CHEMICAL NEWS, Jan. 30, 1891.

THE

VOL. LXIII. No. 1627.

the reason why they have had no influence on the development of chemical science.

THE TELLURIC SCREW.

MANY of our readers will have felt surprised by the recent announcement that MM, Lecoq de Boisbaudran and A. de Lapparent have discovered a new claimant for priority in the recognition of the Periodic Law. Their surprise will not be lessened when they see the memoir which was read on the 12th instant, and which we reproduce textually. The chemist who is said to have anticipated Mr. J. Newlands, and a fortiori Professor Mendeleeff and Professor Lothar Meyer, in announcing the periodic arrangement of the simple bodies is M. Béguyer de Chancourtois. His researches, made known in 1862, have not been disinterred from some forgotten "pli cacheté," or found in the back numbers of some obscure journal. They are to be seen in the Comptes Rendus! Hence, MM. de Boisbaudran and Lapparent seek to know how these documents can have escaped the attention of Mr. Newlands? To answer one question by another we must ask how they can have escaped the notice of M. de Boisbaudran and his friend for a term of nearly twenty-nine years to be at last suddenly sprung upon the world?

The Periodic Law, it must be remembered, when first announced was not immediately accepted. When Mr. Newlands read his memoir before the Chemical Society (March, 1886), it by no means met with a very enthusiastic reception. One gentleman present even inquired, sarcastically, whether the author "had ever arranged the elements according to the order of their initial letters?" but no one suggested any anticipation.

Then came the announcement by Professors Mendeleeff and L. Meyer of their independent and simultaneous discovery of the same truth. The details were quickly circulated and discussed in the scientific press, and the respective merit of the two savants was for a time a bone of contention. Professor Mendeleeff said (CHEMICAL NEWS, vol. xliii., page 15):-"It is possible that Newlands has, prior to me, enunciated something similar to the Periodic Law, but even this cannot be said of L. Meyer." Yet none of all the authorities who criticised or applauded the new discovery suggests that Newlands, Mendeleeff, and Meyer might all have been anticipated. When M. Lecoq de Boisbaudran made his discovery of gallium he seemed not gratified at the assertion that its existence and its properties had been foreseen in accordance with the Periodic Law. But he made no reference to the "Telluric Screw."

When the successful attempt was made to vindicate the claims of Newlands as the first discoverer, the question was thoroughly re-discussed. But none of the savants who entered into the question ever breathed the name of De Chancourtois. His memoirs were at all times accessible in the Comptes Rendus. But no one found in them that meaning which MM. de Boisbaudran and de Lapparent now assert. They certainly contain a proposal to classify the elements with reference to their atomic weights. But we may be permitted to doubt whether they can be fairly considered as the germ of the Periodic Law.

In going over old researches we often find in them matter which we may now regard as a forecast of subse. quent discoveries; but there is no sufficient evidence that the author disentangled such matter from accompanying speculations. In the third paragraph from the end of the memoir which we have translated, we find an admission that such has been the case with the writings of M. de Chancourtois, Were his writings placed

A RECLAMATION OF PRIORITY ON BEHALF
OF M. DE CHANCOURTOIS REFERRING
TO THE NUMERICAL RELATIONS OF
THE ATOMIC WEIGHTS.

By MM. LECOQ DE BOISBAUDRAN and A. DE LAPPARent
IN 1884 Mr. John Newlands collected under the following
title, "On the Discovery of the Law of Periodicity, and
on Relations among the Atomic Weights," a number of
memoirs which he had previously published in the
CHEMICAL NEWS during the years 1864, 1865, and 1866.
The object of the publication was to claim on behalf
of Mr. Newlands the priority of the announcement of
certain numerical relations which exist among the atomic
weights, and which enable us to group the simple bodies
in natural families. The author took care to establish
that his researches had preceded those of Professor
Mendeleeff, and he affirms that he was the first to publish
(on July 30th, 1864), a list of all the elements known
arranged in the order of their atomic weights.
It is not our intention to contest the merit of the well-
known works of Mr. Newlands. Our object is merely to
establish that the priority in this matter does not belong
to him, as several of the ideas which he believes he was
the first to announce in 1864 had been formulated two
years previously by a French savant before the Academy
of Sciences.

