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 Science. 
 
 MANCHESTER, 1887. 
 
 ADDRESS 
 
 SIR HENRY E. ROSCOE, 
 
 n 
 
 M.P., D.C.L., LL.D., Ph.D., F.R.S., V.P.C.S., 
 PRESIDENT. 
 
 Manchester, distingaished as the birthplace of two of the greatest 
 discoveries of modern science, heartily welcomes to-day for the third time 
 the members and friends of the British Association for the Advancement 
 of Science. 
 
 On the occasion of our first meeting in this city in the year 1842 the 
 President, Lord Francis Egerton, commenced his address with a touching 
 allusion to the veteran of science, John Dalton, the great chemist, the 
 discoverer of the laws of chemical combination, the framer of the atomic 
 theory upon which the modern science of chemistry may truly be said to 
 be based. Lord Francis Egerton said : ' Manchester is still the residence 
 of one whose name is uttered with respect wherever science is cultivated, 
 who is here to-night to enjoy the honours due to a long career of persever- 
 ing devotion to knowledge, and to receive from myself, if he will con- 
 descend to do so, the expression of my own deep personal regret that 
 increase of years, which to him up to this hour has been but increase of 
 wisdom, should have rendered him in respect of mere bodily strength un- 
 able to fill on this occasion an office which in his case would have received 
 more honour than it could confer. I do regret that any cause should have 
 prevented the present meeting in his native town from being associated 
 with the name * — and here I must ask you to allow me to exchange the 
 name of Dalton in 1842 for that of Joule in 1887, and to add again in the 
 words of the President of the former year that I would gladly have served 
 as a doorkeeper in any house where Joule, the father of science in Man- 
 chester, was enjoying his just pre-eminence. 
 
 For it is indeed true that the mantle of John Dalton has fallen on the 
 shoulders of one well worthy to wear it, one to whom science owes a debt 
 1887. A 
 
2 REPORT— 1887. 
 
 of gratitude not less than that which it willingly pays to the memory of 
 the originator of the atomic theory. James Prescott Joule it was who, 
 in his determination of the mechanical equivalent of heat, about the very 
 year of our first Manchester meeting, gave to the world of science the 
 results of experiments which placed beyond reach of doubt or cavil the 
 greatest and most far-reaching scientific principle of modern times, 
 namely, that of the conservation of energy. This, to nse the words of 
 Tyndall, is indeed a generalisation of conspicuous grandeur fit to take 
 rank with the principle of gravitation, more momentous, if that be possible, 
 combining as it does the energies of the material universe into an organic 
 whole, and enabling the eye of science to follow the flying shuttles of the 
 universal power as it weaves what the Erdgeist in ' Faust ' calls ' the 
 living garment of God.' 
 
 It is well, therefore, for us to remember, in the midst of the turmoil 
 of our active industrial and commercial life, that Manchester not only well 
 represents the energy of England in these practical directions, but that 
 it possesses even higher claims to our regard and respect as being the seat 
 of discoveries of which the value not only to pure science is momentous, 
 but which also lie at the foundation of all our material progress and all our 
 industrial success. For without a knowledge of the laws of chemical com- 
 bination all the marvellous results with which modern industrial chemistry 
 has astonished the world could not have been achieved, whilst the know- 
 ledge of the quantitative relations existing between the several forms of 
 energy, and the possibility of expressing their amount in terms of ordinary 
 mechanics, are matters which now constitute the life-breath of every 
 branch of applied science. For example, before Dalton's discovery every 
 manufacturer of oil of vitriol — a substance now made each week in thou- 
 sands of tons within a few miles of this spot — every manufacturer had his 
 own notions of the quantity of sulphur which he ought to bum in order to 
 make a certain weight of sulphuric acid, but he had no idea that only a 
 given weight of sulphur can unite with a certain quantity of oxygen 
 and of water to form the acid, and that an excess of any one of the com- 
 ponent parts was not only useless but harmful. Thus, and in tens of 
 thousands of other instances, Dalton replaced rule of thumb by scientific 
 principle. In like manner the applications of Joule's determination of the 
 mechanical equivalent of heat are even more general ; the increase and 
 measurement of the efficiency of our steam engines and the power of our 
 dynamos are only two of the numerous examples which might be adduced 
 of the practical value of Joule's work. 
 
 If the place calls up these thoughts, the time of our meeting also 
 awakens memories of no less interest, in the recollection that we this 
 year celebrate the Jubilee of her Most Gracious Majesty's accession to 
 the throne. It is right that the members of the British Association for 
 the Advancement of Science should do so with heart and voice, for 
 although science requires and demands no royal patronage, we thereby 
 express the feeling which must be uppermost in the hearts of all men of 
 
 LOAN STACK 
 
ADDRESS. 3 
 
 science, the feeling of thankfulness that we have lived in an age which 
 has witnessed an advance in onr knowledge of nature, and a consequent 
 improvement in the physical, and let us trust also in the moral and 
 intellectual, well being of the people hitherto unknown ; an age with 
 which the name of Victoria will ever be associated. 
 
 To give even a sketch of this progress, to trace even in the merest 
 outline the salient points of the general history of science during the 
 fifty momentous years of her Majesty's reign, is a task far beyond my 
 limited powers. It must suffice for me to point ont to you, to the best 
 of my ability, some few of the steps of that progress as evidenced in 
 the one branch of science with which I am most familiar, and with which 
 I am more closely concerned, the science of chemistry. 
 
 In the year 1837 chemistry was a very different science from that 
 existing at the present moment. Priestley, it is true, had discovered 
 oxygen, Lavoisier had placed the phenomena of combustion on their true 
 basis, Davy had decomposed the alkalis, Faraday had liquefied many of 
 the gases, Dalton had enunciated the laws of chemical combination by 
 weight, and Gay Lussac had pointed out the fact that a simple volumetric 
 relation governs the combination of the gases. But we then possessed no 
 knowledge of chemical dynamics, we were then altogether unable to 
 explain the meaning of the heat given off in the act of chemical combina- 
 tion. The atomic theory was indeed accepted, but we were as ignorant 
 of the mode of action of the atoms and as incapable of explaining their 
 mutual relationship as were the ancient Greek philosophers. Fifty years 
 ago, too, the connection existing between the laws of life, vegetable and 
 animal, and the phenomena of inorganic chemistry, was ill understood. 
 The idea that the functions of living beings are controlled by the same 
 forces, chemical and physical, which regulate the changes occurring in 
 the inanimate world, was then one held by only a very few of the foremost 
 thinkers of the time. Vital force was a term in everyone's mouth, an 
 expression useful, as Goethe says, to disguise our ignorance, for 
 
 Wo die BegriflFe fehlen, 
 Da tritt ein Wort zur rechten Zeit sich ein. 
 
 Indeed the pioneer of the chemistry of life, Liebig himself, cannot quite 
 shake himself free from the bonds of orthodox opinion, and he who first 
 placed the phenomena of life on a true basis cannot trust his chemical 
 principles to conduct the affairs of the body, but makes an appeal to vital 
 force to help him out of his difficulties ; as when in the body politic an 
 unruly mob requires the presence and action of physical force to restrain 
 it and to bring its members under the saving influence of law and order, so 
 too, according to Liebig's views, in the body corporeal a continual conflict 
 between the chemical forces and the vital power occurs throughout life, 
 in which the latter, when it prevails, insures health and a continuance of 
 life, but of which defeat insures disease or death. The picture presented 
 to the student of to-day is a very different one. We now believe that no 
 
 .... A 2 
 
 169 
 
4 REPORT— 1887. 
 
 such conflict is possible, but that life is governed by chemical and 
 physical forces, even though we cannot in every case explain its phenomena 
 in terms of these forces ; that whether these tend to continue or to end 
 existence depends upon their nature and amount, and that disease and 
 death are as much a consequence of the operation of chemical and 
 physical laws as are health and life. 
 
 Looking back again to our point of departure fifty years ago, let us for 
 a moment glance at Dalton's labours, and compare his views and those of 
 his contemporaries with the ideas which now prevail. In the first place it 
 is well to remember that the keystone of his atomic theory lies not so 
 much in the idea of the existence and the indivisible nature of the 
 particles of matter — though this idea was so firmly implanted in his mind 
 that, being questioned on one occasion on the subject, he said to his friend 
 the late Mr. Ransome, ' Thou knowst it must be so, for no man can split 
 an atom ' — as in the assumption that the weights of these particles are 
 different. Thus whilst each of the ultimate particles of oxygen has the 
 same weight as every other particle of oxygen, and each atom of hydrogen, 
 for example, has the same w^eight as every other particle of hydrogen, the 
 oxygen atom is sixteen times heavier than that of hydrogen, and so on 
 for the atoms of every chemical element, each having its own special 
 weight. It was this discovery of Dalton, together with the further one 
 that the elements combine in the proportions indicated by the relative 
 weights of their atoms or in multiples of these proportions, which at 
 once changed chemistry from a qualitative to a quantitative science, 
 making the old invocation prophetic, ' God created all things according to 
 measure and to weight.' 
 
