of the total sulphur. The extreme variation in our own TINCTORIAL CHEMISTRY, ANCIENT AND By Prof. RAPHAEL MELDOLA, F.R.S. IN giving place to my successor in the Presidential Chair of the Society of Dyers and Colourists, I should like to take advantage of the present opportunity of offering some general considerations concerning the functions of such technical organisations as that over which, by your courtesy, it has been my privilege to preside since the lamented death of our former President, Sir William Perkin. The subject which it is the business of this Society to foster and promote is both an art and a science. As an art it is, as you are all aware, one of extreme antiquity; as a science its development is comparatively modern, for while the dyers and colourists of what may be called the pre-Perkin period were perforce compelled to use natural colouring matters, the modern dyeing or printing establish ment is now practically dependent upon the synthetical products derived from coal-tar. The substitution of synthetical for natural dyes has naturally entailed great modification in the mode of application, and tinctorial operations as now conducted are, or at any rate should be, no longer treated as an empirical handicraft, but as a scientific art based upon a sure foundation—the knowledge of the physical and chemical properties of the materials supplied to tinctorial industry by chemical manufacturers. "Rule-of-thumb" fumbling with recipes and prescriptions with a limited number of vegetable dye-stuffs of fluctuating shade and variable strength, and often unknown chemical composition, has been superseded by the introduction of hundreds of definite chemical compounds of constant shade and unvarying tinctorial power. In brief, we are enabled now to deal with products of which the colour, strength, fastness, &c., are inherent properties as definite for each individual compound as are the properties of a triangle or of any other geometrical figure. The art has become approximated towards an exact science. Such a revolution in an industry of venerable antiquity as has been effected in about half a century has, perhaps, never before been witnessed in the history of applied science. Scientific discovery has, it is true, called new branches of industry into existence, and has thus opened up new fields of human enterprise and outlets for capital and labour. But in our case there has been no new creation; an ancient industry at the touch of science has become transformed. asked to what cause or causes this rapid development is due, there can be only one answer-the development of the science of Organic Chemistry. From the time of Perkin's discovery of mauve in 1856, down to the very latest patents for new dye-stuffs, it has been science and nothing but science all along the line. And by science let it be understood that we do not mean only the discovery of new compounds, but the determination of chemical constitution, and the search after general theoretical principles connecting colour and other properties with chemical constitution. If this be fully realised it will be seen that not the least important function of societies such as ours is the bringing together of the representatives of science and the representatives of industry. It has long been familiar to students of economics-whether we in this country recognise the doctrine or not-that industrial development is ultimately dependent upon scientific development. Fiscal considerations may have some influence in promoting or retarding an industry, but primarily the financial economist, as well as the political economist, is dependent upon the materials supplied by productive industry, and the production of these materials in the most advantageous way and the addition of new materials to the resources of civilisation is the business of scientific research, and it is therefore scientific activity which is the real and solid basis of national prosperity. The nation which fails to realise this principle is bound to go under in the long run in that industrial struggle which is certain to become keener with the progress of science and the severity of competition arising therefrom. Organisations such as this Society, which promote alliance between those who are cultivating chemistry in its scientific aspects and those whose business it is to avail themselves of the practical applications of scientific discovery, are from this point of view doing work of something more than local significance; they are helping to promulgate a principle of national importance-they are doing for this country what the scientific foresight and wisdom of the German manufacturers did for their country in the early days of the coal-tar colour industry. when the "pure" chemistry of the university laboratories associated itself with the "applied" chemistry of the factories, with results which are now only too well known. It is no detraction from the merits of the work of our Society-in fact, it should serve to stimulate loyal support for the promotion of its objects from every representative of the industry throughout the country-if 1 remind you that its functions are analogous in general principle to those of an older Continential organisation with which we are all familiar; I refer to the "Société Industrielle de Mulhouse," whose work is of international value, and whose Bulletin may, without exaggeration, be described as the model of a technical scientific