On April 7th, 1862, Béguyer de Chancourtois, at that time Chief Engineer and Assistant Professor of Geology at the School of Mines, presented to the Academy a work entitled: "On a Natural Classification of the Simple or Radicle Bodies entitled The Telluric Screw." In two subsequent communications (April 21st and May 5th, 1862), the author furnished supplementary details. On October 13th of the same year, he presented to the Academy a lithographic table which summed up all his ideas. Finally, on March 16th, 1863, he concluded with certain general considerations on the numerical character of the simple bodies, as well as on the verifications which spectral analysis might furnish. In this paper is found the very explicit assertion that "the properties of bodies are properties of numbers."

The fundamental idea of the "telluric screw " consists in writing the values of the atomic weights along the generatrix of a vertical cylinder, the circular base of which was divided into 16 equal parts, 16 being the atomic weight of oxygen. If we then trace upon this cylinder a helix with an angle of 45 to its axis, each point of the helix may be considered as the characteristic point of a simple body, the atomic weight of which to the proportional corresponding length of the spiral will be read upon the generatrix which passes by this point.

At each turn the helix returns on one and the same perpendicular at distances from the summit of the cylinder, which are entire multiples of 16, and mark the bodies whose atomic weights conform to this condition. In the same manner the various points of intersection of the helix with any of the 16 principal generatrices, correspond to elements whose atomic weights differ among themselves by 16 or a multiple of 16. Lastly, if after having developed the cylinder upon a plane which transforms the helix into a series of straight parallel segments, we join by a straight line any two points taken upon two segments, after coiling up this right line will produce a secondary helix, and the intersections of this latter with the various turns of the principal helix will mark bodies for which the differences of the atomic weights will be

multiples of a constant quantity. In this manner, the development of the "telluric screw" by simply drawing right lines enables us to show simple numerical relations which it would have been less easy to detect by a mere inspection of the figures.

The relations thus established among the atomic weights correspond for the most part to real analogies in the properties of the corresponding elements. This Chancourtois affirmed in his first memoir, asserting that the "relations of the properties of bodies are manifested by simple relations of position of their characteristic points; and then that each of the helices carried through two characteristic points, and passing by several other points, or merely in their proximity, shows relations of properties of a certain kind, the analogies or the contrasts being manifested by certain numerical orders of succession like the immediate sequence or the alternations at diverse periods.

The "telluric screw" shows at once a classification of the elements according to the order of their atomic weights and the indication of a true periodicity. This is exactly what Mr. Newlands has claimed as especially belonging to him. It is not up to the comparison of atomic periodicity with the musical gamut, of which we cannot deny that it has been, if not proclaimed, at least "interviewed" by Chancourtois. For in his paper of May 5th, 1862, he says expressly: "We cannot refrain from remarking the predominance of the number 7 in the types of the groups occupying the spirals which are most occupied..... We arrive easily at the idea of transforming the cylinder upon which the screw is realised into a sonorous tube pierced at the characteristic points." But especially when he published in 1863 a pamphlet containing, along with his memoirs to the Academy some additions which the plan of the Comptes Rendus had not allowed him to give in extenso. Chancourtois spoke of "direct developments of the system which enable us to perceive at the same time approximations of the series of numerical characteristics to the series of musical sounds, and to that of the bands and rays of the spectrum."

We are far from pretending that the theory of the screw is free from faults, and that the author has not grafted upon his work many considerations which he had better had left in the shade. Several approximations were inaccurate or were strained, and some of them evince a too great part allowed to the imagination. Confiding too much in the virtue of whole numbers (and even of primary numbers), Chancourtois set out with the idea that in the natural series the differences between the atomic weights ought to be constant (an error which, indeed, is also to be met with in the earliest researches of Newlands). If he, indeed, recognised certain gaps in the series of the elements, he endeavoured to fill them up by imagining new varieties of the known simple bodies (which he called secondary characters), and which often led him to arrangements little conformable to natural analogies.