 The researches of chemists and physicists during the last fifty years 
 have not only strengthened but broadened the foundations of the great 
 Manchester philosopher's discoveries. It is true that his original 
 numbers, obtained by crude and inaccurate methods, have been replaced 
 by more exact figures, but his laws of combination and his atomic 
 explanation of those laws stand as the great bulwarks of our science. 
 
 On the present occasion it is interesting to remember that within a 
 stone's-throw of this place is the small room belonging to our Literary 
 and Philosophical Society which served Dalton as his laboratory. Here 
 with the simplest of all possible apparatus — a few cups, penny ink bottles, 
 rough balances, and self-made thermometers and barometers — Dalton 
 accomplished his great results. Here he patiently worked, marshalling 
 facts to support his great theory, for as an explanation of his laborious 
 experimental investigations the wise old man says : * Having been in my 
 progress so often misled, by taking for granted the results of others, I 
 have determined to write as little as possible but what I can attest by 
 my own experience.' Nor ought we when here assembled to forget that 
 the last three of Dalton's experimental essays — one of which, on a new 
 method of measuring water of crystallisation, contained more than the 
 germ of a great discovery — were communicated to our Chemical Section 
 
ADDRESS. a 
 
 in 1842, and that this was the last memorable act of his scientific life. 
 In this last of his contributions to science, as in his first, his method of 
 procedure was that which has been marked out as the most fruitful by 
 almost all the great searchers after nature's secrets, namely the assump- 
 tion of a certain view as a working hypothesis, and the subsequent in- 
 stitution of experiment to bring this hypothesis to a test of reality upon 
 which a legitimate theory is afterwards to be based. * Dalton,' as Henry 
 well says, * valued detailed facts mainly, if not solely, as the stepping- 
 stones to comprehensive generalisations.' 
 
 Next let us ask what light the research of the last fifty years has 
 thrown on the subject of the Daltonian atoms : first, as regards their 
 size ; secondly, in respect to their indivisibility and mutual relationships ; 
 and thirdly, as regards their motions. 
 
 As regards the size and shape of the atoms, Dalton ofi'ered no opinion, 
 for he had no experimental grounds on which to form it, believing 
 that they were inconceivably small and altogether beyond the grasp of 
 our senses aided by the most powerful appliances of art. He was in the 
 habit of representing his atoms and their combinations diagrammatically 
 as round discs or spheres made of wood, by means of which he was fond of 
 illustrating his theory. But such mechanical illustrations are not without 
 their danger, for I well remember the answer given by a pupil to a 
 question on the atomic theory : ' Atoms are round balls of wood invented 
 by Dr. Dalton.' So determinedly indeed did he adhere to his mechanical 
 method of representing the chemical atoms and their combinations that he 
 could not be prevailed upon to adopt the system of chemical formulae 
 introduced by Berzelius and now universally employed. In a letter 
 addressed to Graham in April 1837 he writes : ' Berzelius' symbols are 
 horrifying. A young student in chemistry might as soon learn Hebrew 
 as make himself acquainted with them.' And again : * They appear 
 to me equally to perplex the adepts in science, to discourage the learner, 
 as well as to cloud the beauty and simplicity of the atomic theory.' 
 
 But modern research has accomplished, as regards the size of the 
 atom, at any rate to a certain extent, what Dalton regarded as impossible. 
 Thus in 1865 Loschmidt, of Vienna, by a train of reasoning which I 
 cannot now stop to explain, came to the conclusion that the diameter of an 
 atom of oxygen or nitrogen was 10.000,000 of ^ centimetre. With the 
 highest known magnifying power we can distinguish the lo^ P^-rt of a 
 centimetre ; if now we imagine a cubic box each of whose sides has the 
 above length, such a box when filled with air will contain from 60 to 100 
 millions of atoms of oxygen and nitrogen. A few years later William 
 Thomson extended the methods of atomic measurement, and came to the 
 conclusion that the distance between the centres of contiguous molecules is 
 less than 5000,000 ^^^ greater than f;ooo;ooo;ooo o^ ^ centimetre ; or, to put 
 it in language more suited to the ordinary mind, Thomson asks us to 
 imagine a drop of water magnified up to the size of the earth, and then 
 tolls us that the coarseness of the graining of such a mass would be 
 
6 REPORT — 1887. 
 
 something between a heap of small shot and a heap of cricket balls. Or 
 again, to take Clifford's illustration, you know that our best microscopes 
 magnify from 6,000 to 8,000 times ; a microscope which would magnify 
 that result as much again would show the molecular structure of water. 
 Or again, to put it in another form, if we suppose that the minutest organ- 
 ism we can now see were provided with equally powerful microscopes, 
 these beings would be able to see the atoms. 
 
 Next, as to the indivisibility of the atom, involving also the question 
 as to the relationships between the atomic weights and properties of the 
 several elementary bodies. 
 
 Taking Dalton's aphorism, ' Thou knowst no man can split an atom,* 
 as expressing the view of the enunciator of the atomic theory, let us see 
 bow far this idea is borne out by subsequent work. In the first place, 
 Thomas Thomson, the first exponent of Dalton's generalisation, was torn 
 by conflicting beliefs until he found peace in the hypothesis of Prout, that 
 the atomic weights of all the so-called elements are multiples of a com- 
 mon unit, which doctrine he sought to establish, as Thorpe remarks, by 
 some of the very worst quantitative determinations to be found in chemi- 
 cal literature, though here I may add that they were not so incorrect as 
 Dalton's original numbers. 
 
 Coming down to a somewhat later date, Grraham, whose life was devoted 
 to finding what the motion of an atom was, freed himself from the bond- 
 age of the Daltonian aphorism, and defined the atom not as a thing which 
 cannot be divided, but as one which has not been divided. With him, as 
 with Lucretius, as Angus Smith remarks, the original atom may be far 
 down. 
 
 But speculative ideas respecting the constitution of matter have been 
 the scientific relaxation of many minds from olden time to the present. In 
 the mind of the early Greek the action of the atom as one su?bstance 
 taking various forms by unlimited combinations was sufficient to account 
 for all the phenomena of the world. And Dalton himself, though up- 
 holding the indivisibility of his ultimate particles, says : ' We do not 
 know that any of the bodies denominated elementary are absolutely in- 
 decomposable.' Again Boyle, treating of the origin of form and quality, 
 says : ' There is one universal matter common to all bodies— an extended 
 divisible and impenetrable substance.' Then Graham in another place 
 expresses a similar thought when he writes : ' It is conceivable that 
 the various kinds of matter now recognised as different elementary sub- 
 stances may possess one and the same ultimate or atomic molecules exist- 
 ing in different conditions of movement. The essential unity of matter 
 is an hypothesis in harmony with the equal action of gravity upon all 
 bodies.' 
 
 What experimental evidence is now before us bearing upon these 
 interesting speculations ? In the first place, then, the space of fifty years 
 has completely changed the face of the inquiry. Not only has the number 
 of distinct well-established elementary bodies increased from fifty-three in 
 
ADDRESS. 7 
 
 1837 to seventy in 1887 (not includiDg the twenty or more new elementfi 
 recently said to have been discovered by Kriiss andNilson in certain rare 
 Scandinavian minerals), but the properties of these elements have been 
 studied, and are now known to us with a degree of precision then undreamt 
 of. So that relationships existing between these bodies which fifty years 
 ago were undiscernible are now clearly manifest, and it is to these relation- 
 ships that I would for a moment ask your attention. I have already stated 
 that Dalton measured the relative weights of the ultimate particles by 
 assuming hydrogen as the unit, and that Prout believed that on this 
 basis the atomic weights of all the other elements would be found to be 
 multiples of the atomic weight of hydrogen, thus indicating that an inti- 
 mate constitutional relation exists between hydrogen and all the other 
 elements. 
 
 Since the days of Dalton and Prout the truth or otherwise of Prout's 
 law has been keenly contested by the most eminent chemists of all 
 countries. The inquiry is a purely experimental one, and only those who 
 have a special knowledge of the difficulties which surround such in- 
 quiries can form an idea of the amount of labour and self-sacrifice borne by 
 such men as Dumas, Stas, and Alarignac in carrying out delicate researches 
 on the atomic weights of the elements. What is, then, the result of these 
 most laborious experiments ? It is that, whilst the atomic weights of the 
 elements are not exactly either multiples of the unit or of half the unit, 
 many of the numbers expressing most accurately the weight of the atom 
 approximate so closely to a multiple of that of hydrogen that we are con- 
 strained to admit that these approximations cannot be a mere matter of 
 chance, but that some reason must exist for them. What that reason is, 
 and why a close approximation and yet something short of absolute iden- 
 tity exists, is as yet hidden behind the veil ; but who is there that doubts 
 that when this Association celebrates its centenary this veil will have been 
 lifted and this occult but fundamental question of atomic philosophy 
 shall have been brought into the clear light of day ? 
 