journal. The Fifteen Year Period, 1870-1885, in the History of the Coal-tar Colour Industry and its Lessons. In dwelling upon the strengthening of the bonds between science and industry as one of the most important functions of this and kindred Societies, I am prompted by the thought that the realisation of the importance-the vital importance of this union has not been fully grasped in this country even at the present time. Our industry in the course of its history has furnished abundant illustration of that principle which we as a nation have not thoroughly assimilated-the direct practical bearing of science, ever. in its highest and most abstract form, upon technical and manufacturing operations. For more than a quarter of a century I have taken every opportunity of emphasising the object lesson conveyed by the history of that branch of chemical industry which immediately concerns us here; the manufacture of coal-tar products inaugurated in 1856 by my illustrious predecessor in this Chair, whose services to that industry formed the subject of my Address two years ago. Perkin himself did more than any worker of his time to inculcate that doctrine both by precept and * From the Journal of the Society of Dyers and Colourists, xxvi., No. 5. example. It is the spirit of propagandism which encourages All this is, of course, common knowledge to the members of our Society; to many I may appear to be stating a mere truism. Nevertheless, the history of the development of tinctorial art is so interwoven with general principles of fundamental importance that it may be excusable to dwell on the subject to some extent on this occasion. If it be CHEMICAL NEWS, June 10, 1910 Tinctorial Chemistry. me to belabour this somewhat jaded hobby on such an occasion as the present one, when it is my privilege to be able to appeal to a wider public through the representatives of an art that is well to the fore in the utilisation of the resources which science has placed at its disposal and through the members of a Society which may be congratulated on doing good service to that cause which we So far, however, as I am concerned, all have at heart. the preaching of the doctrine that the development of the coal tar colour industry is primarily the outcome of scientific research is nothing more than the iteration of ancient history. It is interesting to note in passing that it is considered necessary to re-state this fact from time to time with all the air of novelty (see, for the latest pronouncement, The Times "Engineering Supplement," Nov. 17th, 1909). But after all, if a principle is true, and if its truth is not generally recognised, it may be desirable to freshen up the public mind from time to time, if only for the purpose of reinforcing a lesson which is in danger of being forgotten. From the opinion recently credited to some Hungarian chemist (said to have been twenty years in an English dye-house), in the organ of the Hungarian Association of Chemical Industry (loc. cit., Feb. 9th, 1910), in which both the facts and their conclusions are distorted in a most remarkable way, it is perfectly clear that there is still scope for reiteration. Fortunately, it is possible for me to support the position which I have always maintained by an appeal to that particularly critical period in the history of the industry when I was connected with it, viz., the period following the Franco-Prussian War of 1870. It was soon after this great European disaster that the Continential manufacturers began to get seriously to work, and some ten years later we in this country and the French manufacturers experienced the first symptoms of serious competition from the introduction of new products resulting from German discoveries. Before 1870 and for a few years subsequently the list of synthetic dye-stuffs Those made at Greenford Green during Perkin's time (1857-1873) were given in a list published The staple products in my last Address to this Society. when I first entered the industry in 1870 were Magenta and the blues derived therefrom, the Hofmann Violets, the Britannia Violets of Perkin, Bismarck Brown, Manchester Yellow, Indulines, Alizarin, and Methyl Violet, the latter discovered by Lauth in 1861 and manufactured in Poirrier's A few minor products such as Phosfactory near Paris. phine, Aniline Yellow, Aldehyde Green, &c., were made by certain firms, but it is unnecessary to swell the list. good green for dyeing purposes was known, and the sowas too costly and fugitive to be called "Iodine Green At the time of my second connection with of much use. the coal-tar colour industry, which began in 1877, the old state of affairs was beginning to change-at first slowly, but with increasing velocity-and at the time of my severance in 1885, the change was progressing with such speed that I foresaw the approaching decline of our supremacy in that industry, and did my best on every possible occasion to direct public attention to the existing was a short one. state of affairs. No Now it happens that the period covered by my own personal reminiscences-say, from 1870 to 1885-was the most active in the discovery of new types of colouring matters in the whole history of the industry. I do not mean to say that no new types have been discovered since 1885, or that the actual numbers of individual dyes put on the market since that date may not have been greater than But it is the discovery of new types or before that date. of the chemical