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 A R G E N T O N—A R G o N The city and province of Buenos Ayres have been rapidly are returned out of the total number of 116 for the whole recovering by natural causes the political predominance Republic. The chief political question agitating the people of which they lost in 1880. Representation in the Argentine Congress is accorded to the various provinces in proportion Argentina is that of heavy protective duties as against a to their population. Until 1895 the number of seats in moderate tariff—practically, protection versus free trade. the Chamber of Deputies was based upon the census of The farmers of all classes, agricultural and pastoral, 1869, which gave the provinces a large majority over the demand a reduction of the tariff; while the manucity and province of Buenos Ayres. Under the census of facturers of sugar and other articles, which thrive only 1895 the increase of population in Buenos Ayres entitled in consequence of the prohibitive duties, use all their polithe capital and province to a greater number of seats, and tical influence to maintain the existing system. (c. E. A.) no fewer than 47 members for city and province together 620

Argenton, a town of France, in the arrondissement of Chateauroux, department of Indre, on the R. Creuse, 18 miles S.S.W. of Chateauroux on the railway to Le Blanc. Excellent wine is produced; tanning, the manufacture of boots and shoes, and linen goods, are leading industries. The actual site of the ancient Argentomagus lies a little to the north, and is occupied by St Marcel. Population (1881), 5167; (1891), 5503; (1901), 6281, (comm.) 5978. Argon.—For more than a hundred years before 1894 it had been supposed that the composition of the atmosphere was thoroughly known. Beyond variable quantities of moisture and traces of carbonic acid, hydrogen, ammonia, &c., the only constituents recognized were nitrogen and oxygen. The analysis of air was conducted by determining the amount of oxygen present and assuming the remainder to be nitrogen. Since the time of Cavendish no one seemed even to have asked the question whether the residue was, in truth, all capable of conversion into nitric acid. The manner in which this condition of complacent ignorance came to be disturbed, is instructive. Observations undertaken mainly in the interest of Prout’s law, and extending over many years, had been conducted to determine afresh the densities of the principal gases—hydrogen, oxygen, and nitrogen. In the latter case, the first preparations were according to the convenient method devised by Vernon Harcourt, in which air charged with ammonia is passed over red-hot copper. Under the influence of the heat the atmospheric oxygen unites with the hydrogen of the ammonia, and when the excess of the latter is removed with sulphuric acid, the gas properly desiccated should be pure nitrogen, derived in part from the ammonia, but principally from the air. A few concordant determinations of density having been effected, the question was at first regarded as disposed of, until the thought occurred that it might be desirable to try also the more usual method of preparation in which the oxygen is removed by actual oxidation of copper without the aid of ammonia. Determinations made thus were equally concordant among themselves, but the resulting density was about ToVo Par^ greater than that found by Harcourt’s method (Rayleigh, Nature, vol. xlvi. p. 512, 1892). Subsequently when oxygen was substituted for air in the first method, so that all (instead of about one-seventh part) of the nitrogen was derived from ammonia, the difference rose to one-half per cent. • Further experiment only brought out more clearly the diversity of the gases hitherto assumed to be identical. Whatever were the means employed to rid air of accompanying oxygen, a uniform value of the density was arrived at, and this value was one-half per cent, greater than that appertaining to nitrogen extracted from compounds such as nitrous oxide, ammonia, and ammonium nitrite. No impurity, consisting of any known substance, could be discovered capable of explaining an excessive weight in the one case, or a deficiency in the other. Storage for eight months did not disturb the density of

the chemically extracted gas, nor had the silent electric discharge any influence upon either quality. (“ On an Anomaly encountered in determining the Density of Nitrogen Gas,” Proe. Boy. Soc., April 1894.) At this stage it became clear that the complication depended upon some hitherto unknown body, and probability inclined to the existence of a gas in the atmosphere heavier than nitrogen, and remaining unacted upon during the removal of the oxygen—a conclusion afterwards fully established by Rayleigh and Ramsay. The question which now pressed was as to the character of the evidence for the universally accepted view that the so-called nitrogen of the atmosphere was all of one kind, that the nitrogen of the air was the same as the nitrogen of nitre. Reference to Cavendish showed that he had already raised this question in the most distinct manner, and indeed, to a certain extent, resolved it. In his memoir of 1788 he writes :— As far as the experiments hitherto published extend, we scarcely know more of the phlogisticated part of our atmosphere than that it is not diminished by lime-water, caustic alkalies, or nitrous air ; that it is unfit to support fire or maintain life in animals ; and that its specific gravity is not much less than that of common air ; so that, though the nitrous acid, by being united to phlogiston, is converted into air possessed of these properties, and consequently, though it was reasonable to suppose, that part at least of the phlogisticated air of the atmosphere consists of this acid united to phlogiston, yet it may fairly be doubted whether the whole is of this kind, or whether there are not in reality many different substances confounded together by us under the name of phlogisticated air. I therefore made an experiment to determine whether the whole of a given portion of the phlogisticated air of the atmosphere could be reduced to nitrous acid, or w hether there was not a part of a different nature to the rest which would refuse to undergo that change. The foregoing experiments indeed, in some measure, decided this point, as much the greatest part of air let up into the tube lost its elasticity ; yet, as some remained unabsorbed, it did not appear for certain w hether that was of the same nature as the rest or not. For this purpose I diminished a similar mixture of dephlogisticated [oxygen] and common air, in the same manner as before [by sparks over alkali], till it was reduced to a small part of its original bulk. I then, in order to decompound as much as I could of the phlogisticated air [nitrogen] which remained in the tube, added some dephlogisticated air to it and continued the spark until no further diminution took place. Having by these means condensed as much as I could of the phlogisticated air, I let up some solution of liver of sulphur to absorb the dephlogisticated air ; after which only a small bubble of air remained unabsorbed, which certainly was not more than tU of the bulk of the dephlogisticated air let up into the tube ; so that, if there be any part of the dephlogisticated air of our atmosphere which differs from the rest, and cannot be reduced to nitrous acid, we may safely conclude thatitis not more than r%Ty part of the whole. Although, as was natural, Cavendish was satisfied with his result, and does not decide whether the small residue was genuine, it is probable that his residue was really of a different kind from the main bulk of the “ phlogisticated air,” and contained the gas afterwards named Argon. The announcement to the British Association in 1894 by Rayleigh and Ramsay of a new gas in the atmosphere was received with a good deal of scepticism. Some doubted the discovery of a new gas altogether, while others denied that it was present in the atmosphere. Yet there was