 But these are by no means all the relationships which modern science 
 has discovered with respect to the atoms of our chemical elements. So 
 long ago as 1829 Dobereiner pointed out that certain groups of elements 
 exist presenting in all their properties strongly marked family character- 
 istics, and this was afterwards extended and insisted upon by Dumas. We 
 find, for example, in the well-known group of chlorine, bromine, and 
 iodine, these resemblances well developed, accompanied moreover by 
 a proportional graduation in their chemical and physical properties. 
 Thus, to take the most important of all their characters, the atomic 
 weight of the middle term is the mean of the atomic weights of the two 
 extremes. But these groups of triads appeared to be unconnected in any 
 way with one another, nor did they seem to bear any relation to the far 
 larger number of the elements not exhibiting these peculiarities. 
 
 Things remained in this condition until 1863, when Newlands threw 
 fresh light upon the subject, showing a far-reaching series of relation- 
 
8 REPOBT — 1887. 
 
 ships. For the first time we thus obtained a glance into the mode in 
 which the elements are connected together, but, like so many new dis- 
 coveries, this did not meet with the recognition which we now see it de- 
 serves. But whilst England thus had the honour of first opening up this 
 new path, it is to Germany and to Russia that we must look for the con- 
 summation of the idea. Germany, in the person of Lothar Meyer, keeps, 
 as it is wont to do, strictly within the limits of known facts. Russia, in 
 the person of Mendelejeff, being of a somewhat mere imaginative nature, 
 not only seizes the facts which are proved, but ventures upon prophecy. 
 These chemists, amongst whom Carnelley must be named, agree in placing 
 all the elementary bodies in a certain regular sequence, thus bringing 
 to light a periodic recurrence of analogous chemical and physical pro- 
 perties, on account of which the arrangement is termed the periodic 
 system of the elements. 
 
 In order to endeavour to render this somewhat complicated matter 
 clear to you, I may perhaps be allowed to employ a simile. Let us, if you 
 please, imagine a series of human families, a French one, represented by 
 Dumas, an English one, by name Newlands, a German one, the family of 
 Lothar Meyer, and lastly a Russian one, that of Mendelejefi". Let us next 
 imagine the names of these chemists placed in a horizontal line in the order 
 I have mentioned. Then let us write under each the name of his father, 
 and again, in the next lower line, that of his grandfather, followed by that 
 of his great-grandfather, and so on. Let us next write against each of 
 these names the number of years which has elapsed since the birth of the 
 individual. We shall then find that these numbers regularly increase by 
 a definite amount, i.e., by the average age of a generation, which will be 
 approximately the same in all the four families. Comparing the ages of 
 the chemists themselves we shall observe certain differences, but these are 
 small in comparison with the period which has elapsed since the birth of 
 any of their ancestors. Now each individual in this series of family trees 
 represents a chemical element ; and just as each family is distinguished 
 by certain idiosyncrasies, so each group of the elementary bodies thus 
 arranged shows distinct signs of consanguinity. 
 
 But more than this, it not unfrequently happens that the history and 
 peculiarities of some member of a family may have been lost, even if the 
 memory of a more remote and more famous ancestor may be preserved, 
 although it is clear that such an individual must have had an existence. 
 In such a case Francis Galton would not hesitate from the characteristics 
 of the other members to reproduce the physical and even the mental 
 peculiarities of the missiug member; and should genealogical research 
 bring to light the true personal appearance and mental qualities of the 
 man, these would be found to coincide with Galton 's estimate. 
 
 Such predictions and such verifications have been made in the case 
 of no less than three of oar chemical elements. Thus, Mendelejeff pointed 
 out that if, in the future, certain lacunae in his table were to be filled, 
 they must be filled by elements possessing chemical and physical pro- 
 
ADDRESS. ' 9 
 
 perties which he accurately specified. Since that time these gaps have 
 actually been stopped by the discovery of Gallium by Lecoq de Boisbau- 
 dron, of Scandium by Nilson, and of Germanium by Winkler, and their 
 properties, both physical and chemical, as determined by their discoverers, 
 agree absolutely with those predicted by the Russian chemist. Nay, 
 more than this, we not unfrequently have had to deal with chemical 
 foundlings, elements whose parentage is quite unknown to us. A careful 
 examination of the personality of such waifs has enabled us to restore them 
 to the family from which they have been separated by an unkind fate, and 
 to give them that position in chemical society to which they are entitled. 
 
 These remarkable results, though they by no means furnish a proof of 
 the supposition already referred to, viz., that the elements are derived 
 from a common source, clearly point in this direction, and lend some 
 degree of colour to the speculations of those whose scientific imagination, 
 wearying of dry facts, revels in picturing to itself an elemental Bathybius, 
 and in applying to the inanimate, laws of evolution similar to those which 
 rule the animate world. Nor is there wanting other evidence regarding 
 this inquiry, for here heat, the great analyser, is brought into court. The 
 main portion of the evidence consists in the fact that distinct chemical in- 
 dividuals capable of existence at low temperatures are incapable of exist- 
 ence at high ones, but split up into new materials possessing a less com- 
 plicated structure than the original. And here it may be well to empha- 
 sise the distinction which tlie chemist draws between the atom and the 
 molecule, the latter being a more or less complicated aggregation of 
 atoms, and especially to point out the fundamental difference between the 
 question of separating the atoms in the molecule and that of splitting 
 up the atom itself. The decompositions above referred to are, in fact, not 
 confined to compound bodies, for Victor Meyer has proved in the case of 
 iodine that the molecule at high temperatures is broken to atoms, and 
 J. J. Thomson has added to our knowledge by showing that this breaking 
 up of the molecule may be effected not only by heat vibrations, but 
 likewise by the electrical discharge at a comparatively low temperature. 
 
 How far, now, has this process of simplification been carried ? Have 
 the atoms of our present elements been made to yield ? To this a negative 
 answer must undoubtedly be given, for even the highest of terrestrial 
 temperatures, that of the electric spark, has failed to shake any one of these 
 atoms in two. That this is the case has been shown by the results 
 with which spectrum analysis, that new and fascinating branch of science, 
 has enriched our knowledge, for that spectrum analysis does give 
 us most valuable aid in determining the varying molecular conditions of 
 matter is admitted by all. Let us see how this bears on the question of 
 the decomposition of the elements, and let us suppose for a moment that 
 certain of our present elements, instead of being distinct substances, were 
 made up of common ingredients, and that these compound elements, if 
 I may be allowed to use so incongruous a term, are split up at the 
 temperature of the electric spark into less complicated molecules. Then 
 
 A 3 
 
10 REPORT — 1887. 
 
 the spectroscopic examination of such a body must indicate the existence 
 of these common ingredients by the appearance in the spark spectra of 
 these elements of identical bright h'nes. Coincidences of this kind have 
 indeed been observed, but on careful examination these have been shown 
 to be due either to the presence of some one of the other elements as an 
 impurity or to insufficient observational power. This absence of coinci- 
 dent lines admits, however, of two explanations — either that the elements 
 are nob decomposed at the temperature of the electric spark, or, what 
 appears to me a much more improbable supposition, each one of the 
 numbers of bright lines exhibited by every element indicates the existence 
 of a separate constituent, no two of this enormous number being identical. 
 Terrestrial analysis having thus failed to furnish favourable evidence, 
 we are compelled to see if any information is forthcoming from the 
 chemistry of the sun and stars. And here I would remark that it is not 
 my purpose now to dilate on the wonders which this branch of modern 
 science has revealed. It is sufficient to remind you that chemists thus 
 have the means placed at their disposal of ascertaining with certainty the 
 presence of elements well known on this earth in fixed stars so far dis- 
 tant that we are now receiving the light which emanated from them 
 perhaps even thousands of years ago. 
 
 Since Bunsen and Kirchhoflf 's original discovery in 1859, the labours 
 of many men of science of all countries have largely increased our know- 
 ledge of the chemical constitution of the sun and stars, and to no one 
 does science owe more in this direction than to Lockyer and Huggins in 
 this country, and to Young in the New England beyond the seas. 
 Lockyer has of late years devoted his attention chiefly to the varying 
 nature of the bright lines seen under different conditions of time and 
 place on the solar surface, and from these observations he has drawn 
 the inference that the matching observed by KirchhoflF between, for 
 instance, the iron lines as seen in our laboratories and those visible in 
 the sun, has fallen to the ground. He further explains this want of 
 uniformity by the fact that at the higher transcendental temperatures of 
 the sun the substance which we know here as iron is resolved into separate 
 components. Other experimentalists, however, while accepting Lockyer's 
 facts as to the variations in the solar spectrum, do not admit his conclu- 
 sions, and would rather explain the phenomena by the well-known differ- 
 ences which occur in the spectra of all the elements when their molecules 
 are subject to change of temperature or change of position. 
 
