interesting process, which has been adopted by the Canadian Smelting Works at Trail, B.C. At these works there are 28 refining tanks each, 7 ft. 2 in. by 2 ft. 6 in. by 3 ft. 6 in. each, and containing 22 pairs of electrodes. The anodes The are of lead rich in precious metals, as much as 300 oz. of silver and 3 oz. of gold being present. The electrolyte is lead fluosilicate, which is prepared by running hydrofluoric acid through a tank filled with quartz, and dissolving white lead in the hydrofluorosilicic acid thus produced. The chief merit of lead fluosilicate is its great solubility, and the fact that it can be induced to yield compact deposits of lead. A plain fluosilicate solution will give tree-like growths, but if gelatine is added the lead comes down in a dense form. The rationale of this addition is as obscure as many things are in electro-chemistry. working of this method is rather akin to the refining of silver in a nitric acid solution. The more precious metals remain behind as anode sludge, and the commoner sort will dissolve and will not come down on the cathodes. In practice it is found that the silver remains with the sludge, and that the quantity of baser metals contained in the electrolyte is not excessive. With a cost of power of 6 per horse-power year, the inventor computes the expenditure on this item for refining at 2s. 8d. per ton of lead, and states that the remaining sources of outlay are not greater than those of the Parkes process. I doubt whether a proper comparison can be made in this way; there are sources of expenditure proper to both processes, and these cannot be equated en bloc; they must be dealt with separately and in detail. I have a shrewd suspicion that for some years to come lead with be reduced and refined by methods which are not electrolytic. Miscellaneous. MEMORIAL TABLETS. The London County Council, in continuation of the work which it has taken over from the Society of Arts, has placed a tablet on No. 67, Wimpole-street, the house in which Henry Hallam, the historian, lived from 1819 to 1840. The late Mr. Hutton, in his "Literary Landmarks of London," states that it was here that Hallam wrote his first great work, his "View of the State of Europe during the Middle Ages," but this is obviously incorrect, since the book was published in 1818, and it was only on his return from the Continent, whither he had gone in the summer of that year, that Hallam settled in Wimpolestreet. But the "Constitutional History of England from the Accession of Henry VII. to the Death of George II.," published in 1827, and the "Introduction to the Literature of Europe in the Fifteenth, Sixteenth, and Seventeenth Centuries," published in 1837-9, were certainly written there. Hallam was all but heart-broken before the completion of the last of these works by the sudden death of his son, Arthur Henry Hallam, immortalised by Tennyson in "In Memoriam." "I have warnings," wrote the historian at this time, “to gather my sheaves while I can—my advanced age and the reunion in heaven with those who await me," and he wrote little else after completing the book then in preparation, though he lived for another twenty-six years. More sorrows fell to his lot in Wimpole-street, for in 1837 and 1840 his daughter Ellen and his wife died. Tennyson, in "In Memoriam," thus describes the house as he knew it, when his college friend, the historian's eldest son, lived there : "Dark house, by which once more I stand, Doors, where my heart was used to beat, A hand that can be clasped no more." Arthur Hallam was only twenty-two when he died, and his literary remains, which were added to the pathetic memoir written by his father, and privately printed in 1834, showed remarkable promise; but his memory will be preserved by Tennyson's poem rather than by any of his own productions.-The Daily Graphic. THE SUGAR INDUSTRY IN SIAM. The cultivation of sugar cane in Siam, and the manufacture of sugar, are industries which are capable of being increased greatly with the introduction of better methods in the production of the cane, and modern machinery for the manufacture of the sugar. According to Consul Everard Nash, of Bangkok, the method of cultivation and manufacture which prevails at present is as follows:-Cane is planted during the dry season-December to June-to make cuttings for planting in the beginning of the rainy seasonabout the end of June. These sections of cane are then planted one or two together, the ground being kept well weeded and thoroughly hoed three or four times during growth. The ripe cane is crushed and the pieces boiled in an iron pot, with the addition of a small quantity of lime, which precipitates the impurities and enables the clear liquid to be drawn off through a pipe into a second 'pot, where it is again boiled until it becomes a pale yellow colour. This boiling operation is repeated successively in three more pots, when the syrup has reached the consistency and colour of molasses. The molasses is then ladled into small earthen pots, provided with apertures (like flower pots), closed by plugs, and then allowed to cool over night. When cold the pots are placed on other pots, the plugs removed, and the molasses allowed to drain off, leaving a coarse, yellow sugar. The process of refining consists in pressing down in the pots the coarse sugar thus produced, covering it with prepared earth, and allowing it to stand for a fortnight. Upon removing the earth, a certain part of the sugar is found to be quite white. The layer is then