists of geometric iso- 

 merism, assume a configuration of the atoms, in accord with that 

 of the molecule. 



The stimulating truth of the atomic constitution of the mole- 

 cule, a great truth in elastic touch with all science, excites 

 numerous hypotheses, which, however profitable they may be, 

 are to be stoutly held at a distance from the truth itself. Such 

 are the hypotheses of molecular aggregation into crystals and 

 other mineral forms. Such are the biological theories of mole- 

 cules polymerizing Into cells, and of vitality as a chemical pro- 

 perty of the molecule. Such are the questions of the nature of 

 atoms, and the genesis of the elements as they are now known, 



' " The results of molecular physics point unmistakably to the atom as a 

 magnet, in its chemical activities."— A. E. Dolbear, in a personal commu- 

 nication. 



NO. 119 1, VOL. 46] 



questions on the border of metaphysics. Let all these be held 

 distinct from the primary law of the atomic constitution of 

 simple molecules in gaseous bodies, an essential principle in an 

 exact science. The chemist should have the comfortable assur- 

 ance, every day, as he plies his balance of precision, that the 

 atom-made molecules are there, in their several ratios of quan- 

 tity, however many unsettled questions may lie around about 

 them. Knowledge of molecular structure makes chemistry a 

 science, nourishing to the reason, giving dominion over matter, 

 for beneficence to life. 



Every chemical pursuit receives strength from every advance 

 in the knowledge of the molecule. And to this knowledge, 

 none the less, every chemical pursuit contributes. The analysis 

 of a mineral, whether done for economic ends or not, may 

 furnish a distinct contribution toward atomic valence. The 

 further examination of steel in the cables of a suspension bridge 

 is liable to lead to unexpected evidence upon polymeric unions. 

 Rothamsted farm, where ten years is not a long time for the 

 holding of an experiment, yields to us a classic history of the 

 behaviour of nitrogen, a history from which we correct our theories. 

 The analysis of butter for its substitutes has done something to 

 set us right upon the structure of the glycerides. Clinical in- 

 spection of the functions of the living body fain finds a record of 

 molecular transformations too difficult for the laboratory. The 

 efforts of pharmaceutical manufacture stimulate new orders of 

 chemical combination. The revision of the pharmacopcea every 

 ten years points out a humiliating number of scattered errors in the 

 published constants on which science depends. The duty of the 

 engineer, in his scrutiny of the quality of lubricating oils, brings 

 a more critical inquiry into the laws of molecular movement. 

 There is not time to mention the many professions and pursuits 

 of men who contribute toward the prituiples of chemistry and 

 hold a share therein. If it be the part of pure science to find 

 the law of action in nature, it is the part of applied science both 

 to contribute facts and to put theory to the larger proof. In the 

 words of one who has placed industry in the greatest of its debts 

 to philosophic research, W. H. Perkin, " There is no chasm 

 between pure and applied science, they do not even stand side 

 by side, but are linked together." So in all branches of chemis- 

 try, whether it be termed applied or not, the best workers are 

 most strongly bound as one, in their dependence upon what is the 

 known of the structure of the molecule. 



Studies of structure were never before so inviting. In this 

 direction and in that especial opportunities appear. Moreover 

 the actual worker here and there breaks into unexpecte d paths^ 

 of promise. Certainly the sugar group is presenting to the 

 chemist an open way from simple alcohols on through to the 

 cell substances of the vegetable world. And nothing anywhere 

 could be more suggestive than the extremely simple unions of 

 nitrogen lately discovered. They are likely to elucidate link- 

 ings of this element in great classes of carbon compounds, all 

 significant in general chemistry. Then certain comparative 

 studies have new attractions. As halogens have been upon 

 trial side by side with each other, so for instance silicon must be 

 put through its paces with carbon, and phosphorus with nitrogen. 

 Presently, also, the limits of molecular mass, in polymers and in 

 unions with water, are to be nearer approached from the chemi- 

 cal side, as well as from the side of physics, in that attractive but 

 perplexing border ground between affinity and the states of 

 ^gregation. 



Such is the extent and such the diversity of chemical labour 

 at present that every man must put limits to the range of his 

 study. The members of a society or section of chemistry, com- 

 ing together to hear each other's researches, are better able, for 

 the most part, to listen for instruction than for criticism. Still 

 less prepared for hasty judgment are those who do not come 

 together in societies at all. Even men of eminent learning 

 must omit large parts of the subject, if it be permitted to speak 

 of chemistry as a single subject. These considerations admonish 

 us to be liberal. When metallurgical chemistry cultivates 

 scepticism as to the work upon atomic closed chains, it is a 

 culture not the most liberal. When a devotee of organic syn- 

 thesis puts a low value upon analytic work, he takes a very 

 narrow view of chemical studies. When the chemist who 

 is in educational service disparages investigations done in in- 

 dustrial service, he exercises a pitiful brevity of wisdom. 



The pride of pure science is justified in this, that its truth is 

 for the nurture of man. And the ambition of industrial art is 

 honoured in this, its skill gives strength to man. It is the 

 obligation of science to bring the resources of the earth, its. 



