But these physical properties tell us nothing about what argon is, and all attempts to unveil its chemical nature have hitherto failed. Even Moissan, with his powerful electric furnace, could not overpower its inertness. Neither fluorine, which is one of the most active elements, nor titanium, boron, and lithium, which readily combine with nitrogen, could be induced to combine with argon. Berthelot alone, using the silent electrical discharge, has achieved a partial success: he made argon combine with benzine and obtained a yellow resinous substance; but the quantity of argon he had re

some red-hot magnesium or lithium,1 | Fahr. below zero, and into a block of until, most of it having combined with opaque ice at 310° below zero.2 the metal, a small quantity of argon is obtained, which yet is never quite free from nitrogen. Or else atmospheric air mixed with some oxygen is sent through a tube in which electric sparks are passed, and while the nitrogen of the air is thus induced to combine with oxygen, argon remains; but this operation, too, must be continued for hours, and the produce is never pure. There is, finally, a third method, namely, to send air through a porous membrane which separates gases of different densities, but nothing is gained by it in rapidity. All this is of course most wearisome, and even has been made a reproach to Lord Rayleigh and Pro-ceived from Professor Ramsay was so fessor Ramsay; but chemical bodies small (a little over two cubic inches) must be taken as they are, and those that nothing could be said about the of them which, like argon, refuse to produce of combination beyond its yield to chemical routine are perhaps being similar in aspect to the products the most conducive to an extension of of combination of nitrogen with benchemical knowledge. zine. Negative properties is thus all Whenever a new body is discovered, we know about the chemical nature of its leading physical properties are al-argon. Even the spectroscope this ways the easiest, and therefore the precious reconnoitring instrument — is first, to be determined. We thus know undecided in its indications. about argon that it is a colorless and spectrum of argon is quite characterinodorous gas, having about twenty istic. No other known gas or vapor, times (19.7 to 19.9) the density of Mr. Crookes writes, gives a similar hydrogen, and much more soluble in spectrum. But when a glass tube filled water than either oxygen or nitrogen. with argon is made to glow under the Accordingly, the air which is dissolved electrical discharge, and the glow is in water contains a larger proportion of examined with the spectroscope, two -one of them argon than free atmospheric air; in different spectra appear unboiled water we drink a greater pro- chiefly in the red and the other chiefly portion of dissolved argon than we in the blue-according to the energy inhale of it while breathing, and this of the discharge. These two spectra property may prove of great impor-may of course indicate that argon is a tance for vegetation if argon enters, as mixture of two gases, although it is it probably does, into the composition known that nitrogen and other gases of plants. It requires also a very low The corresponding temperatures for nitrogen are -318° and -353° Fahr. As to oxygen, it has temperature for liquefaction. Olszewski, the Cracow professor, whose ad-not yet been brought into a solid state, but it mirable achievements in the liquefaction of gases have lately been rendered popular in this country by Professor Dewar, has turned some argon which was sent to him by Professor Ramsay into a liquid at a temperature of 305°

1 This last, the lithium method, has been experimented upon with success at Nancy, by Guntz (Comptes Rendus, April 8, 1895, vol. cxx., p. 777).

The

liquefies at -297°. The critical temperature for argon is -186° Fahr., and the critical pressure amounts to 50-6 atmospheres.

3 From a subsequent communication of Ber

thelot we learn that another sample of argon, also prepared by Mr. Ramsay, behaved quite differently from the former. Eighty per cent. of the former combined with benzine, but only six to ten per

cent. of the second would enter into the same combination (Comptes Rendus, April 16, 1895, tome cxx., p. 798). Did the former contain so much nitrogen?

also show two spectra under similar even would give an additional symconditions; but Olszewski has found metry to the system. Moreover, Dr. that argon has such a definite temper- Gladstone in this country and Mr. Hill ature of liquefaction, as well as such a in America have simultaneously indidefinite critical temperature and press-cated in connection with argon a strikure, that, if it be a mixture, the ing analogy in the growth of the masses mixture must contain but a small pro- of many elements which increase alterportion of another gas. It must also nately by one unit and by three units; be borne in mind that, under our pres- and a body having an atomic weight of ent knowledge of the spectral analysis, 20 would further confirm this symit remains but an auxiliary to the metry; while Lecoq de Boisbaudran, chemist; it offers one of the means of who also has elaborated a system of preliminary exploration, but any posi- classification of elements, requires in tive decision rests with the regular his turn a body having an atomic chemical analysis. weight of a little over 20, and very inert, to fill up a gap in his system.1 All these analogies are of course very interesting; but in the mean time we have no reason to maintain that argon really is the required element; the more so as another hypothesis seems to be much more, or, at least, equally probable.