Nevertheless, the "telluric screw" was, for its time, an original and even a fruitful conception, for it sufficed to let the author conjecture that the formula of zirconia should probably be written ZrO2, that of beryllia BeO, and that of yttria Yt203. Further, nothing but the consideration of his helix could have suggested to Chancourtois the slight correction which it was proper to make in the atomic weight of cadmium.

NEWS

columns which should be joined end to end), a reduction of that part of the graphic table which extends from hydrogen to tellurium. The secondary helix has been traced which passes by sulphur, iron, selenium, tellurium, and which, if produced, would extend to gold.-Comptes Rendus, vol. cxiij., p. 77.

A NATIONAL CHEMICAL SOCIETY IN AMERICA.

THE second general meeting of the American Chemical Society was held in the University of Pennsylvania, at Philadelphia, December 30th and 31st, 1890. Professor GEORGE F. Barker, M.D., President. The attendance was large, the arrangements for both business and for entertainment were excellent, and many valuable papers were read which will be published in the Journal.

Under the auspices of the American Chemical Society a conference of chemists, representing seven different bodies, assembled to consider the formation of a National Organisation of American Chemists. The societies or bodies represented by delegates were the following:(1) Chemical Section of the American Association for the Advancement of Science. (2) American Chemical Society. (3) Chemical Section of the Franklin Institute, Philadelphia. (4) Chemical Section of the Brooklyn Institute. (5) Association of Official Agricultural Chemists. (6) Chemical Society of Washington, D.C. (7) Manufacturing Chemists' Association of the United States. The newly formed Chemical Society of Cincin. nati was not represented.

Professor Albert B. Prescott, of Ann Arbor, Michigan, President-Elect of the American Association for the Advancement of Science, was called to the chair, and Dr. H. Carrington Bolton, of New York, was appointed Secretary.

After a prolonged and interesting discussion the following resolutions were adopted.

Resolution 1.-It is desirable that an American Association of Chemists be formed to embrace all existing American Chemical organisations.

Resolution 2.-Resolved, That this conference recommend to all existing American Chemical organisations that they call a meeting of their bodies to be held in Washington, D.C., in connection with the meeting of the American Association for the Advancement of Science for 1891, and that each of these organisations be requested to appoint a committee, or to continue their present committee for the further discussion of the subject submitted to the conference now in session.

Resolution 3.-Resolved, That this general conference committee, composed of the present sub-committees, or such others as may be appointed by the several organisations, be called together at as early a time as practicable before the joint meeting recommended in Resolution 2.

Resolution 4.-Resolved, That meanwhile, each subcommittee through its chairman, by correspondence or otherwise, shall formulate such modifications of the Constitution of the American Chemical Society as it shall deem necessary to adapt it to the requirements of the Association proposed.

Resolution 5.-Resolved, That the chairmen of these sub-committees shall then, so far as possible, harmonise the views embodied in these reports of their several organisations, and shall have printed, for presentation at the joint meeting, a report, or minority and majority reports, on a constitution for the proposed Association of American Chemists.

ELECTRICITY

IN TRANSITU:

FROM PLENUM TO VACUUM.*

By WILLIAM CROOKES, F.R.S., President of the Institution of Electrical Engineers.

Introduction.

