THE RARER METALS AND THEIR ALLOYS. 513 



remarkable properties; in fact, as he told me, if nature had properly 

 understood Mendeleef this alloy would really have been an element. 

 As regards the electrical properties of alloys, it is impossible to say 

 what services the rarer metals may not render; and I would remind 

 you that "platinoid," mainly a nickel copper alloy, owes to the presence 

 of a little tungsten its peculiar property of having a high electrical 

 resistance which does not change with temperature. 



One other instance of the kind of influence the rarer metals may be 

 expected to exert is all that time will permit me to give you. It relates 

 to their influence on aluminum itself. You have heard much of the 

 adoption of aluminum in such branches of naval construction as 

 demand lightness and portability. During last autumn Messrs. Yar- 

 row completed a torpedo boat which was built of aluminum alloyed 

 with per cenV of copper. Her hull is 50 per cent lighter and she is 

 33 knots faster than a similar boat of steel would have been, and, not- 

 withstanding her increased speed, is singularly free from vibration. 



Her plates are one-tenth of an inch thick and one-sixth of an inch 

 where greater strength is needed. It remains to be seen whether copper 

 is the best metal to alloy with aluminum. Several of the rarer metals 

 have already been tried, and among them titanium. Two per cent of 

 this rare metal seems to confer remarkable properties on aluminum, 

 and it should do so according to the views I have expressed, for the 

 cooling curve of the titanium-aluminum alloy would certainly show a 

 high subordinate freezing point. (Fig. 3, PI. XXYI.) 



Hitherto I have appealed to industrial work rather than to abstract 

 science for illustrations of the services which the rarer metals may 

 render. One reason for this is that at present we have but little knowl- 

 edge of some of the rarer metals apart from their association with car- 

 bon. The metals yielded by treatment of oxides in the electric arc are 

 always earburized. There are, in fact, some of the rarer metals which 

 we as yet can hardly be said to know except as carbides. As the fol- 

 lowing experiment is the last of the series, I would express my thanks 

 to my assistant, Mr. Stansfield, for the great care he has bestowed in 

 order to insure their success. Here is the carbide of calcium which is 

 produced by heating lime and carbon in the electric arc. It x'ossesses 

 great chemical activity, for if it is placed in water the calcium seizes 

 the oxygen of the water, while the carbon also combines with the 

 hydrogen, and acetylene is the result, which burns brilliantly. [Experi- 

 ment shown.] If the carbide of calcium be placed in chlorine water 

 evil-smelling chloride of carbon is formed. 



In studying the relations of the rarer metals to iron it is impossible 

 to dissociate them from the influence exerted by the simultaneous 

 presence of carbon; but carbon is a protean element — it may be dis- 

 solved in iron, or it may exist in iron in any of the varied forms in 

 which we know it when it is free. Matthiessen, the great authority on 

 alloys, actually writes of the "carbon-iron alloys.' 7 I do not hesitate, 

 SM 96 33 