What, then, is argon, or, at least, the gas which prevails in what science already names argon? From all that has been said it does not appear probable that it is a chemical compound. A compound could hardly have resisted so many chemical and electrical tests. It has, on the contrary, all the behavior of an element; and in such case what is, then, the weight of its atom? In other words, taking the weight of an hydrogen atom for a unit, what is the corresponding weight for argon? Its density being twenty times the density of hydrogen, we know that its molécule must weigh forty times as much as an atom of hydrogen; but for argon, as for each new body whose compounds are not yet known, the difficulty is to decide how many atoms its molecule contains. If it were built on the same pattern as the molecules of hydrogen, or oxygen and many other gases, each of which consists of two atoms locked together, there would be no difficulty. We should say that its atomic weight is 20 (twenty times the weight of an hydrogen atom), and argon would find a vacant place in the row of elements between fluorine (atomic weight, 19) and sodium (23), although it must be said that its inertness would badly clash in this case with the chemical properties of its next-door neighbors. In the Mendeléeff periodic classification of elements it would also find a ready place, and

1 For critical temperatures and pressures see a previous" Recent Science" review (LIVING AGE, No. 2602).

All hitherto obtained argon was contaminated by nitrogen, which is lighter than argon. Consequently we cannot be sure that its density is exactly 19.9; it may exceed 20, and even approach to 21, in which case its molecular weight would be about 42; and then argon, in all probability, would be nothing but an allotropic form of nitrogen. We know indeed that the atmosphere contains a varying proportion of ozone, which is nothing but a condensed form of oxygen grouped in molecules of three atoms each (0 ̧), while the molecule of common oxygen contains only two atoms (O2). It is therefore possible that nitrogen, too, might appear in two forms: with a triatomic molecule (N,) in argon, and with the usual biatomic molecule (N2) in ordinary nitrogen. This is the hypothesis towards which Mendeléeff, Berthelot, and Professor Dewar incline, and various circumstances yield it a

2 By giving an eighth group (or column) to the second series, which is an "even" series - several other even series also having their eighth groups -and by having certain properties characteristic of the eighth groups or columns.

3 J. H. Gladstone's letter in Nature, February 21, 1895; and E. E. Hill's "Argon, Prout's Hypothesis, and the Periodic Law" in American Journal of Science, May, 1895, p. 405.

▲ Comptes Rendus, 1895, tome cxx., p. 361.

II.

certain support, namely, the concurrent appearance of argon and nitrogen THE researches were at this point in in nature, the difficulty of separating March last, when another far-reaching them from each other, their inertness, discovery was announced by Professor exaggerated in argon, their common Ramsay. It being known that most lines in the spectra, their double metals and minerals absorb various spectra themselves, and the outer gases which can be extracted from the resemblance between their benzine metal or mineral, it was natural to incompounds in Berthelot's experiments; quire whether some minerals might not perhaps also the fact that a small contain argon. This was done, and in quantity of argon was found in nitro- the course of his investigations Progen obtained from one of its com- fessor Ramsay was brought to extract pounds.1 and to analyze the gas which is conHowever, certain measurements rela-tained in a lately discovered mineral, tive to the heat-absorbing capacity of clevéite, and which was said to be argon-too technical to be discussed in nitrogen. This gas contained a revelathis place seem to point out that, tion. It proved to be argon, as Mr. under our present conceptions as to the Ramsay expected, but argon mixed arrangement of atoms in molecules, we with some other gas; and this gas, on ought to consider the molecule of argon spectroscopic examination, displayed, (like the molecule of mercury vapors) among very many other lines, one as consisting of one atom only. In bright yellow line which at once caught this case the weights of both its mole- the attention of the explorers. It was cule and its atom would be equal to 40. not the well-known yellow line of But not only is there no room for such sodium, but was identified by Mr. a body in the periodical system - the Crookes as another line frequently seen place being already occupied - but in the spectrum of the sun's chromoargon would stand by its chemical sphere, but never obtained before from inertness as a unique exception in any terrestrial object. This line, being a classification which indicates the very characteristic of the gases of the chemical properties of every other ele- sun's atmosphere, was ascribed several ment from its position in the system. years ago to some element unknown The periodic law will certainly not be on the earth, but widely spread on thrown overboard to suit this unique the sun, which was therefore named exception; so that chemists and physi- helium. Now, this element was finally cists may perhaps have to revise their captured in a glass tube in the laborapresent ideas as to the arrangement of tory.3 atoms in molecules, and to complete One can easily imagine the sensation them by introducing into molecular produced by the announcement of this structure the conception of chemical discovery. Many chemists had for energy. Who knows whether the contradiction displayed by argon will not be an impulse to the appearance of some epoch-making work on the structure of matter? 2

