July 1, 1896.] 



KNOWLEDGE, 



149 



but, practically, one pound of carbon is consumed per 

 pound of aluminium formed, and this quantity is obtained 

 per hour from each pot. The pots themselves and their 

 linings last for months of continuous work. Unlike many 

 industrial processes, there are no bye-products or slag, and 

 there is no volatilization of the metal. The Pittsburgh 

 works are only about half a mile from the Niagara Falls, 

 so that the cun-ent is obtained directly from the mains of the 

 Niagara Falls Power Company. This current is alternating, 

 but it is converted into a direct one and its voltage is 

 lowered by transformers at the works. The aluminium 

 produced in America is of high comparative purity, the 

 average percentage of the metal being ninety-nine and 

 upwards. The chief impurities are siUcon and iron, and its 

 commercial value is now about thirty-iive cents per pound. 



In Switzerland and France the process adopted is that 

 which was patented by P. L. V. Hcroult. As to the 

 priority of these patents, it is interesting to note that the 

 cryolite process was first proposed by Henderson, an 

 Englishman, in 1886, but he never put his process into 

 practice. The Heroult process, as will be seen from the 

 following description, is based on exactly the same prin- 

 ciple as that involved in the patents taken out by Hall, 

 although both these inventors worked independently of 

 one another, and about the same time applied for the 

 American patents ; but on investigation it was found that 

 Hall had produced the first aluminium on February 23rd, 

 188C>, whereas Heroult named only the date of his French 

 patent of April i'dvi, 1 880. 



Huroulfs first French patent deals with the production 

 of pure aluminium. He places a mixture of alumina and 

 cryolite in a carbon crucible surrounded by a larger one, 

 the space between the two being filled with graphite. The 

 positive electrode consists of a thick carbon rod which 

 dips into the molten mass. A current of three volts is 

 used by this inventor, but in other respects the process is 

 similar to that of Hall. 



By slight alterations in the working of the process it 

 can be made available for the production of aluminium 

 alloys. This consists in using a negative electrode of the 

 metal — say copper — with which it is wished to form an 

 alloy, when, as the current passes, the aluminium alloy is 

 regularly formed, and collects as a melted button at the 

 bottom of the crucible. It would seem that Heroult hardly 

 realized the importance of his invention towards cheapening 

 the production of pure aluminium, as at this time he gave 

 his chief attention to his alloy patent. This was acquired by 

 the Society Metallurgique Suisse, at Neuhausen, and proved 

 so satisfactory that the firm at once decided to use it for 

 the manufacture of aluminium bronze on a very large scale. 



The usual bronze contains forty-two per cent, of 

 aluminium, and from it, by the addition of copper, alloys of 

 different grades are produced in ordinary smelting furnaces. 

 In 1888 the Societe ElectrometaUnrgique Suisse was 

 converted into the present Aluminium Industrie Actien 

 GeseUschaft, and the bronze plant was then augmented so 

 as to yield one thousand kilos of bronze daily. Encouraged 

 by the success of Hall's process in America, Heroult, in 

 conjunction with Kiliani, returned to his original process 

 for the production of the pure metal, and soon succeeded in 

 so improving his process that the Neuhausen company were 

 enabled to erect additional plant, which already turns out 

 five thousand five hundred pounds of commercially pure 

 aluminium daily, and the new process has now almost 

 entirely superseded the alloy process. In 1888 the Societe 

 Electrometallurgique Fran<,'ai3e, at Froges, acquired the 

 right to use the Heroult patents, and has since had a daily 

 output of three thousand kilos of alloy, and has produced 

 some fifty thousand kilos of pure nluraiuium per annum. 



Tne British Aluminium Company, to which reference 

 has been made, has only been in existence a short time, 

 but has already erected plant at Larne for the treatment 

 of their deposits of Irish beauxite, and are engaged upon 

 the erection of reduction works at the Falls of Foyers and 

 of metallurgical workshops at Milton. It is diflScult, how- 

 ever, to predict the direction in which this English industry 

 will develop, as at present no information has been pub- 

 lished as to which electrolytic processes are to be employed. 

 The statement of the chairman of the company that " the 

 natural advantages of the Strath were even greater than 

 those of Niagara, for the fall of water to Loch Ness was 

 very much greater," remains to be proved. 



Sufficient has been said to show that since the Paris 

 Exhibition of 18.3.3 the progress in this particular Industry 

 has been enoi-mous, but a few statistics as to the total 

 output may not be out of place. 



According to Richards, the world's production up to 

 1892 was only two million five hundred and eighty-six 

 thousand pounds ; but in 1893 one million four hundred 

 and seventy-four thousand pounds were produced, and In 

 1891 two million two hundred and forty-four thousand 

 pounds. Last year the American output has been 

 estimated at eight hundred and fifty thousand pounds, and 

 it is believed that the production of the present year will 

 reach over two million pounds, as the Pittsburgh Reduction 

 Company will have ready by the 1st of June plant capable 

 of making ten thousand pounds per day. 



This increase has been accompanied by a reduction in 

 the price, so that from being, as at one time, a luxury, and 

 used as a cradle for the Prince Imperial of France and as 

 a helmet for the Crown Prince of Denmark, aluminium 

 can now be found in most houses. Amongst the many 

 uses to which it is at present applied may be mentioned 

 the following : military equipments, as water-bottles, spurs, 

 sword handles, helmets, and horseshoes ; naval purposes, 

 torpedo-boats and yachts being made of it for lightness ; 

 bicycles ; vehicles, autocars, etc. (an aluminium cab is 

 running in Paris) ; aerial machines ; besides numerous 

 smaller articles of domestic use, and especially surgical 

 and scientific apparatus. It wiU be seen that all these 

 difi'erent uses indicate a great future for the metal, espe- 

 cially as, of the more common metals, iron, zinc, nickel, 

 and copper are at present the only ones which are cheaper 

 than aluminium. 



SOME CURIOUS FACTS IN PLANT 

 DISTRIBUTION.-III. 



By W. BoTTiXG Hemslev, F.R.S. 



STILL continuing on insular floras, I would say 

 something about the Tristan d'Acuuha group in 

 the South Atlantic, in latitude 37', and longitude 

 12° W. ; and St. Paul and Amsterdam Islands, in 

 the Indian Ocean, in almost exactly the same 

 latitude as Tristan d'Acunha, and about 77' 30 E. 

 longitude, or in round numbers five thousand miles dis- 

 tant, with no land intervening in the same latitude. 

 The history of botanical discovery in these islands is so 

 intensely interesting that one is tempted to dwell on it ; 

 but I must be content to give the reader a taste only. The 

 Tristan d'.\cunha group consists of three islands only a 

 few square miles in extent, yet one of them towers to the 

 height of eight thousand feet. The main island has had a 

 small population for some years. Amsterdam Island is 

 larger — some six miles across — but rises only to a height 

 of two thousand seven hundred and sixty feet. St. Paul is 

 smaller, and less than eight hundred an.l fifty feet high. 