constitution of old types which is the scientific achievement which precedes and prompts the industrial development, and furnishes the manufacturer with the means of producing new compounds of tinctorial value. With the unravelling of chemical structure comes suggestions for new methods of producing compounds of certain specific types, so that the clue furnished by the determination of the constitution of one compound may lead to innumerable compounds of the same type being But its The oldest and most largely made dye-stuff in the early days of the industry was magenta or fuchsine, for the full history of which I refer you to the books. This colouring matter had been made the subject of much scientific study by many distinguished chemists, and its chemical composition and mode of formation were well known. chemical constitution was a mystery till the year 1878, when the problem was attacked by chemists armed with a new mental weapon, and therefore capable of looking at the question from a new point of view. That weapon was, of course, the Kekulé theory, which had by that time become part of the mental equipment of every truly scientific chemist, and the chemists who paved the way for the solution of this problem were Caro and Graebe, and the men who finally solved it were Emil and Otto Fischer. It is only necessary to state the bare facts here; they are all recorded in history, but I shall never forget the keen delight with which I first read those memorable papers of 18781880, in which the Fischers proved that parafuchsine and magenta were derivatives of the hydrocarbon triphenylmethane and its homologue respectively. This discovery settled a point which had engaged the attention of chemists, from Hofmann downwards, for a period of about twenty years. Turn now to the practical consequences of this purely academic piece of work. The type had been revealed. Others of the older dye-stuffs, such as the Methyl Violet of Lauth, the Hofmann Violets, the Phenylated Blues, &c., were all seen to belong to the same type. Furthermore, a well known green dye-stuff, Malachite Green, discovered by O. Fischer in 1877 and by Doebner (independently) in 1878-the first direct dyeing green of real value-and a few other greens introduced about the same time or a little later, and all made by the same processes, were proved to be derivatives of triphenyl methane. Then followed the scientific development Totally new arising naturally from the Fischers' demonstration, viz., the building up the triphenylmethane type. search, and the successful search, for other methods of methods were devised and new branches of the industry sprang into existence. aldehyde method of Fischer, we had the so-called phosgene colours, such as the Victoria Blues, Night Blue, Crystal Violet, &c., all of which appeared in 1883. In rapid succession there appeared later dyes of the same type in which I have taken the trouble of tetramethyldiaminobenzhydrol or formaldehyde played the part of condensing agents. which bring out this chapter of applied chemistry in a very compiling some lists (from Schultz's tables), the results of Before the Fischers' work, there were on the vivid way. market, roughly speaking, some 20 dyes of this class. I refer only to the basic dyes or their sulphonic acids. Many In addition to the aromatic of these older dyes were not definite compounds at all, but indefinite mixtures or residues and by-products. Now the manufacture of magenta began on the small scale in France about 1859, so that the 20 dyes (of which only some 15 can be claimed as definite products) represent a period of activity of nineteen years. From 1878 to 1891, the latest date in Schultz's tables for a colouring matter of this type (Green's Ed. of 1894), i.e., during a period of thirteen years, 24 new colouring matters of this class were introduced, everyone a definite compound, and some of them competing with and ultimately displacing some of the older dyes of the same class, which, up to that period had been the staple products upon which some of our manufacturers here had absolutely depended to keep their works going. I now turn to another large and important group of colouring matters, the discovery of which belongs to the period with which I am dealing. In 1871, Prof. v. Baeyer published the first of a series of papers on some new types of compounds which he had obtained by the condensation of phenols with phthalic anhydride, and which he termed "phthaleïns." This, as in the previous case, was at first a piece of purely scientific work. Now, fortunately for that country, Germany had in one of her new colour factories a chemist whose services we in this country had lost-a man who is happily still with us and whose name will be indelibly stamped upon the history of the develop. ment of the coal-tar colour industry. I refer to my old friend Dr. Heinrich Caro, of Mannheim. It was he who recognised the technological importance of Baeyer's work, and turned this "academic" chemical reaction into a manufacturing process by his discovery that the substituted phthaleïns were possessed of great tinctorial value. Thus appeared in 1874 the eosins, the bromo-derivatives of resorcin-phthalein, and I have a vivid recollection of the excitement with which I first experimented with some of these beautiful new dyes when, somewhat later, they first found their way to this country. The subsequent history is substantially as before. The principle that substituted