years searched for helium among the substances which exist on the earth and in meteorites fallen from the celestial spaces, but in vain; while now the longed-for yellow line glittered in the spectroscope, quite unexpectedly, 1 Lord Rayleigh and Mr. Ramsay explain this originating from a by-produce discovlast circumstance by the fact that in the manipu-ered in the search for argon! Upon the reception of the welcome news, the Upsala Professor Cleve (in whose

lation of the gases large quantities of water were used, and water freely dissolves argon; to which Mendeléeff very justly remarks that this is undoubtedly very possible, but has to be proved. See Lord Rayleigh's objections to this hypothesis in his Royal Institution lecture (Nature, June 13, 1895).

It is well worth noticing that the case of argon is opposed to the case of chlorine, which is chemically a most active body, and also deviates from

the law, but in an opposite direction. (See Mendeléeff's note on argon, l.c.)

3 Communication made to the Chemical Society at its anniversary meeting (Nature, April 4, 1895, vol. li., p. 543, lii., p. 7; Proceedings of the Royal Society, April 25).

usually found in atmospheric argon, and which may be the cause of the high density of the latter. Three or four distinct gases have thus been discovered - or rather preliminarily pointed out by the spectroscope while several more are already in view.

We thus stand on the threshold of most important discoveries which are sure to throw much light on the chemical processes going on on the surfaces of the celestial bodies, and certainly will endow the physics of the sun and the stars with important generalizations; while on the other side the discovery of one or perhaps two gases, possessed of low atomic weights, which have hitherto been vainly sought for, will undoubtedly free our chemical classification from an incertitude which

honor Nordenskjöld had named the learned from Professor Ramsay that, mineral) at once extracted the new while boiling clevéite in weak sulgases, and Thalén, one of the best phuric acid, he obtained not only the spectroscopists of our time, fully con- gas supposed to be helium, but also firmed Mr. Crookes's statement. The argon devoid of some gas which is gas obtained at Upsala showed the same yellow line, but it contained no trace of argon; and Cleve at once ascertained that it was of a very low density. This was confirmed by subsequent experiments, and the last news from Upsala is to the effect that Cleve's helium has only 2-02 times the density of hydrogen, so that its atomic weight must be either four or two. The Upsala gas would thus come into the wide gap existing in our lists of elements between hydrogen, whose atomic weight is taken for a unit, and lithium, whose atom is seven times heavier than the atom of hydrogen.1 On the other side, Mr. Lockyer has obtained the new gas by another method, from another mineral of the same group, bröggerite; it was associated with hydrogen, but, like Cleve's gas, contained no argon. The same has prevailed till now. And, finally, brilliant yellow line of helium shines in the theoretical questions arising from the spectrum of the bröggerite gas, in company with several other lines which were known in the spectrum of the sun's chromosphere, but had never been seen before in the spectra of terrestrial objects.2 It appears, moreover, from a second and third communication of Mr. Lockyer to the Royal Society that he has found traces of other solar gases mixed with helium, and that he expects to obtain by his method quite a series of gases, the spectral lines of which are associated with the spectral lines of the chromosphere. At the same date we

3

1 Mr. Ramsay has found that his gas (obtained from a mixture with argon) has a density of 3.89, and the same monatomic structure as argon, or at least the same ratio of specific heats.