 Further, arguments in favour of this idea of the evolution of the 
 elements have been adduced from the phenomena presented by the 
 spectra of the fixed stars. It is well known that some of these shine with a 
 white, others with a red, and others again with a blue light ; and the 
 spectroscope, especially under the hands of Huggins, has shown that the 
 chemical constitution of these stars is different. The white stars, of 
 which Sirius may be taken as a type, exhibit a much less complicated 
 spectrum than the orange and the red stars ; the spectra of the latter 
 
ADDRESS. 11 
 
 remind us more of those of the metalloids and of chemical compounds 
 than of the metals. Hence it has been argued that in the white, presum- 
 ably the hottest, stars a celestial dissociation of our terrestrial elements 
 may have taken place, whilst in the cooler stars, probably the red, com- 
 bination even may occur. But even in the white stars we have no direct 
 evidence that a decomposition of any terrestrial atom has taken place ; 
 indeed we learn that the hydrogen atom, as we know it here, can endure 
 unscathed the inconceivably fierce temperature of stars presumably many 
 times more fervent than our sun, as Sirius and Vega. 
 
 Taking all these matters into consideration, we need not be surprised 
 if the earthbound chemist should, in the absence of celestial evidence 
 which is incontestable, continue, for the present at least, and until fresh 
 evidence is forthcoming, to regard the elements as the unalterable founda- 
 tion stones upon which his science is based. 
 
 Pursuing another line of inquiry on this subject, Crookes has added a 
 remarkable contribution to the question of the possibility of decomposing 
 the elements. With his well-known experimental prowess, he has 
 discovered a new and beautiful series of phenomena, and has shown that 
 the phosphorescent lights emitted by certain chemical compounds, espe- 
 cially the rare earths, under an electric discharge in a high vacuum ex- 
 hibit peculiar and characteristic lines. For the purpose of obtaining his 
 material Crookes started from a substance believed by chemists to be 
 homogeneous, such, for example, as the rare earth yttria, and succeeded 
 by a long series of fractional precipitations in obtaining products which 
 yield different phosphorescent spectra, although when tested by the 
 ordinary methods of what we may term high temperature spectroscopy, 
 they appear to be the one substance employed at the starting point. The 
 other touchstone by which the identity, or otherwise, of these /arious pro- 
 ducts might be ascertained, viz., the determination of their atomic weights, 
 has not, as yet, engaged Crookes' attention. In explanation of these sin- 
 gular phenomena, the discoverer suggests two possibilities. First, that 
 the bodies yielding the different phosphorescent spectra are different ele- 
 mentary constituents of the substance which we call yttria. Or, if this 
 be objected to because they all yield the same spark spectrum, he adopts 
 the very reasonable view that the Daltonian atom is probably, as we have 
 seen, a system of chemical complexity ; and adds to this the idea that 
 these complex atoms are not all of exactly the same constitution and 
 weight, the differences, however, being so slight that their detection has 
 hitherto eluded our most delicate tests, with the exception of this one of 
 phosphorescence in a vacuum. To these two explanations, Marignac, in 
 a discussion of Crookes' results, adds a third. It having been shown 
 by Crookes himself that the presence of the minutest traces of foreign 
 bodies produce remarkable alterations in the phosphorescent spectra, 
 Marignac suggests that in the course of the thousands of separations 
 which must be made before these differences become manifest, traces of 
 foreign bodies may have been accidentally introduced, or, being present 
 
12 EEPORT— 1887. 
 
 in the original material, may have accumulated to a different extent in 
 the various fractious, their presence being indicated by the only test by 
 which they can now be detected. Which of these three explanations is 
 the true one must be left to future experiment to decide. 
 
 We mast now pass from the statics to the dynamics of chemistry ; that 
 is, from the consideration of the atoms at rest to that of the atoms in 
 motion. Here again we are indebted to John Dalton for the first step 
 in this direction, for he showed that the particles of a gas are constantly 
 flying about in all directions; that is, that gases diffuse into one another, 
 as an escape of coal gas from a burner, for example, soon makes itself 
 perceptible throughout the room, Dalton, whose mind was constantly 
 engaged in studying the molecular condition of gases, first showed that 
 a light gas cannot rest upon a heavier gas as oil upon water, but that an 
 in terpen etration of each gas by the other takes place. It is, however, to 
 Graham's experiments, made rather more than half a century ago, that 
 we are indebted for the discovery of the law regulating these molecular 
 motions of gases, proving that their relative rates of diffusion are inversely 
 proportional to the square roots of their densities, so that oxygen being 16 
 times heavier than hydrogen, their relative rates of diffusion are 1 and 4. 
 
 But whilst Dalton and Graham indicated that the atoms are in a con- 
 tinual state of motion, it is to Joule that we owe the first accurate deter- 
 mination of the rate of that motion. At the Swansea Meeting in 1848, 
 Joule read a paper before Section A on the Mechanical Equivalent of 
 Heat and on the Constitution of Elastic Fluids. In this paper Joule 
 remarks that whether we conceive the particles to be revolving round 
 one another according to the hypothesis of Davy, or flying about in 
 every direction according to Herapath's view, the pressure of the gas will 
 be in proportion to the vis viva of its particles. ' Thus it may be shown 
 that the particles of hydrogen at the barometrical pressure of 30 inches 
 at a temperature of 60° must move with a velocity of 6225 54 feet per 
 second in order to produce a pressure of 14*714 lbs. on the square inch ; ' 
 or, to put it in other words, a molecular cannonade or hailstorm of parti- 
 cles, at the above rate — a rate, we must remember, far exceeding that 
 of a cannon ball — is maintained against the bounding surface. 
 
 We can, however, go a step further and calculate with Clerk Maxwell 
 the number of times in which this hydrogen molecule, moving at the rate 
 of 70 miles per minute, strikes against others of the vibrating swarm, 
 and we learn that in one second of time it must knock against others no 
 less than 18 thousand million times. 
 
 And here we may pause and dwell for a moment on the reflection that 
 in nature there is no such thing as great or small, and that the structure of 
 the smallest particle, invisible even to our most searching vision, may be 
 as complicated as that of any one of the heavenly bodies which circle round 
 our sun. 
 
 But how does this wonderful atomic motion affect our chemistry ? 
 Can chemical science or chemical phenomena throw light upon this 
 
ADDRESS. 13 
 
 motion, or can tbis motion explain any of the known phenomena of onr 
 science ? I have already said that Lavoisier left untouched the dynamics 
 of combustion. He could not explain why a fixed and unalterable amount 
 of heat is in most cases emitted but in some cases absorbed when 
 chemical combination takes place. What Lavoisier left unexplained 
 Joule has made clear. On August 25, 1843, Joule read a short communi- 
 cation, I am glad to remember, before the Chemical Section of our 
 Association, meeting that year at Cork, containing an announcement of 
 a discovery which was to revolutionise modern science. This consisted 
 in the determination of the mechanical equivalent of heat, in proving by 
 accurate experiment that the expenditure of energy equal to that developed 
 by the weight of 772 pounds falling through one foot at Manchester, the 
 temperature of one pound of water can be raised 1° Fahrenheit. In 
 other words, every change in the arrangement of the particles is accom- 
 panied by a definite evolution or an absorption of heat. In all such cases 
 the molecular energy leaves the potential to assume the kinetic form, 
 or vice versa. Heat is evolved by the clashing of the atoms, and this 
 amount is fixed and definite. 
 
 Thus it is to Joule we owe the foundation of chemical dynamics and the 
 basis of thermal chemistry. As the conservation of mass or the principle 
 of the indestructibility of matter forms the basis of chemical statics, so 
 the principle of the conservation of energy ^ constitutes the foundation 
 of chemical dynamics. Change in the form of matter and change in the 
 form of energy are the universal accompaniments of every chemical 
 operation. Here again it is to Joule we owe the proof of the truth of 
 this principle in another direction, viz., that when electrical energy is 
 developed by chemical change a corresponding quantity of chemical 
 energy disappears. Energy as defined by Maxwell is the power of doing 
 work, and work is the act of producing a change of configuration in a 
 system in opposition to a force which resists that change. Chemical 
 action produces such a change of configuration in the molecules. Hence, 
 as Maxwell says, *a complete knowledge of the mode in which the 
 potential energy of a system varies with the configuration would enable 
 us to predict every possible motion of the system under the action of 
 given external forces, provided we were able to overcome the purely 
 mathematical difficulties of the calculation.' The object of thermal 
 chemistry is to measure these changes of energy by thermal methods, 
 and to connect these with chemical changes, to estimate the attractions 
 of the atoms and molecules to which the name of chemical affinity has 
 been applied, and thus to solve the most fundamental problem of 
 chemical science. How far has modern research approached the solution 
 of this most difficult problem ? How far can we answer the question, 
 
 ' * The total energy of any material system is a quantity which can neither be 
 increased nor diminished by any action between the parts of the system, though it 
 may be transformed into any of the forms of which energy is susceptible.' — JUax- 
 
 WELL. 
 
 A 5 
 
14 REPORT — 1887. 
 
 what is the amonnt of the forces at work in these chemical changes ? 
 What laws govern these forces ? Well, even in spite of the results with 
 which recent researches, especially the remarkable ones of the Danish 
 philosopher Thomson have enriched us, we must acknowledge that we 
 are yet scarcely in sight of Maxwell's position of successful prediction. 
 Thermal chemistry, we must acknowledge, is even yet in its infancy ; it 
 is, however, an infant of sturdy growth, likely to do good work in the 
 world, and to be a credit to him who is its acknowledged father, as well 
 as to those who have so carefully tended it in its early years. 
 