phthaleïns were dye-stuffs had been discovered; further discovery for some years turned upon methods for introducing various substituents into the phthaleïns, and the list was rapidly extended. From this discovery of Baeyer's in 1871 there was thus developed another branch of industry, creating a demand for raw materials such as phthalic anhydride and resorcinol, which had never before been made on a large scale. In the meantime, Baeyer and other Continential chemists were slowly unravelling the mystery of the chemical constitution of the phthaleïns, and after some years it was shown that they were closely related in type to the triphenylmethane group. It may be of interest to add that the question of the constitution of these compounds is still under investigation, but this is a chapter of modern chemistry. The direct descendants of these earlier substituted phthaleïns are the well known rhodamines, first introduced in 1887. Another important group of colouring matters belonging to the same period owes its origin to a discovery by Lauth in 1876, viz., that certain diamines when oxidised in the presence of sulphuretted hydrogen gave rise to the formation of violet dyes. At first this also was a purely academic discovery; "Lauth's Violet" never became an important addition to the list of available dye-stuffs on account of its cost. But the same year the principle was extended by Caro, with the result that " Methylene Blue" was introduced. Here, again, I have a vivid recollection of the sensation produced in this country by the introduction of a new blue dye-stuff. Up to that period all the known blues were phenylated rosanilines. No basic blue soluble in water had ever been available for tinctorial industry. The basic phenylated rosanilines had, on account of their insolubility, to be used in alcoholic solution, and the water soluble blues were salts of sulphonic acids. The chemical constitution of Methylene Blue was attacked as a scientific problem by Bernthsen in 1883, and successfully elucidated in a masterly series of researches which bore the usual practical result. New and more advantageous methods of | making the colouring matter were discovered, and the original Methylene Blue was soon followed by a number of new dye-stuffs belonging to the same type. This same eventful period witnessed the introduction of other great groups of colouring matters. It is unnecessary to re-state at length histories which are already upon record. I need only mention Naphthol Yellow or Acid Yellow (1879), the Oxazines (1879), the Indophenols (1881), the new series of azo-colours which began with Chrysoïdine and Naphthol Orange (1875-1876), Fast Red, the Ponceaux, Bordeaux, and Biebrich Scarlet (1878-1879), Blue Black (1882), Congo Red, the first of the direct cotton dyes, and the first representative of that enormous series of azo-colours derived from tolidine, dianisidine, &c. (1884-1885). Then we had the new series of quinoline dyes beginning with Flavaniline (1881), and the renewed interest in the Safranines and allied colouring matters arising from the researches of Witt and Nietzki, and the consequent introduction of many new dye-stuffs belonging to this type beginning with Phenosafranine (1878), the "eurodines" (1879), Neutral Violet (1880), &c. Safranine, as you will remember, was first recognised among the products of oxidation of aniline (crude) by Perkin in 1861, and his own Mauve, the first of the coal-tar dyes, was in later times (1888) proved by Fischer and Hepp to be a member of this same series. Within this same period also falls the discovery of the first method of producing the "sulphide colours," which have since become of such great importance and which began, in germ, with the old "Cachou de Laval" of Croissant and Bretonière in 1873. So also there remain to be recorded the numerous and important developments in the alizarian group, beginning with Alizarin Orange (1875), Alizarin Blue (1878), Alizarin Blue S (1882), &c., Galleïn and Coeruleïn (1878), the first of the hydrazine colours, Tartrazine (1884), and Sun Yellow, the first of the stilbene dyes (1883). And last, and by no means least, we have the first indigo synthesis by Baeyer in 1880, and the second (Baeyer and Drewsen) two years later, and the settlement of the constitution of this allimportant colouring matter in 1888 by this same master worker. Chemical Research the Prime Factor in the Development of the Coal-tar Colour Industry. I have narrated this chapter of industrial chemical history in the barest outline, because the details can be filled in by reference to existing literature. But I have spoken of nothing of which I have not personal recollection, because at that period it was my regular habit to keep myself acquainted, as far as was made known through the ordinary channels of publication, with what was going on in the colour industry outside our own works, and speci. mens of the new colouring matters sooner or later found their way into our laboratory. I claim therefore with some confidence that this period of fifteen years was not only, as I have said, a most eventful one, but it may even be permissible to go further and to declare that it was the most critical period in the whole history of the coal-tar colour industry. It was the period which witnessed the introduction of nearly all the chemical types of colouring matters on the market at the present time, and it was, above all, the period which