removed, exposing the yellow sugar underneath, when the process is repeated until all the sugar is refined. The molasses which draws into the lower pots in the course of these operations, is reboiled, and subjected to the same processes as before. The quantity of sugar manufactured is far from being sufficient for home consumption, as in 1902, sugar was imported to the value of £182,000, and raw sugar, £3,900. It will be observed from a study of the statistics of Siamese imports, that while the imports of refined sugar are increasing enormously, the unrefined product shows a marked decrease. This can be accounted for in either of two ways. The Siamese are learning to prefer refined sugar, or the production of the unrefined variety is increasing greatly. There are, unfortunately, no statistics of the amount of home-grown cane. Correspondence. HAND-WEAVING INDUSTRY OF INDIA. I shall be obliged by your giving me an opportunity of controverting the statement made in Mr. Coombes' article in your issue of 5th August, 1904, that the foot power or “domestic " loom is altogether unsuited for India. I introduced these looms with great success in the great penal settlement at Port Blair, all worked by Indian female convicts. They were an enormous improvement on the hand looms in use, and had the following advantages:-They produced a cloth of uniform quality, coarse or fine; the "lengths" produced were constant; the task of each woman could be accurately gauged and fixed according to her strength. All this was very difficult before they were introduced, as with hand looms, the quality of the weaving depends on individual skill, and the cloth produced in a factory varies therefore in quality with each weaver employed. A sharp weaver, too, with a hand loom, can much too easily "fake" the lengths, in a way not easy of detection during the weaving, by not beating up sufficiently. The quality of the cloth is thus spoilt, but the task, fixed in lengths in a given time, is eased. Our experience in a factory conducted on a scale probably not tried elsewhere-the women weave annually all the clothing required for over 10,000 convicts was that one woman, on a domestic loom, could weave as much cloth at least, in a given time, as three women on hand looms, and that, too, of an incomparably superior and uniform quality. We found, also, that the women took very readily to the new loom. There were difficulties, of course, on first introduction, but these did not last long. The chief difficulty in the general introduction of the domestic looms lies in the warp, which has to be good and of uniform quality, such as the Indian hand weaver does not usually produce, but this bad habit of his also spoils the hand-woven cloths he produces. We found special machinery necessary for producing a warp good enough for the domestic loom, but that was quite cheap and can be supplied by the same firms that supply the looms. Indeed, so favourably was I impressed with the experiment with the domestic looms, that I reported strongly in its favour to the Government of India, and had I remained in India I should have taken up the domestic loom as a machine likely to be of general use in the country, for home industries. But I now perceive that I should have met with "expert" opposition from a quarter where I should not have looked for it. I cannot help feeling disappointed that in his zeal for the hand loom, Mr. Coombes should have paid insufficient attention to the merits of the foot loon, which is a very much better machine. If such natural difficulties as are in the way of its general introduction, were resolutely faced, it would give the native weaver a chance be can never otherwise get of competing with the powerloom woven cloths. R. TEMPLE. The Nash, Worcester. August 6th, 1904. General Notes. ASSISTANT TEACHERS IN FRENCH LYCÉES.— The Board of Education have received from the French Government a notification of their intention to attach as temporary assistants to certain Lycées a number of young English secondary schoolmasters, or intending schoolmasters, who have undergone an approved course of training and hold some recognised diploma for secondary teachers. These assistants will not take any share in the regular work of the school, but will conduct small conversation groups under the direction of the Proviseur. Two hours' work a day will be expected of them. The rest of their time will be at the disposal of the assistants, who will thus be able to pursue their own studies. The assistants will receive no remuneration, but will be be boarded and lodged at the institutions to which they are attached. Candidates for such posts should forward their applications to the Director of Special Inquiries and Reports, St. Stephen's House, Cannonrow, S.W., enclosing testimonials as to character, capacity, and teaching experience, and a medical certificate of health. It will also be necessary for each candidate to have a personal interview with the Director at his office, and should any candidate have any special desire as to date of interview, it would be well to indicate it when forwarding the application. CANTOR LECTURES. RECENT ADVANCES IN ELECTRO- BY BERTRAM BLOUNT, F.I.C. Lecture II.-Delivered March 14th, 1904. PREPARATION OF METALS FROM FUSED ELECTROLYTES. Aluminium.