October 31, 1901] 



NA TURE 



size of our machinery, owing to its bulk (diameter nearly 

 30 per cent, greater than equivalent copper) ; but it will 

 now always act as a check upon the artificial raising of 

 the price of copper. 



The high cost of insulating materials renders it un- 

 likely that aluminium with its;greater size will ever replace 

 copper in insulated cables. And even as a bare con- 

 ductor, it is doubtful what advantage in price (together 

 with whatever saving may come from having wires only 

 half as heavy to handle and support) will compensate for 

 the many disadvantages as compared with hard-drawn 

 copper — greater liability to corrosion, difficulty of 

 making joints, less tensile strength (even of aluminium 

 bronze), lack of uniform quality, greater surface exposed 

 to the wind, greater unsightliness owing to size (for trolley 

 wires), &c. 



Still, the excessive price of copper which has obtained 

 during the last two years, and indeed till a few months 

 ago, has led to the putting down of between one and 

 two thousand tons of bare aluminium conductors for 

 electric-power transmission — chiefly in America, and for 

 very high-tension, long-distance schemes — schemes, in 

 fact, in which the cost of the lines represents the greatest 

 proportion of the whole expenditure. 



The experience as to the behaviour of aluminium 

 already gained from these installations is very valuable, 

 as may be gathered from a perusal of two recent papers 

 — one read by Messrs. Perrine and Baum before the 

 American Institution of Electrical Engineers, and the 

 other by Mr. Kershaw before our own similar Institution. 

 The former writers find that, owing to a large tempera- 

 ture change in the elastic constant, the true coefficient 

 of expansion of the new metal is not applicable in calcu- 

 lations of stresses in suspended wires having a given 

 sag, the apparent temperature effects being much less 

 than those calculated. Again, in the latter paper it is 

 suggested that aluminium will not weather so well in this 

 country as in the drier climate of .\merica. It would 

 seem also as if, while good soldered joints are quite 

 possible with the metal, only welded or "burnt" joints 

 involving no solder are durable out-of-doors, the metal 

 being so highly electropositive, and the alloys formed 

 near soldered joints unstable. Mechanical joints are 

 generally used in America. The Mclntyre joint is made 

 by slipping the ends into a flat aluminium sleeve, the 

 whole being then twisted round twice or thrice. It is 

 doubtful whether such joints retain their initial high con- 

 ductivity, in view of experience with similar joints in 

 telegraph work. As an electrical conductor, then, it is 

 only in those rare cases where conducting power for a 

 given weight is wanted, irrespective of volume, that 

 aluminium is without question the best material to use. 



For structural purposes, the new metal has up to the 

 present proved a little disappointing. In the first place, 

 the pure metal is useless, being too soft. This, however, 

 was to be expected. Pure iron is also soft. The alloys 

 with copper up to a density of 3 include some which seem 

 fairly strong ; but the fact that cycle frames are still 

 made of steel shows that, where strength and lightness are 

 required together, and cost is not of great moment, steel 

 •can still hold its own, apart from its relative cheapness. 

 No doubt, however, there is yet much to be learnt about 

 the metallurgy of the alloys with copper, and with other 

 elements also — nickel, tin, magnesium, &c. 



A considerable demand for aluminium has grown up in 

 connection with the manufacture of a great variety of 

 small articles, instruments, &c. The most important 

 uses of the metal from a commercial point of view are 

 based upon the activity of its reactions at a high tem- 

 perature. Added in small quantities to molten iron just 

 before a cast is made, the metal is rendered more fluid 

 and the quality of the casting thereby improved.' This 



1 See "The Relations of Aluminium to Iron," by Godfrey Melland 

 '{PriH. Staff. Iron and Steel Inst., 1900). 



NO. 1670, VOL. 64] 



result appears to be due to the reduction by the alu- 

 minium of any iron oxide which may be present, and to 

 the raising of temperature of the iron itself by the heat 

 of the action. It was stated by Swan, in a recent 

 presidential address in Glasgow, that this use of the 

 metal formed one of the chief outlets for the 6000 odd 

 tons of aluminium which were manufactured last year. 



The Goldschmidt process, by which the most intense 

 heat can be produced in any required amount at a given 

 point also depends upon the same fact, that aluminium 

 can reduce iron oxide with energy to spare. A mixture 

 of finely-divided aluminium and iron oxide, known as 

 " thermit," can be ignited by a suitable fiise, and results 

 in a quantity of molten iron heated far above the melting- 

 point and protected from combustion by a layer of 

 alumina. This iron, being so very greatly superheated, 

 will serve for a variety of purposes, and its quality can be 

 varied as required by suitable additions to the '■ thermit." 

 This process was lately described and demonstrated at 

 the Royal Institution by Roberts-Austen,' to whom, 

 indeed, it is largely due. It has been applied to the 

 welding of rail joints in position for electric traction, and 

 to the repairing of broken and of faulty steel castings. 

 The process has, in fact, many of the possibilities of the 

 electric furnace, without the drawback of being dependent 

 upon a fixed and costly electrical installation. 



THE OCTOBER ORION IDS. 



IN many previous years the Orionid radiant has been 

 well defined at a point very close to, if not coinciding 

 with, the position of the star v Orionis (mag. 4j). The 

 shower was very successfully observed by Prof. A. S. 

 Herschel on about October 18-20 in the years 1864, 

 1865 and 1S67, when the centre of divergence was found 

 to be at 90° -1-15°. A number of observations were 

 obtained at Bristol in 1877, 1879, 1887 and other 

 years, and the radiant derived from them was at 91" -F 15". 

 The meteors of this shower belong to the swifter class, 

 and they leave streaks which enable their directions of 

 flight to be so correctly noted that the centre of emana- 

 tion not only appears sharply defined, but can be very 

 accurately located. The streaks frequently linger for 

 two or three seconds and will sometimes very perceptibly 

 brighten up after the heads of the meteors have vanished. 



The observations in 1900 and 1901 made at Bristol 

 show that the true Orionids were feebly represented and 

 that, in fact, the annual shower-meteors fiom the old 

 position at v Orionis had been supplanted by a more 

 active radiant of Geminids agreeing in place with the star 

 ^ (ieminorum (mag. 3^). On October 23-27, 1900, and 

 October 20, 1901, 1 recorded about twice as many 

 meteors from 100^ -I- 13" as from 91' -f 15^ The ob- 

 servations were not very numerous, but had they been 

 far more complete there is no reason to suppose that the 

 conclusions would have been materially aflfected. 



The difference of 9 in the positions of the radiants at 

 V and ^ Orionis is sufficiently large to be immediately 

 detected by meteoric observers though their materials are 

 merely eye estimations. The latter are, however, un- 

 usually trustworthy, not only in the case of the Orionid 

 display, but also in regaid to some of its bordering and 

 contemporary showers which furnish similar objects. The 

 flash of a meteor's head as it darts rapidly along in a 

 state of combustion attracts the eye to the point of ap- 

 pearance, and the streak which immediately glows along 

 the path enables the observer to fix the apparent 

 direction of flight with almost instrumental precision. 



In the Monthly Notices for December 1895 (vol. Ivi. 

 p. 74) I mentioned the y Geminids as one ot the most 

 prominent companion radiants of the Orionids and gave 



1 "Metals as Fuel," Royal Institution Lecture (Nat URE, August 8, 

 1901). 