saw the stagnation and the commencement of the decay of the British coal-tar colour industry. A careful examination of the history of this period should therefore furnish lessons of the utmost importance. What does this history reveal? In the first place, the broad fact that there was immense activity in the way of discovery, and in the next place, that the centre of this activity was not in this country. Consider all these new types of colouring matters or every individual dye discovered during the period, and it will be found that our national contribution to the industry was quite insignificant as compared with the foreign and especially the German discoveries. The question of the cause of the decline of the British industry resolves in reality into the question of the cause of the Continental activity. CHEMICAL NEWS, } Alterations of Plants as a Result of Environment. The answer to this last question has been staring us broadly in the face for over thirty years. It is amazing that there should have ever been any doubt about, or any other cause suggested than the true cause, which is The foreign manufacturers knew RESEARCH-writ large! what it meant and realised its importance, and they tapped the universities and technical high schools, and they added research departments and research chemists to their factories, while our manufacturers were taking no steps at all, or were calmly hugging themselves into a state of false security, based on the belief that the old order under which they had been prosperous was imperishable. It is true that when the effects of the new discoveries began to make themselves felt, one or two factories did add a research chemist to the staff, but the number and the means of work were totally inadequate. I happened to be one of them, and so I speak with some practical knowledge We were but as a handful of light of the conditions. skirmishers against an army of trained legionaries. What could three or four-say half a dozen at a liberal estimate -research chemists, working under every disadvantage, do against scores, increasing to hundreds, of highly trained university chemists, equipped with all the facilities for research, encouraged and paid to devote their whole time to research, and backed up by technological skill of the highest order? The cause of the decline of our supremacy in this colour industry is no mystery-it is transparently and painfully obvious. In the early stages of its decadence it had little or nothing to do with faulty patent legislation The decay or excise restrictions with respect to alcohol. of the British industry set in from the time when the Continental factories allied themselves with pure science, and the British manufacturers neglected such aid, or secured it to an absurdly inadequate extent in view of the strength of the competing forces. I am It has often been asserted that the British colour industry suffered from the imperfection of our patent laws. quite prepared to admit that there is some justification for this contention; our patent laws were faulty-they are by no means perfect now-but that is a very different thing from the assertion that the imperfection of the patent laws it This I never did was the main cause of our decadence. The history of that fifteen year and never can admit. period refutes it. I say, and always have said, that it was primarily our neglect of science which was respon sible for our stagnation, in precisely the same way as may be said, per contra, that it was the appreciation of science which was the cause of the progress Had our factories been creative of our competitors. centres, as coveries of great industrial value been pouring out of research laboratories here, I cannot but believe that the pressure from within would have forced the hands of the legislature, and would have brought about an amelioration of the patent laws long ago. Instead of attributing the decline of our colour industry to the imperfection of our patent laws, the argument, as it seems to me, may fairly be inverted, and it may be said that the imperfection of our patent laws was largely due to our want of initiative in the colour industry. were the Continental factories-had dis (NOTE. In support of this view it may be mentioned that the German Patent Laws were also faulty at this period, as proved by the fact that some of the early discoveries, e.g., eosin by Caro, were not patented on account of the imperfection of the protection afforded by patents. The manufacture of the phthaleïns was carried out secretly until the new dyes came into the hands of scientific chemists. Thus Hofmann first made public the chemical constitution of eosin (Ber., 1875, p. 62), and of chrysoïdine It must be borne in mind also that (Ber., 1877, p. 213). the scientific discoveries of Baeyer, Fischer, &c., which prompted the technical developments were public property, and as freely at the disposal of English as of German manufacturers). (To be continued). PROCEEDINGS OF SOCIETIES. ROYAL SOCIETY. 