-Aluminium affords a typical instance of a metal which is prepared exclusively by electrolysis in a fused bath. The number of attempts which have been made to prepare it in some other way would literally fill a book-they have indeed filled several. The whole history is highly instructive. Because aluminium needs for its reduction a great expenditure of energy it cannot be reduced from its oxide at any ordinary metallurgical temperature, and at the higher temperature of the electric furnace it unites with part of the carbon necessary for its reduction. Aluminium carbide, though an interesting body, is of no commercial value at present; hence electric furnace methods are not directly practicable. It is possible enough that eventually they may be applied for producing aluminium. Let us suppose alumina reduced by carbon at a very high temperature in the electric furnace, and aluminium carbide obtained. If this were fused with alumina the product should be aluminium, the reaction proceeding very much as that indicated by Moissan for chromium. Unhappily for this idea, aluminium at this great temperature would probably volatilise, and the condensation and collection of the distilled metal might prove difficult. Dismissing these speculations, let us examine the condition of the art. There is a single process for making aluminium which consists in electrolysing an aluminium salt or oxide between a carbon anode and an aluminium cathode, the bath being kept hot by the current itself. The process is named according to patents and patriotism, Hall, Héroult or Minet, but in essence it is the same. Before discussing the electrolysis of aluminium salts, it is necessary to speak of alumina. This is the raw material of aluminium, and on its abundance and purity the cheapness and quality of the metal depend. The process used by the British Aluminium Company at Larne, may be taken as a good example of the care and skill which have to be bestowed on the manufacture of this material. At Larne, the original intention was to use an Irish bauxite, which contains a high percentage of alumina, and is fairly free from iron. But in practice it was found better to use bauxite imported from France. The French mineral contains 12 to 15 per cent. of ferric oxide, but yields a better return of alumina than the Irish ore, the chief reason being that in the process of extraction the latter, with its considerable proportion of silica, formed an insoluble double silicate of alumina and soda, whereby not only is alumina lost, but soda is wasted. This unexpected result is one of those troubles, common in all new undertakings, which are extremely difficult to guard against; something might have been done by small scale working controlled by analyses of the ingoing and outcoming stuff, but even if that plan were adopted, it is by no means certain that the reactions would proceed just as they do on a large scale. Faraday once said that when he went into a works, all his chemistry dropped out at his finger-ends; probably Faraday's great modesty misled him, but for lesser people his remark is exact. It is the hardest thing to translate well-known and definite chemical reactions into manufacturing practice. At Larne, the French bauxite is crushed in a stone breaker, put through a "Tiger" mill and an Askham's separator, and roasted in a revolving calciner heated by a coal-fed grate; it passes from this into a rotatory cooler fitted with blades. The roasted ore is extracted with caustic soda in kiers holding about 1,500 gallons of liquor apiece and capable of treating I ton of ore. The alkaline extract is diluted and filtered. The sludge, which retains a certain amount of soda, is run on to "slob" grounds, and after settling, the supernatant liquor is pumped back. It contains some soda which would otherwise be lost; the recovery may well be due to carbonation while the sludge liquor is exposed to the air. The filtered liquor is ready for precipitation, which is done by the Bayer process. Formerly alumina was made from sodium aluminate by throwing it down FIG. 3. makes the question of the supply of cheap and good alumina of vital importance to the maker of aluminium. From the description given above it is clear that the present processmust be worked with much skill and care, and at the best cannot fail to be costly. It is probably not far from the truth to say that the cost of alumina is about one-third the total manufacturing cost of aluminium produced from it. Any mode of cheapening its production is therefore of considerable moment. In the early days of electrolytic manufacture of aluminium, salts such as the chloride or fluoride, either of aluminium alone or of aluminium and an alkali or alkaline earth metal, were electrolysed in vessels heated from without. It was soon found that no practicable material was capable of withstanding the heat from without and the corrosion from within, FIG. 4. with carbonic acid; more lately it has been found possible to take advantage of the fact that sodium aluminate is a highly unstable compound, and its decomposition can be determined by adding to its solution a little preformed alumina. This is carried out in practice by not completely emptying the precipitating tank, so that the fresh liquor from the extractors is brought at once into contact with alumina from the previous precipitation. As only about one-fifth of the total quantity of alumina present is precipitated by the Bayer process, there is a very large volume of aluminate solution continually going round and round. Seeing that this has to be concentrated to make it strong enough to extract a fresh quantity of bauxite and diluted again for filrering and precipitating, it is evident that large volumes of water have to be evaporated. The