WHILST steadily bearing in mind that I have the honour to address a Society, not only of physicists, but of Electrical Engineers, I shall not, I hope, be out of order in venturing to call your attention to a purely abstract phase of Electrical Science. Numberless instances show that pure research is the abundant source from which spring endless streams of practical applications. We all know how speculative inquiry into the influence of electricity on the nervous system of animals led to knowledge of current electricity, and ultimately to the priceless possession of the telegraph and the telephone. The abstract study of certain microscopic forms of parasitic vegetable life has enabled us to give to fermented solutions of sugar the exact flavour and aroma of the most highly prized wines, and probably, ere long, will put us in a position to increase at will the fertility of the soil. In a different direction the same class of abstract researches applied to medical science has brought us within measurable distance of the final conquest over a large class of diseases hitherto incurable; and without egotism I may, perhaps, be allowed to say that my own researches into high vacua to some extent have contributed to the present degree of perfection of the incandescence lamp. Surely, therefore, whilst eagerly reaping and storing the harvest of practical benefits, we must not neglect to scatter more seed for future results, perchance not less wonderful and valuable.

In another respect I deviate to some extent from the course taken by many of my predecessors. I am about to treat electricity, not so much as an end in itself, but rather as a tool, by whose judicious use we may gain some addition to our scanty knowledge of the atoms and molecules of matter and of the forms of energy which by their mutual reactions constitute the universe as it is manifest to our five senses.

I will endeavour to explain what I mean by characterising electricity as a tool. When working as a chemist in the laboratory, I find the induction spark often of great service in discriminating one element from another, also in indicating the presence of hitherto unknown elements in other bodies in quantity far too minute to be recognisable by any other means. In this way, chemists have discovered thallium, gallium, germanium, and numerous other elements. On the other hand, when examining electrical reactions in high vacua, various rare chemical elements become in turn tests for recognising the intensity and character of electric energy. Electricity, positive and negative, effect respectively different movements and luminosities. Hence the behaviour of the substances upon which electricity acts may indicate with which of these two kinds we have to deal. In other physical researches both electricity and chemistry come into play simply as means of exploration.

In submitting to you certain researches in which elec. tricity is used as a tool, or as a means of bringing within scope of our senses phenomena that otherwise would be unrevealed, I must for a moment recal to your minds the now generally accepted theory of the constitution of

matter.

creature pushes against a piece of gravel or directs its course between the interstices. To the worm, therefore, gravel seems by no means homogeneous and continuous.

With speculations as to the constitution of liquid and solid matter I need not trouble you, but will proceed at once to the third or gaseous state of matter.

The kinetic theory of gases teaches that the constituent molecules dart in every possible direction with great but continually varying velocities, coming almost ceaselessly in mutual collision with each other. The distance each molecule traverses without hitting another molecule is known as its free path; the average distance traversed without collision by the whole number of molecules of a gas at any given pressure and temperature is called the mean free path. The molecules exert pressure in all directions, and are only restrained by gravitation from dissipating themselves into space. In ordinary gases, the length of the mean free path of the molecules is exceedingly small compared with the dimensions of the vessel, and the properties we then observe are such as constitute the ordinary gaseous state of matter, which depend upon constant collisions. But if we greatly reduce the number of molecules in a given extent of space the free path of the molecules under electric impulse is so long that the number of their mutual collisions in any given time in comparsion with the number of times they fail to collide may be disregarded. Hence, the average molecule can carry out its own motions without interference. When the mean free path becomes comparable to the dimensions of the containing vessel, the attributes which constitute gaseity shrink to a minimum, the matter attains the ultra-gaseous or "radiant ” state, and we arrive at a con. dition where molecular motions under electrical impulse can easily be studied.

The mean free path of the molecules of a gas increases so rapidly with progressive exhaustion, that whilst that of the molecules of air at the ordinary pressure is only 1-10,000th of a millimetre, at an exhaustion of a hundredmillionth of an atmosphere-a point (which, with present appliances, is easy to attain) corresponding to the rarefac tion of the air 90 miles above the earth's surface-the mean free path will be about 30 feet; whilst at 200 miles above the earth it will be 10,000,000 miles, and millions of miles out in the depth of space it will become practically infinite. I could go on speculating in spite of Aristotle, who said:-" Beyond the universe there are neither space, nor vacuum, nor time."