273 "Alterations of the Development and Forms of Plants as a Result of Environment." By Prof. G. KLEBS, Heidelberg. (The Croonian Lecture). But The fungus Saprolegnia is chosen as an example among the lower plants. This fungus lives on dead insects, and shows three distinct stages of its development :-(1) Vegetative growth of the mycelium; (2) asexual reproduction Under ordinary conditions these three by motile zoospores; (3) sexual reproduction by male and female organs. stages follow one another quite regularly till, after the ripening of the resting spores, the fungus dies. according to the special conditions of every stage, it is Under very favourable conditions of possible to produce them as we desire, and also to alter their succession. Numerous other nutrition, the fungus must continuously grow, without being propagating and without dying. lower plants, as fungi and algæ, show the same relations to environment. Flowering-plants present far more difficulties, in consequence of their very complicated structure. Sempervivum Sempervivum appears funckii is taken to show how far the development of such a plant depends on environment. as a short stem covered with thick sappy leaves; we call this form a rosette. The rosettes produce in an asexual way new daughter-rosettes, of which each comes to flower under suitable conditions, and dies after the ripening of seeds. The state of a plant destined to flower but without recognisable rudiments, is called ripe to flower. formation of the inflorescence consists of three essential The stages: (1) The lengthening of the stem; (2) the production of several branches at the top; (3) the birth of flowers. On the other hand, the Under very favourable conditions of nutrition, a rosette one, which must always grow without sexual reproduction. ripe to flower can be transformed again into a vegetative In blue light, during March and April, a lengthening of the rosette ripe to flower takes place, but without flowering. Such a lengthening of the stem is wholly independent of flowering, because all rosettes, also the youngest ones, are able to lengthen in red light. flowers can result without lengthening, when the rosettes are exposed to a high temperature. The production of flowering branches can be prevented, the inflorescence at the end having but a single flower. branches are to be found on the whole stem, even in the We come to a new series of forms by replacing flowers axils of the old leaves, particularly as result of injuries. inflorescence, even on the flowering branches, alone or by leaf-rosettes, which can be produced on all parts of the mingled with flowers. The plants, of which the inflorescence bears rosettes, do not die at the end of summer as is normal, but live another two or more years, appearing in peculiar forms. It can be shown that flowers vary in an exceedingly high degree under certain conditions. The number and arrangement of all members as sepals, petals, stamens, and carpels can be altered. Further striking variations of the normal forms appear in such artificially modified flowers by the transformation of sepals into petals, of petals into stamens, of stamens into petals and into carpels. Experiments were made to answer the question whether alterations of flowers can be transmitted. For such researches Sempervivum acuminatum, which produces easily ripe seeds, was used. The seeds of flowers artificially altered and self-fertilised gave rise to twenty-one seedlings, among which four showed surprising deviations in their flowers. With two seedlings all the flowers were greatly altered and presented some of the alterations of the mother plant, especially the transformation of stamens into petals. The experiments are being continued. In other conditions, numerous PHYSICAL SOCIETY. Prof. H. L. CALLENDAR, F.R.S., President, in the Chair. A PAPER "On an Oscillation Detector Actuated Solely by ECCLES. The experiments described in the present paper are offered as additional support for the author's hypothesis of the mode of action of certain types of electrical oscillation detectors. This hypothesis suggests that in detectors constituted of a loose contact, the energy of the oscillatory current through the contact is transformed into heat at the contact, and warms the matter there sufficiently to change its electrical resistance, and, consequently, the steady current through the indicating instrument. The principal deductions from this hypothesis were worked out, and were illustrated by experiments on iron-oxide coherers in a paper read before the Physical Society on March 11th last. The present experiments are on a detector of the so-called "crystal rectifier" type, from which, however, the possibility of thermo-electric effects have been eliminated. This detector consists merely of a loose contact between two pieces of galena-a substance which according to the author's theory ought, by virtue of its large negative coefficient of change of resistance with temperature, to be a very efficient detector of electrical vibrations. The experimental curves obtained from a galena-galena detector are:-The steady current curve, the sensitiveness curve, and the power curve. The first has steadily applied E.M.F. as abscissæ, and current through the detector circuit as ordinates. It proves to be a curve which, in general, rises slowly at first, then quickly, and then slowly again; but if the circuit be arranged to have but little resistance other than that at the contact, the former is really the curve required for strict quantitative correlation with the experimental facts of the behaviour of the detector towards high-frequency electrical oscillations. The isothermal curves actually obtained are the same in character as the adiabatic ones, to a sufficiently close approximation. If the masses of the crystals were reduced, as Prof. Lees suggested, in order to reduce the heat-losses from the