 But recent investigation in another direction bids fair even to eclipse 
 the results which have been obtained by the examination of thermal 
 phenomena. And this lies in the region of electrical chemistry. 
 Faraday's work relating to conductivity of chemical substances has been 
 already referred to, and this has been since substantiated and extended 
 to pure substances by Kohlrausch. It has been shown, for example, that 
 the resistance of absolutely pure water is almost an infinite quantity. 
 But a small quantity of an acid, such as acetic or butyric acid, greatly 
 increases the conductivity ; but more than this, it is possible by determi- 
 nation of the conductivity of a mixture of water with these two acids to 
 arrive at a conclusion as to the partition of the molecules of the water 
 between the acids. Such a partition, however, implies a change of 
 position, and therefore we are famished with a means of recognising the 
 motion of the molecules in a liquid, and of determining its amount. 
 Thus it has been found that the hindrance to molecular motion is more 
 affected by the chemical character of the liquid than by physical 
 characters such as viscosity. We have seen that chemical change is 
 always accompanied by molecular motion, and further evidence of the 
 truth of this is gained from the extraordinary chemical inactivity of pure 
 unmixed substances. Thus pure anhydrous hydrochloric acid does not 
 act upon lime, whereas the addition of even a trace of moisture sets up a 
 most active chemical change, and hundreds of other examples of a similar 
 kind might be stated. Bearing in mind that these pure anhydrous com- 
 pounds do not conduct, we are led to the conclusion that an intimate 
 relation exists between chemical activity and conductivity. And we need 
 not stop here; for a method is indicated indeed by which it will be 
 possible to arrive at a measure of chemical affinity from determination 
 of conductivity. It has indeed been already shown that the rate of 
 change in the saponification of acetic ether is directly proportional to the 
 conductivity of the liquid employed. 
 
 Such wide-reaching inquiries into new and fertile fields, in which we 
 seem to come into nearer touch with the molecular state of matter, and 
 within a measurable distance of accurate mathematical expression, leads 
 to confident hope that Lord Rayleigh's pregnant words at Montreal may 
 ere long be realised : * It is from the further study of electrolysis that we 
 may expect to gain improved views as to the nature of chemical reactions, 
 and of the forces concerned in bringing them about ; and I cannot help 
 
ADDRESS. 1 5 
 
 thinking that the next great advance, of which we already have some 
 foreshadowing, will come on this side.' 
 
 There is, perhaps, no branch of our science in which the doctrine of 
 the Daltonian atom plays a more conspicuous part than in organic chemis- 
 try or the chemistry of the carbon compounds, as there is certainly none 
 in which such wonderful progress has been made during the last fifty 
 years. One of the most striking and perplexing discoveries made rather 
 more than half a century ago was that chemical compounds could exist 
 which, whilst possessing an identical chemical composition, that is con- 
 taining the same percentage quantity of their constituents, are essentially 
 distinct chemical substances exhibiting different properties. Dalton was 
 the first to point out the existence of such substances, and to suggest that 
 the difference was to be ascribed to a different or to a multiple arrange- 
 ment of the constituent atoms. Faraday soon afterwards proved that this 
 supposition was correct, and the research of Liebig and Wohler on the 
 identity of composition of the salts of fulminic and cyanic acid gave 
 further confirmation to the conclusion, leading Faraday to remark that 
 * now we are taught to look for bodies composed of the same elements in 
 the same proportion but diff'ering in their qualities, they may probably 
 multiply upon us.' How true this prophecy has become we may gather 
 from the fact that we now know of thousands of cases of this kind, and 
 that we are able not only to explain the reason of their difference by 
 virtue of the varying position of the atoms within the molecule, but even 
 to predict the number of distinct variations in which any given chemical 
 compound can possibly exist. How large this number may become may 
 be understood from the fact that, for example, one chemical compound, 
 a hydrocarbon containing thirteen atoms of carbon combined with twenty- 
 eight atoms of hydrogen, can be shown to be capable of existing in no less 
 than 802 distinct forms. 
 
 Experiment in every case in which it has been applied has proved the 
 truth of such a prediction, so that the chemist has no need to apply the 
 cogent argument sometimes said to be used by experimentalists enamoured 
 of pet theories, * When facts do not agree with theory, so much the worse 
 for the facts ! * This power of successful prediction constitutes a high- 
 water mark in science, for it indicates that the theory upon which such a 
 power is based is a true one. 
 
 But if the Daltonian atom forms the foundation of this theory, it is 
 upon a knowledge of the mode of arrangement of these atoms and on a 
 recognition of their distinctive properties that the superstructure of 
 modern organic chemistry rests. Certainly it does appear almost to 
 verge on the miraculous that chemists should now be able to ascertain 
 with certainty the relative position of atoms in a molecule so minute 
 that millions upon millions, like the angels in the schoolmen's dis- 
 cussion, can stand on a needle's point. And yet this process of orientation 
 is one which is accomplished every day in our laboratories, and one which 
 more than any other has led to results of a startling character. Still, this 
 
16 HEPORT— 1887. 
 
 sword to open tlie oyster of science would have been wanting to ns if we 
 had not taken a step farther than Dalton did, in the recognition of the 
 distinctive natnre of the elemental atoms. We now assume on good 
 grounds that the atom of each element possesses distinct capabilities of 
 combination ; some a single capability, others a double, others a triple, 
 and others again a fourfold combining capacity. The germs of this theory 
 of valency, one of the most fruitful of modern chemical ideas, were 
 enunciated by Frankland in 1852, but the definite explanation of the 
 linking of atoms, of the tetrad nature of the carbon atoms, their power of 
 combination, and of the difference in structure between the fatty and aro- 
 matic series of compounds, was first pointed out by Kekule in 1857; though 
 we must not forget that this great principle was foreshadowed so long ago 
 as 1833 from a physical point of view by Faraday in his well-known 
 laws of electrolysis, and that it is to Helmholtz in his celebrated Faraday 
 lecture that we owe the complete elucidation of the subject ; for, whilst 
 Faraday has shown that the number of the atoms electroly tically deposited 
 is in the inverse ratio of their valencies, Helmholtz has explained this by the 
 fact that the quantity of electricity with which each atom is associated is 
 directly proportional to its valency. 
 
 Amongst the tetrad class of elements, carbon, the distinctive element 
 of organic compounds, finds its place ; and the remarkable fact that the 
 number of carbon compounds far exceeds that of all the other elements 
 put together receives its explanation. For these carbon atoms not only 
 possess four means of grasping other atoms, but these four-handed carbon 
 atoms have a strong partiality for each other's company, and readily 
 attach themselves hand in hand to form open chains or closed rings to 
 which the atoms of other elements join to grasp the unoccupied carbon 
 hand, and thus to yield a dancing company in which all hands are locked 
 together. Such a group, each individual occupying a given position with 
 reference to the others, constitutes the organic molecule. When, in 
 such a company, the individual members change hands, a new combination 
 is formed. And as in such an assembly the eye can follow the changing 
 positions of the individual members, so the chemist can recognise in his 
 molecule the position of the several atoms, and explain by this the fact 
 that each arrangement constitutes a new chemical compound possessing 
 different properties, and account in this way for the decompositions which 
 each differently constituted molecule is found to undergo. 
 
 Chemists are, however, not content with representing the arrangement 
 of the atoms in one plane, as on a sheet of paper, but attempt to express 
 the position of the atoms in space. In this way it is possible to explain 
 certain observed differences in isomeric bodies which otherwise baffled our 
 efforts. To Van t'Hoff, in the first instance, and more recently to 
 Wislicenus, chemistry is indebted for work in this direction, which throws 
 light on hitherto obscure phenomena, and points the way to still further 
 and more important advances. 
 
 It is this knowledge of the mode in which the atoms in the molecule 
 
ADDRESS. 17 
 
 are arranged, this power of determiDing the nature of this arrangement, 
 which has given to organic chemistry the impetus which has overcome 
 so many experimental obstacles, and given rise to such unlooked-for 
 results. Organic chemistry has now become synthetic. In 1837 we were 
 able to build up but very few and very simple organic compounds from 
 their elements ; indeed the views of chemists were much divided as to the 
 possibility of such a thing. Both Gmelin and Berzelius argued that 
 organic compounds, unlike inorganic bodies, cannot be built up from 
 their elements. Organic compounds were generally believed to be special 
 products of the so-called vital force, and it was only intuitive minds, like 
 those of Liebig and Wohler, who foresaw what was coming, and wrote in 
 1837 strongly against this view, asserting that the artificial production in 
 our laboratories of all organic substances, so far as they do not constitute 
 a living organism, is not only probable but certain. Indeed, they went a 
 step farther, and predicted that sugar, morphia, salicine, will all thus be 
 prepared ; a prophecy which, I need scarcely remind you, has been after 
 fifty years fulfilled, for at the present time we can prepare an artificial 
 sweetening principle, an artificial alkaloid, and salicine. 
 