2 Proceedings of the Royal Society, April 25, 1895; Nature, May 2, 1895, vol. lii., p. 8.

3 Nature, May 10, 1895, vol. lii., p. 56.

The fact of several chromosphere lines being seen at the same time is the more important, as Professor C. Runge, armed with one of the best spectroscopes, maintains (in a letter dated May 16, and published in Nature, June 6, 1895) that the yellow line obtained from clevéite is not at all the helium line, but consists of two lines situated on both sides of the latter. Up to this date (June 19)

the properties of argon, and even from the very errors which may have been made during the earlier hypothetical period of discussion, are sure to launch physics and chemistry in a new domain of philosophical speculation. This mass of discoveries, rapidly following each other, may seem bewildering; but they were not unexpected. For years chemistry had cautiously perfected its methods, and minutely accumulated new data in a limited circle of facts.

Now, the fruits of that laborious work are rapidly ripening. "Are we facing a new period in chemistry?" Cleve exclaimed at the end of a letter in which he announced his discovery. Undoubtedly we are entering a period when both our knowledge of facts and our theoretical views in chemistry will be immensely widened.

the contradiction between such authorities in spectroscopy as Runge, Crookes, Lockyer, and Thalén has not been explained in the press; but the concurrent appearance of several chromospheric lines leaves little doubt as to discovery of gases which prevail in the atmosphere of the sun.

III.

a subject of controversy for the last seventy years; but it is only now that our ideas upon the whole subject begin to take a definite shape.

A few years ago, two Austrian

tending to study the distribution of electricity in the atmosphere at different heights, inaugurated a series of

We live in an atmosphere which is loaded with electricity. When heavy storm-clouds obscure the sky, and, taking those yellowish tints which are characteristic of electrified vapors, meteorologists, Elster and Geitel, insend towards the earth immense sparks of lightning, the electricity in the atmosphere becomes visible. We may also collect it in the way Franklin and simultaneous measurements, at the Buffon used to collect it, by means of observatory which is planted on the kites launched high in the air, and top of the Sonnblick (a high peak of study it in the laboratory. Again, the Tyrolean Alps), and in a valley at when cold weather sets in over the dry the foot of the peak. They had, howplateaus of Siberia or America, the air ever, to realize to their regret that becomes so permeated with electricity their comparative measurements were that a fur coat, thrown off in the a failure, because a waterfall which obscurity, glitters with crepitating runs in the valley so much electrified sparks. But even in cloudless weather the air around it, up to an altitude of in western Europe, if the naturalist sixteen hundred feet, that no compariwalks about with a portable electrom- son was possible between the low-level eter, and measures the density of and the high-level observations. This electricity in the air, as Lord Kelvin unsuccess brought the question as to did many years ago, when he repeated the electrifying powers of waterfalls Pouillet's experiments on the sea- again to the front, and Herr Lenard beach of the Island of Arran, the con-undertook a series of observations on tinual changes in the instrument's their electrical effects in Switzerland.1 indications will show that masses of It appeared that, to say nothing of highly electrified air are continually large waterfalls, even the small ones, wafted along by the gentle breezes at a certain height, and thus transport and distribute electricity in the atmosphere. And, finally, the electrometers which have been installed at many observatories - partly with the hope that their indications would be of some help in the prediction of local storms and rains show that at every moment of the day the charge of electricity contained in the atmosphere is changing, so that even at two spots situated near to each other the indications of the instruments may vary in the most capricious way.

That the electricity which we find in the atmosphere may originate from various sources-from the evaporation of water which is continually going on on the earth's surface, from the unequal heating of superposed strata of air, from vegetation, and even from chemical changes which go on on the surface of the earth was pointed out long since; and the relative importance of these different causes has remained

a few feet high, send into the air considerable charges of electricity, provided they bring down a large amount of rapidly dashing water. The smallest jets of water, which drip on the rock sides, and even roaring streamlets, have the same effect; while above the surfaces of quiet lakes no electrification of the air was detected, notwithstanding the constantly going on of evaporation. In further prosecuting his researches, Lenard came to the conclusion that the current theory which explains electrification in the neighborhood of waterfalls by the inductive action of the positive electricity which is usually spread in the air during fine weather, is not supported by observation. He also remarked that neither evaporation nor the mere rushing of water drops through the air would explain the phenomena, and that the chief cause of electrification of the air is the tearing asunder of the drops of 1 Wiedemann's Annalen der Physik, 1892, Bd. xlvi., p. 584 8q.