contact, then the metal leads to which the crystals are soldered might be brought near enough to the contact to make the heat-losses larger, not smaller. The chief advantage of making the crystals smaller accrues from the reduction of that idle portion of the electrical resistance of the detector, which undergoes no temperature change of the kind desired. The author practically accomplishes this already by copper-plating the crystals all over, soldering into place, and then baring the small area of crystal required for the contact. Mr. A. EAGLE exhibited a "Resonance Transformer." The transformer is practically a Rowland's coil. The capacity shunted across the secondary is so chosen that resonance is obtained with the alternating current supplied to the primary. The condition for this is where L and N are the self-inductions (L-M) Cp 1, wh of the secondary and primary respectively, M is the mutual induction between them, C is the capacity, and is 2 π times the frequency. In this way large condensers may be charged to a high potential very economically. Such a transformer forms a non-inductive load. Besides the great saving in current there is also a saving in energy due to the fact that the current from the secondary has not the tendency to flow through the spark-gap in the form of an arc-discharge as in the general case. II0 watts have sufficed to run a spark with a condenser of, m.f.d. capacity at a potential of 8500 volts (R.M.S.). The chief advantage of the resonance transformer lies in the character of the sparks. The voltage rise according to the law k V=Vm(1-e-kt) sin pt, the time constant, is over I second. Hence, if at intervals of I loge Vm curve may possess a negative gradient at the point of inflexion. The chief difficulty met in obtaining these steady-current curves arose from the slow movements of heat through the mass of the crystals-which have, of small thermal conductivity. where This difficulty was course, overcome, and the true character of the curves brought to light, by allowing a proper time-interval for thermal Vs is the sparking potential, sparks will follow each other equilibrium to be established before each galvanometerreading was taken. The sensitiveness curve has the E.M.F. applied to the detector as abscissæ, and the power passed to the indicating instrument as ordinates; the intensity of the electrical vibrations being of fixed amount. It is a curve which rises to a maximum near the point of greatest slope of the former curve, and thereafter descends slowly. The power curve has the power supplied to the detector in the form of electrical oscillations as abscissæ, with the power passed by the detector to the indicating instrument as ordinates, the steady E.M.F. applied to the detector being the best value. This curve is a straight line. The properties of this "crystal rectifier" are therefore just such as are logically deducible from the fundamental fact that the contact possesses a negative resistancetemperature coefficient. Mr. W. DUDDELL said the author was making progress with his thermal theory of coherers. He pointed out that in the experiments described considerable time was taken in determining the part of the steady current curve with negative characteristic, whereas in practice the changes were very rapid. Prof. C. H. LEES remarked that Dr. Eccles had introduced simplicity into a very difficult subject. He agreed with the remarks of Mr. Duddell, and suggested using very minute points and surfaces so that less time would be occupied in securing thermal equilibrium. The working conditions would thus be more nearly reproduced. The AUTHOR, in his reply to the remarks of Mr. Duddell and Prof. Lees, explained that in order to get a correct notion of the character of the steady current curves, the curves should be drawn either very quickly or very slowly; that is to say, either adiabatically or isothermally. The The interval can be varied within wide limits by varying Vm by altering the choking coil in the primary circuit. A succession of clear and distinct discharges is thus obtained instead of an undifferentiated stream of sparks with more or less of an arc-discharge superposed on them. A paper entitled "The Limitations of the Weston Cell as a Standard of Electromotive Force" was read by Mr. S. W. J. SMITH. In this paper the recent experiments of Mr. F. E. Smith on cadmium amalgams are discussed from the point of view of the modern theory of alloys. Theory and experiment alike suggest that there is no range at any temperature over which the E.M.F. of a Weston cell is absolutely independent of the percentage of Cd in the amalgam. Even if the materials are quite pure, the existence of surface energy must cause some variation. Within the range over which the E.M.F. is usually taken as constant the E.M.F. appears to rise very slowly, with increase in the cadmium content. The rate varies, but is never more than a few millionths of a volt for 1 per cent Cd. From the data it seems possible also to discover the precise way in which the use of the richer two phase amalgams may lead to variability of the E.M.F. of the Weston cell. The interpretation advocated is that the irregularities are due to electrolytic skin effects arising out of want of uniformity of composition of the surface grains. The probable reason why the temperature coefficient of E.M.F. of a Weston cell, always small, actually vanishes near o° C. is indicated. An outline of the way in which |