 In spite of these predictions, and in spite of Wohler's memorable 
 discovery in 1828 of the artificial production of urea, which did in 
 reality break down for ever the barrier of essential chemical difierence be- 
 tween the products of the inanimate and of the animate world, still, even 
 up to a much later date, contrary opinions were held, and the synthesis of 
 urea was looked upon as the exception which proves the rule. So it came 
 to pass that for many years the artificial production of any of the more 
 complicated organic substances was believed to be impossible. Now the 
 belief in a special vital force has disappeared like the ignis fatuus, and 
 no longer lures us in the wrong direction. We know now that the same 
 laws regulate the formation of chemical compounds in both animate and 
 inanimate nature, and the chemist only asks for a knowledge of the con- 
 stitution of any definite chemical compound found in the organic world 
 in order to be able to promise to prepare it artificially. 
 
 But the progress of synthetic organic chemistry, which has of late 
 been so rapid, was made in the early days of the half-century only by 
 feeble steps and slow. Seventeen long years elapsed between Wohler's 
 discovery and the next real synthesis. This was accomplished by Kolbe> 
 who in 1845 prepared acetic acid from its elements. But then a splendid 
 harvest of results gathered in by chemists of all nations quickly followed, 
 a harvest so rich and so varied that we are apt to be overpowered by its 
 wealth, and amidst so much that is alluring and striking we may well 
 find it difficult to choose the most appropriate examples for illustrating 
 the power and the extent of modern chemical synthesis. 
 
 Next, as a contrast to our picture, let us for a moment glance back 
 again to the state of things fifty years ago, and then notice the chief steps 
 by which we have arrived at our present position. In 1837 organic 
 chemistry possessed no scientific basis, and therefore no classification of a 
 
18 REPORT— 1887. 
 
 character worthy of the name. Writing to Berzelius in that year, Wohler 
 describes the condition of organic chemistry as one enough to drive a man 
 mad. ' It seems to me,' says he, ' like the tropical forest primeeval, full of 
 the strangest growths, an endless and pathless thicket in which a man 
 may well dread to wander.' Still clearances had already been made in 
 this wilderness of facts. Berzelius in 1832 welcomed the results of Liebig 
 and Wohler's research on benzoic acid as the dawn of anew era ; and such 
 it really was, inasmuch as it introduced a novel and fruitful idea, namely 
 the possibility of a group of atoms acting like an element by pointing out 
 the existence of organic radicals. This theory was strengthened and con- 
 firmed by Bunsen's classical researches on the cacodyl compounds, in 
 which he showed that a common group of elements which acts exactly as 
 a metal can exist in the free state, and this was followed soon afterwards 
 by isolation of the so-called alcohol radicals by Frankland and Kolbe. It 
 is, however, to Schorlemmer that we owe our knowledge of the true con- 
 stitution of these bodies, a matter which proved to be of vital importance 
 for the further development of the science. 
 
 Turning our glance in another direction we find that Dumas, in 1834,. 
 by his law of substitution threw light upon a whole series of singular 
 and unexplained phenomena by showing that an exchange can take place 
 between the constituent atoms in a molecule. Laurent indeed went 
 farther, and assumed that a chlorine atom, for example, took up the posi- 
 tion vacated by an atom of hydrogen and played the part of its displaced 
 rival, so that the chemical and physical properties of the substitution - 
 product were thought to remain substantially the same as those of the 
 original body. A singular story is connected with this discovery. At a 
 soiree in the Tuileries in the time of Charles X. the guests were almost 
 sufibcated by acrid vapours which were evidently emitted by the burning 
 wax candles, and the great chemist Dumas was called in to examine into 
 the cause of the annoyance. He found that the wax of which the candles 
 were made had been bleached by chlorine, that a replacement of some of 
 the hydrogen atoms of the wax by chlorine had occurred, and that the 
 suffocating vapours consisted of hydrochloric acid given off during the 
 combustion. The wax was as white and as odourless as before, and the 
 fact of the substitution of chlorine for hydrogen could only be recognised 
 when the candles were destroyed by burning. This incident induced 
 Dumas to investigate more closely this class of phenomena, and the re- 
 sults of this investigation are embodied in his law of substitution. So 
 far indeed did the interest of the French school of chemists lead them that 
 some assumed that not only the hydrogen but also the carbon of organic 
 bodies could be replaced by substitution. Against this idea Liebig 
 protested, and in a satirical vein he informs the chemical public, 
 writing from Paris under the nom de plume of S. Windier, that he has 
 succeeded in substituting not only the hydrogen but the oxygen and 
 carbon in cotton cloth by chlorine, and he adds that the London shops 
 are now selling nightcaps and other articles of apparel made entirely 
 
ADDRESS. 19 
 
 of chlorine, goods which meet with much favour, especially for hospital 
 
 use I 
 
 But the debt which chemistry, both inorganic and organic, thus owes 
 to Dumas' law of substitution is serious enough, for it proved to be 
 the germ of Williamson's classical researches on etherefication, as well as 
 of those of Wurtz and Hofmann on the compound ammonias, investi- 
 gations which lie at the base of the structure of modern chemistry. 
 Its influence has been, however, still more far-reaching, inasmuch as 
 upon it depends in great measure the astounding progress made in the 
 wide field of organic synthesis. 
 
 It may here be permitted to me to sketch in rough outline the prin- 
 ciples upon which all organic syntheses have been effected. We have 
 already seen that as soon as the chemical structure of a body has been 
 ascertained its artificial preparation may be certainly anticipated, so 
 that the first step to be taken is the study of the structure of the 
 naturally occurring substance which it is desired to prepare artificially 
 by resolving it into simpler constituents, the constitution of which is 
 already known. In this way, for example, Hofmann discovered that the 
 alkaloid coneine, the poisonous principle of hemlock, may be decomposed 
 into a simpler substance well known to chemists under the name of 
 pyridine. This fact having been established by Hofmann, and the 
 grouping of the atoms approximately determined, it was then necessary 
 to reverse the process, and, starting with pyridine, to build up a com- 
 pound of the required constitution and properties, a result recently 
 achieved by Ladenburg in a series of brilliant researches. The well- 
 known synthesis of the colouring matter of madder by Graebe and 
 Liebermann, preceded by the important researches of Schunck, and that 
 of indigo by Baeyer, are other striking examples in which this method has 
 been successfully followed. 
 
 Not only has this intimate acquaintance with the changes which 
 occur within the molecules of organic compounds been utilised, as we 
 have seen, in the synthesis of naturally occurring substances, but it has 
 also led to the discovery of many new ones. Of these perhaps the 
 most remarkable instance is the production of an artificial sweetening 
 agent termed saccharin, 250 times sweeter than sugar, prepared by a 
 complicated series of reactions from coal-tar. Nor must we imagine 
 that these discoveries are of scientific interest only, for they have given 
 rise to the industry of the coal-tar colours, the value of which is measured 
 by millions sterling annually, an industry which Englishmen may be 
 proud to remember was founded by our countryman Perkin. 
 
 Another interesting application of synthetic chemistry to the needs 
 of everyday life is the discovery of a series of valuable febrifuges, 
 amongst which I may mention antipyrin as the most useful. An im- 
 portant aspect in connection with the study of these bodies is the 
 physiological value which has been found to attach to the introduction 
 of certain organic radicals, so that an indication is given of the possibility 
 
20 EEPOKT— 1887. 
 
 of preparing a compound which will possess certain desired physiological 
 properties, or even to foretell the kind of action which such bodies may- 
 exert on the animal economy. 
 
 But it is not only the physiological properties of chemical compounds 
 which stand in intimate relation with their constitution, for we find that 
 this is the case with all their physical properties. It is true that at the 
 beginning of our period any such relation was almost unsuspected, whilst 
 at the present time the number of instances in which this connection has 
 been ascertained is almost infinite. Amongst these perhaps the most 
 striking is the relationship which has been pointed out between the 
 optical properties and chemical composition. This was in the first place 
 recognised by Pasteur in his classical researches on racemic and tartaric 
 acids in 1848 ; but the first to indicate a quantitative relationship and a 
 connection between chemical structure and optical properties was Glad- 
 stone in 1863. Great instrumental precision has been brought to bear on 
 this question, and consequently most important practical applications 
 have resulted. I need only refer to the well-known accurate methods 
 now in everyday use for the determination of sugar by the polariscope, 
 equally valuable to the physician and to the manufacturer. 
 
 But now the question may well be put, is any limit set to this 
 synthetic power of the chemist ? Although the danger of dogmatising 
 as to the progress of science has already been shown in too many in- 
 stances, yet one cannot help feeling that the barrier which exists between 
 the organised and unorganised worlds is one which the chemist at pre- 
 sent sees no chance of breaking down. 
 