In discussing the motions of molecules we have to dis tinguish the free path from the mean free path. Nothing is yet known of the absolute length of the free path nor of the absolute velocity of a molecule. For anything we can prove to the contrary, these values may vary almost from zero to infinity. We can deal only with the mean free path and the mean velocity.

The Vacuum Pump.

As most of the experiments I put before you to-night are connected with high vacua, it is not out of place to refer to the pump by means of which these tubes are exhausted. Much has been said lately in recommendation of the Geissler pump and its many improvements, but I am still strongly in favour of the Sprengel, as with it I have obtained greater exhaustion than with any other. I should like to point out that the action does not stop when we cease to see air specks passing down the tubes but continues long after this point has been passed. Neither is the non-conducting vacuum, so easily obtained by the Sprengel pump, due in any way to the presence of mercury vapour, since non-conduction can be obtained just as rapidly when special precautions have been taken to keep mercury vapour out of the tubes.

One of the great advantages of the Sprengel pump over all others lies in the fact that its internal capacity need not exceed a few cubic centimetres, and there is, therefore much less wall surface for gases to condense upon. I have brought the very latest modification of this form

of pump here to-night, and you will have an opportunity of seeing it in action and of measuring with the McLeod gauge the rarefaction it produces.*

My measurements of high vacua have all been taken with the beautiful little gauge devised by Professor McLeod. Unmerited discredit has recently been cast on this gauge, the principal fault alleged being its inability to distinguish between the tension of the permanent gas and that of the mercury vapour present. Now it is evident that, under ordinary circumstances, the tension of mercury vapour may be disregarded, as it will be the same on both sides of the gauge; and it will be only in cases where no mercury is present on one side of the gauge that a slight error is introduced. It is, however, very difficult to devise and successfully experiment with apparatus in which a trace of mercury vapour shall not enter, and it is not

NEWS

The Passage of Electricity Through Rarefied Gas. The various phenomena presented when an induction spark is made to pass through a gas at different degrees of exhaustion point to a modified condition of the matter at the highest exhaustions. Here are three exaaly similar bulbs, the electrodes being aluminium balls, and the internal pressures being respectively 75 m.m., 2 m.m., and o'i m.m. If I pass the induction current in succession through the bulbs, you will perceive in each case a very different luminous phenomena. Here is a slightly exhausted tube (Fig. 1), like the first in the series just exhibited (75 m.m.), the induction spark passes from one

FIG. 2.-P. likely that an experimentalist who would be working with such mercury-free apparatus would attempt to use the gauge without remembering that in this special case the indications would be incorrect. To use the McLeod gauge requires much patience and some amount of experience, but I have always found it trustworthy to register exhaustions far beyond the millionth of an atmosphere. I can adduce circumstantial evidence of the accuracy of its readings at these high vacua. In the year 1881 I read a paper before the Royal Society on "The Viscosity of Gases at High Exhaustions" (Phil. Trans., 1881, 387), and illustrated my results in three large diagrams, on which I plotted the experimental results obtained at rarefactions up to 0.02 millionth of an atmosphere, giving curves comparing the decrease in viscosity with that of the repulsion resulting from radiation, at the different pressures. Now these curves, in the case of air for instance, are perfectly regular and uniform in their falling off, and it is evi dent that this could not have been the case unless the ordinates

o'i m.m.

end to the other, A, B, and the luminous discharge is seen as a line of light, acting as a flexible conductor. Under the tube I have an electro-magnet, c, and on making conrepresenting viscosity and the abscissæ representing pressure were equally accurate. I am satisfied that, within narrow limits, the ordinates of viscosity are correct to the highest point, and the conformity of experiment to theory in the shape of these curves is a conclusive proof that, at as high an exhaustion as o'02 M., the McLeod gauge is to be trusted to give accurate results within 2 per cent of the truth. To give some idea what these high exhaustions mean I may mention that the highest measured exhaustion-o'oz M.-bears the same proportion to the ordinary pressure of the atmosphere that a millimetre does to 30 miles, or in point of time, that one second bears to 20 months.