THE RARER METALS AND THEIR ALLOYS. 507 



indebted to M. Moissan for sending ns beautiful specimens of chromium, 

 vanadium, uranium, zirconium, tungsten, molybdenum, and titanium. 

 [These were exhibited.] 



The question naturally arises, Why is the future of their usefulness 

 so promising? Why are they likely to render better service than the 

 common metals with which we have long been familiar 1 ? It must be 

 confessed that as yet we know but little what services these metals will 

 render when they stand alone; we have yet to obtain them in a state 

 of purity, and have yet to study their properties, but when small 

 quantities of any of them are associated or alloyed with other metals 

 there is good reason to believe that they will exert a very powerful 

 influence. In order to explain this, I must appeal to the physical 

 method of inquiry to which I have already referred. 



It is easy to test the strength of a metal or of an alloy; it is also easy 

 to determine its electrical resistance. If the mass stands these tests 

 well, its suitability for certain purposes is assured; but a subtle method 

 of investigation has been afforded by the results of a research intrusted 

 to me by a committee of the Institution of Mechanical Engineers, over 

 which Dr. Anderson, of Woolwich, presides. We can now gather much 

 information as to the way in which a mass of metal has arranged itself 

 during the cooling from a molten condition, which is the necessary step 

 in fashioning it into a useful form; it is possible to gain insight into the 

 way in which a molten mass of a metal or an alloy molecularly settles 

 itself down to its work, so to speak, and we can form conclusions as to 

 its probable sphere of usefulness. 



The method is a graphic one, such as this audience is familiar with, 

 for Prof. Victor Horsley has shown in a masterly way that traces on 

 smoked paper may form the record of the heart's action under the dis- 

 turbing influence caused by the intrusion of a bullet into the human 

 body. I hope to show you by similar records the effect, which, though 

 disturbing, is often far from prejudicial, of the introduction of a small 

 quantity of a foreign element into the "system" of a metal, and to 

 justify a statement which I made earlier as to the applicability of 

 physiological methods of investigation to the study of metals. In order 

 that the nature of this method may be clear, it must be remembered 

 that if a thermometer or a pyrometer, as the case may be, is plunged 

 into a mass of water or of molten metal, the temperature will fall con- 

 tinuously until the water or the metal begins to become solid; the tem- 

 perature will then remain constant until the whole mass is solid, when 

 the downward course of the temperature is resumed. This little 

 thermo-j unction is plunged into a mass of gold, an electric current is, 

 in popular language, generated, and the strength of the current is pro- 

 portional to the temperature to which the thermo-j unction is raised; so 

 that the spot of light from a galvanometer to which the thermo-j unction 

 is attached enables us to measure the temperature, or, by the aid of 

 photography, to record any thermal changes that may occur in a heated 

 mass of metal or alloy. 