precipitated alumina is washed, dried, and calcined. It is almost chemically pure. The fact that alumina contains only about half its weight of aluminium, and that to produce pure metal pure alumina must be used, due to the electrolyte or its products. Hence in a short time all processes which succeeded in attaining a working footing were made dependent on the heating effect of the current itself. Two simple forms due to Minet illustrate the principle clearly. In Fig. 3, fused aluminium itself forms the cathode and the anode is of carbon. In Fig. 4 the reduced aluminium is not connected electrically with either pole, but in the bath are two carbon electrodes between which the current flows with sufficient intensity to keep the electrolyte fused. In the original Hall apparatus external heating was adopted, but it was soon given up and the present apparatus is certainly one in which the heating is internal. The early Héroult apparatus was devised to produce aluminium alloys. The history of its development as told by Héroult himself is informative and may be quoted. Héroult first tried to obtain aluminium by the electrolysis of aqueous solutions; he erred in this, having paid insufficient attention to thermo-chemical data, but quickly realising the impracticability of such a method passed on to the use of fused salts. At the date of his first experiments the apparatus available was far from perfect. Good carbon electrodes could scarcely be obtained, and when a carbon crucible was wanted it had to be laboriously ground out of retort carbon. Héroult's notable discovery that alumina could be electrolysed in a bath of haloid salts occurred curiously. He found that the anode was attacked in an electrolyte of the double chloride of sodium and aluminium and came to the conclusion that an oxide must be present; this oxide proved to be alumina derived from the decomposition of the aluminium chloride by moisture. It was but a short step from this to add alumina deliberately to the bath and to electrolyse it with corresponding destruction of the carbon anode. But at the time (1886-1887) the outlook for aluminium as a commercial metal was not particularly bright. No less an authority than Pechiney of Salindres told Héroult that aluminium might find a use for such articles de luxe as opera glasses; for serious purposes it hardly counted. Now it is an economic law that the more costly an article de luxe, the more freely it sells; hence attempts to reduce the price of aluminium could only lead to the impoverishment of everyone concerned, except the buyer, and he hardly counts. But Pechiney held that aluminium bronze was a useful alloy with large mechanical possibilities. acquainted with the matter will agree with this belief, and it has been a matter of wonder to me that even now when aluminium is cheaper than could be guessed 20 years ago, so little of this excellent alloy is made. was in consequence of this depreciation of aluminium and this extolling of its copper alloy that the first Héroult furnace for the production of aluminium bronze was patented. All It The whole of this description by Héroult of the line of thought and work which he followed is very interesting and curious, and it is worth while to pursue the matter a little further and hear his views on the process of electrolysis which occurs in the modern aluminium furnace. Although it is generally believed that in the electrolysis of a typical aluminium bath consisting of cryolite in which alumina is dissolved, it is the alumina that is electrolysed, an alternative view is possible. If pure cryolite is electrolysed, aluminium is obtained but not fluorine; the electrolyte is found to contain acid sodium fluoride according to Héroult. (The source of the hydrogen for NaFHF is obscure.) By using a higher temperature no aluminium is obtained, but sodium comes off freely. On these grounds Héroult concludes that the primary course of electrolysis is the separation of sodium which reduces aluminium from its fluoride; the necessary supply of aluminium fluoride is regenerated by the joint action of fluorine (or of fused compounds containing more than their normal proportion of fluorine) on alumina in the presence of carbon, precisely as aluminium chloride is prepared by acting with chlorine on a heated mixture of alumina and carbon. The weak point in this argument is that we have to postulate the existence of a sort of perfluoride of sodium, or rather a fluoride corresponding with the ordinary acid fluoride NaFHF, but containing no hydrogen and having the constitution NaFFF. FIG. 5. At present there is no evidence of the existence of such a body, and pending its being laid on the table, I, for one, prefer to regard the reaction in the Héroult bath as an electrolytic decomposition of alumina dissolved in cryolite. From a practical point of view, the matter is of minor importance. Into a bath of mixed fluorides of sodium and aluminium, provided with a carbon anode, alumina can be fed, and can be electrolytically decomposed with the production of aluminium and carbon monoxide and without the liberation of fluorine. A comparatively shallow iron box is lined with carbon blocks; old anodes fitted and cemented together serve very well. In the floor of the box is an iron plate by which the current is conveyed, so that the carbon floor forms a cathode, and there is no particular temptation for the current to wander about in the lining at large. Deposition of aluminium in casual places is thus avoided to a great |