 It is true that there are those who profess to foresee that the day 
 will arrive when the chemist, by a succession of constructive efforts, may 
 pass beyond albumen, and gather the elements of lifeless matter into 
 a living structure. Whatever may be said regarding this from other 
 standpoints, the chemist can only say that at present no such problem lies 
 within his province. Protoplasm, with which the simplest manifestations 
 of life are associated, is not a compound, but a structure built up of com- 
 pounds. The chemist may successfully synthesise any of its component 
 molecules, but he has no more reason to look forward to the synthetic 
 production of the structure than to imagine that the synthesis of gallic 
 acid leads to the artificial production of gall-nuts. 
 
 Although there is thus no prospect of our efiecfcing a synthesis of 
 organised material, yet the progress made in our knowledge of the 
 chemistry of life during the last fifty years has been very great, and so 
 much so indeed that the sciences of physiological and of pathological 
 chemistry may be said to have entirely arisen within this period. 
 
 In the introductory portion of this address I have already referred 
 to the relations supposed to exist fifty years ago between vital phenomena 
 and those of the inorganic world. Let me now briefly trace a few of 
 the more important steps which have marked the progress of this branch 
 of science during this period. Certainly no portion of our science is of 
 
ADDRESS. 2 1 
 
 greater interest, nor, I may add, of greater complexity, than that which, 
 bearing on the vital functions both of plants and of animals, endeavours 
 to unravel the tangled skein of the chemistry of life, and to explain the 
 principles according to which our bodies live, and move, and have their 
 being. If, therefore, in the less complicated problems with which other 
 portions of our science have to deal, we find ourselves, as we have seen, 
 often far from possessing satisfactoiy solutions, we cannot be surprised to 
 learn that with regard to the chemistry of the living body — whether 
 vegetable or animal — in health or disease we are still farther from a 
 complete knowledge of phenomena, even those of fundamental importance. 
 
 It is of interest here to recall the fact that nearly fifty years ago 
 Liebig presented to the Chemical Section of this Association a com- 
 mnnication in which, for the first time, an attempt was made to explain 
 the phenomena of life on chemical and physical lines, for in this paper he 
 admits the applicability of the great principle of the conservation of 
 energy to the functions of animals, pointing out that the animal cannot 
 generate more heat than is produced by the combustion of the carbon 
 and hydrogen of his food. 
 
 *The source of animal heat,' says Liebig, * has previously been 
 ascribed to nervous action or to the contraction of the muscles, or even 
 to the mechanical motions of the body, as if these motions could exist 
 without an expenditure of force [equal to that] consumed in producing 
 them.' Again he compares the living body to a laboratory furnace in 
 which a complicated series of changes occur in the fuel, but in which the 
 end-products are carbonic acid and water, the amount of heat evolved 
 being dependent, not upon the intermediate, but upon the final products. 
 Liebig asked himself the question, does every kind of food go to the 
 production of heat ; or can we distinguish, on the one hand, between the 
 kind of food which goes to create warmth, and, on the other, that by 
 the oxidation of which the motions and mechanical energy of the body 
 are kept up ? He thought that he was able to do this, and he divided 
 food into two categories ; the starchy or carbohydrate food is that, said 
 he, which by its combustion provides the warmth necessary for the 
 existence and life of the body. The albuminous or nitrogenous constituents 
 of our food, the flesh meat, the gluten, the casein out of which our 
 muscles are built up, are not available for the purposes of creating 
 warmth, but it is by the waste of those muscles that the mechanical 
 energy, the activity, the motions of the animal are supplied. We see, 
 said Liebig, that the Esquimaux feeds on fat and tallow, and this 
 burning in his body keeps out the cold. The Gaucho, riding on the 
 pampas, lives entirely on dried meat, and the rowing man and pugilist, 
 trained on beefsteaks and porter, require little food to keep up the tem- 
 perature of their bodies, but much to enable them to meet the demand 
 for fresh muscular tissue, and for this purpose they need to live on a 
 strongly nitrogenous diet. 
 
 Thus far Liebig. Now let us turn to the present state of our know- 
 
22 REPORT— 1887. 
 
 ledge. The question of the source of muscular power is one of the greatest 
 interest, for, as Frankland observes, it is the corner-stone of the physio- 
 logical edifice and the key to the nutrition of animals. 
 
 Let us examine by the light of modern science the truth of Liebig's 
 view — even now not uncommonly held — as to the functions of the two 
 kinds of food, and as to the cause of muscular exercise being the oxida- 
 tion of the muscular tissue. Soon after the promulgation of these views, 
 J. R. Mayer, whose name as the first expositor of the idea of the con- 
 servation of energy is so well known, warmly attacked them, throwing 
 out the hypothesis that all muscular action is due to the combustion of 
 food, and not to the destruction of muscle, proving his case by showing 
 that if the muscles of the heart be destroyed in doing mechanical work 
 the heart would be burnt up in eight days ! What does modern research 
 say to this question ? Can it be brought to the crucial test of experi- 
 ment ? It can ; but how ? Well, in the first place we can ascertain the 
 work done by a man or any other animal ; we can measure this work in 
 terms of our mechanical standard, in kilogramme-metres or foot-pounds. 
 We can next determine what is the destruction of nitrogenous tissue at 
 rest and under exercise by the amount of nitrogenous material thrown off 
 by the body. And here we must remember that these tissues are never 
 completely burut, so that free nitrogen is never eliminated. If now we 
 know the heat- value of the burnt muscle, it is easy to convert this into its 
 mechanical equivalent, and thus measure the energy generated. What is 
 the result ? Is the weight of muscle destroyed by ascending- the Faulhoin 
 or by working on the treadmill sufficient to produce on combustion heat 
 enough when transformed into mechanical exercise to lift the body up to 
 the summit of the Faulhorn or to do the work on the treadmill ? Careful 
 experiment has shown that this is so far from being the case that the 
 actual energy developed is twice as great as that which could possibly be 
 produced by the oxidation of the nitrogenous constituents eliminated 
 from the body during twenty-four hours. That is to say, taking the 
 amount of nitrogenous substance cast ofi" from the body, not only whilst 
 the work was being done but during twenty-four hours, the mechanical 
 effect capable of being produced by the muscular tissue from which this 
 cast-off material is derived would only raise the body halfway up the 
 Faulhorn, or enable the prisoner to work half his time on the treadmill. 
 
 Hence it is clear that Liebig's proposition is not true. The nitro- 
 genous constituents of the food do doubtless go to repair the waste of 
 muscle, which, like every other portion of the body, needs renewal, whilst 
 the function of the non-nitrogenous food is not only to supply the animal 
 heat, but also to furnish, by its oxidation, the muscular energy of the 
 body. 
 
 We thus come to the conclusion that it is the potential energy of the 
 food which furnishes the actual energy of the body, expressed in terms 
 either of heat or of mechanical work. 
 
 But there is one other factor which comes into play in this question 
 
ADDRESS. 23 
 
 of mechanical energy, and must be taken into account ; and this factor we 
 are as yet unable to estimate in our usual terms. It concerns the action 
 of the mind upon the body, and, although incapable of exact expression, 
 exerts none the less an important influence on the physics and chemistry 
 of the body, so that a connection undoubtedly exists between intellectual 
 activity or mental work and bodily nutrition. In proof that there is a 
 marked difference between voluntary and involuntary work, we need only 
 compare the mechanical action of the heart, which never causes fatigue, 
 with that of the voluntary muscles, which become fatigued by continued 
 exertion. So, too, we know well that an amount of drill which is fatiguing 
 to the recruit is not felt by the old soldier, who goes through the evolutions 
 automatically. What is the expenditure of mechanical energy which accom- 
 panies mental effort, is a question which science is probably far removed 
 from answering. But that the body experiences exhaustion as the result 
 of mental activity is a well-recognised fact. Indeed, whilst the second law 
 of thermodynamics teaches that in none of the mechanical contrivances 
 for the conversion of heat into actual energy can such a conversion be 
 complete, it is perhaps possible, as Helmholtz has suggested, that such a 
 complete conversion may take place in the subtle mechanism of the 
 animal organism. 
 
 The phenomena of vegetation, no less than those of the animal world, 
 have, however, during the last fifty years been placed by the chemist on 
 an entirely new basis. Although before the publication of Liebig's cele- 
 brated report on chemistry and its application to agriculture, presented 
 to the British Association in 1840, much had been done, many funda- 
 mental facts had been established, still Liebig's report marks an era in 
 the progress of this branch of our science. He not only gathered up in a 
 masterly fashion the results of previous workers, but put forward his own 
 original views with a boldness and frequently with a sagacity which gave 
 a vast stimulus and interest to the questions at issue. As a proof of this 
 I may remind you of the attack which he made on, and the complete 
 victory which he gained over, the humus theory. Although Saussure and 
 others had already done much to destroy the basis of this theory, yet the 
 fact remained that vegetable physiologists up to 1840 continued to hold 
 to the opinion that humus, or decayed vegetable matter, was the only 
 source of the carbon of vegetation. Liebig, giving due consideration to 
 the labours of Saussure, came to the conclusion that it was absolutely im- 
 possible that the carbon deposited as vegetable tissue over a given area, 
 as for instance over an area of forest land, could be derived from humus, 
 which is itself the result of the decay of vegetable matter. He asserted 
 that the whole of the carbon of vegetation is obtained from the atmospheric 
 carbonic acid, which, though only present in the small relative proportion 
 of 4 parts in 10,000 of air, is contained in such absolutely large quantity 
 that if all the vegetation on the earth's surface were burnt, the proportion 
 of carbonic acid which would thus be thrown into the air would not be 
 sufficient to double the present amount. 
 
24 REPORT — 1887. 
 
 That this conclusion of Liebig's is correct needed experimental proof, 
 but such proof could only be given by long-continued and laborious experi- 
 ment, and this serves to show that chemical research is not now confined 
 to laboratory experiments lasting perhaps a few minutes, but that it has 
 invaded the domain of agriculture as well as of physiology, and reckons 
 the periods of her observations in the field not by minutes, but by years. 
 It is to our English agricultural chemists Lawes and Gilbert that we 
 owe the complete experimental proof required. And it is true that this 
 experiment was a long and tedious one, for it has taken forty-four years 
 to give the definite reply. At Rothamsted a plot was set apart for the 
 growth of wheat. For forty-four successive years that field has grown 
 wheat without addition of any carbonised manure ; so that the only 
 possible source from which the plant could obtain the carbon for its 
 growth is the atmospheric carbonic acid. Now, the quantity of carbon 
 which on an average was removed in the form of wheat and straw from 
 a plot manured only with mineral matter was 1,000 pounds, whilst on 
 another plot, for which a nitrogenous manure was employed, 1,500 
 pounds more carbon was annually removed ; or 2,500 pounds of carbon 
 are removed by this crop annually without the addition of any carbona- 
 ceous manure. So that Liebig's prevision has received a complete ex- 
 perimental verification. 
 
 May I, without wearying you with experimental details, refer for a 
 moment to Liebig's views as to the assimilation of nitrogen by plants — ■ 
 a much more complicated and difficult question than the one we have 
 just considered — and compare these with the most modern results of 
 agricultural chemistry ? We find that in this case his views have not 
 been substantiated. He imagined that the whole of the nitrogen required 
 by the plant was derived from atmospheric ammonia ; whereas Lawes 
 and Gilbert have shown by experiments of a similar nature to those just 
 described, and extending over a nearly equal length of time, that this 
 source is wholly insufficient to account for the nitrogen removed in the 
 crop, and have come to the conclusion that the nitrogen must have been 
 obtained either from a store of nitrogenous material in the soil or by 
 absorption of free nitrogen from the air. These two apparently contra- 
 dictory alternatives may perhaps be reconciled by the recent observations 
 of Warrington and of Berthelot, which have thrown light upon the 
 changes which the so-called nitrogenous capital of the soil undergoes, as 
 well as upon its chemical nature, for the latter has shown that under cer- 
 tain conditions the soil has the power of absorbing the nitrogen of 
 the air, forming compounds which can subsequently be assimilated by the 
 plant. 
 
 Touching us as human beings even still more closely than the fore- 
 going, is the influence which chemistry has exerted on the science of 
 pathology, and in no direction has greater progress been made than in 
 the study of micro-organisms in relation to health and disease. In the 
 complicated chemical changes to which we give the names of fermentation 
 
ADDRESS. 25 
 
 and putrefaction, the views of Liebig, according to which these pheno- 
 mena are of a purely chemical character, have given way under the 
 searching investigations of Pasteur, who established the fundamental 
 principle that these processes are inseparably connected with the life of 
 certain low forms of organisms. Thus was founded the science of bacte- 
 riology which in Lister's hands has yielded such splendid results in the 
 treatment of surgical cases ; and in those of Klebs, Koch, and others, 
 has been the means of detecting the cause of many diseases both in man 
 and animals ; the latest and not the least important of which is the re- 
 markable series of successfal researches by Pasteur into the nature and 
 mode of cure of that most dreadful of maladies, hydrophobia. And here 
 I may be allowed to refer with satisfaction to the results of the labours on 
 this subject of a committee, the formation of which I had the honour of 
 moving for in the House of Commons. These results confirm in every 
 respect Pasteur's assertions, and prove beyond a doubt that the adoption 
 of his method has prevented the occurrence of hydrophobia in a large 
 proportion of persons bitten by rabid animals, who, if they had not been 
 subjected to this treatment would have died of that disease. The value 
 of his discovery is, however, greater than can be estimated by its present 
 utility, for it shows that it may be possible to avert other diseases besides 
 hydrophobia by the adoption of a somewhat similar method of investiga- 
 tion and of treatment. This, though the last, is certainly not the least 
 of the debts which humanity owes to the great French experimentalist. 
 Here it might seem as if we had outstepped the boundaries of chemistry, 
 and have to do with phenomena purely vital. But recent research indi- 
 cates that this is not the case, and points to the conclusion that the 
 microscopist must again give way to the chemist, and that it is by chemical 
 rather than by biological investigation that the causes of diseases will be 
 discovered, and the power of removing them obtained. For we learn 
 that the symptoms of infective diseases are no more due to the microbes 
 which constitute the infection than alcoholic intoxication is produced by 
 the yeast- cell, but that these symptoms are due to the presence of definite 
 chemical compounds, the result of the life of these microscopic organisms. 
 So it is to the action of these poisonous substances formed during the 
 life of the organism, rather than to that of the organism itself, that the 
 special characteristics of the disease are to be traced ; for it has been 
 shown that the disease can be communicated by such poisons in entire 
 absence of living organisms. 
 
 If I have thus far dwelt on the progress made in certain branches of 
 pure science it is not because I undervalue the other methods by which 
 the advancement of science is accomplished, viz., that of the application 
 and of the diffusion of a knowledge of nature, but rather because the 
 British Association has always held, and wisely held, that original investi- 
 gation lies at the root of all application, so that to foster its growth and 
 encourage its development has for more than fifty years been our chief 
 aim and wish. 
 
26 EEPORT— 1887. 
 
 Had time permitted I should have wished to have illustrated this de- 
 pendence of industrial success upon original investigation, and to have 
 pointed out the prodigious strides which chemical industry in this country 
 has made during the fifty years of her Majesty's reign. As it is I must 
 be content to remind you how much our modern life, both in its artistic 
 and useful aspects, owes to chemistry, and, therefore, how essential a 
 knowledge of the principles of the science is to all who have the industrial 
 progress of the country at heart;. 
 
 This leads me to refer to what has been accomplished in this country 
 of ours towards the diffusion of scientific knowledge amongst the people 
 during the Victorian era. It is true that the English people do not 
 possess, as yet, that appreciation of the value of science so characteristic 
 of some other nations. Up to very recent years our educational system, 
 handed down to us from the middle ages, has systematically ignored 
 science, and we are only just beginning, thanks in a great degree to the 
 prevision of the late Prince Consort, to give it a place, and that but 
 an unimportant one, in our primary and secondary schools or in our 
 universities. The country is, however, now awakening to the necessity 
 of placing its house in order in this respect, and is beginning to see that 
 if she is to maintain her commercial and industrial supremacy the 
 education of her people from top to bottom must be carried out on new 
 lines. The question as to how this can be most safely and surely ac- 
 complished is one of transcendent national importance, and the statesman 
 who solves this educational problem will earn the gratitude of generations 
 yet to come. 
 
 In conclusion, may I be allowed to welcome the unprecedentedly large 
 number of foreign men of science who have on this occasion honoured the 
 British Association by their presence, and to express the hope that this 
 meeting may be the commencement of an international scientific organi- 
 sation, the only means nowadays existing, to use the words of one of the 
 most distinguished of our guests, of establishing that fraternity among 
 nations from wh ch politics appear to remove us further and further by 
 absorbing human powers and human work, and directing them to pur- 
 poses of destruction. It would indeed be well if Great Britain, which 
 has hitherto taken the lead in so many things that are great and good, 
 should now direct her attention to the furthering of international organi- 
 sations of a scientific nature. A more appropriate occasion than the 
 present meeting could perhaps hardly be found for the inauguration of 
 such a movement. 
 
 But whether this hope be realised or not, we all unite in that one 
 great object, the search after truth for its own sake, and we all, there- 
 fore, may join in re-echoing the words of Lessing : 'The worth of man 
 lies not in the truth which he possesses, or believes that he possesses, 
 but in the honest endeavour which he puts forth to secure that truth ; 
 for not by the possession of truth, but by the search after it are the 
 faculties of man enlarged, and in this alone consists his ever-growing 
 
ADDRESS. 27 i 
 
 perfection. Possession fosters content, indolence, and pride. If God -j 
 
 should hold in His right hand all truth, and in His left hand the ever- j 
 
 active desire to seek truth, though with the condition of perpetual error, J 
 
 I would humbly ask for the contents of the left hand, saying, " Father, j 
 
 give me this ; pure truth is only for Thee." ' ] 
 
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