ADDRESS. 1 9 



•engineers look forward, with much interest, to all processes tending to 

 bring this metal, or its alloys, within possible commercial use ? 



One more instance of the effect of impurities in metals. The engineer 

 engaged in electrical matters is compelled, in the course of his daily- 

 work, frequently to realise the importance of the ' next-to-nothing.' One 

 striking instance of this is afforded by the influence which an extremely 

 minute percentage of impurity has on the electrical conductivity of copper 

 wire : this conductivity being in some cases reduced by as much as 60 

 per cent., in consequence of the admixture of that which, under other 

 •circumstances, would be looked upon as insignificant. 



Reverting to the question of big guns. According to the present 

 mode of manufacture, after we have rough-bored and turned the ' A ' 

 tube (and perhaps I ought to have mentioned that by the ' A ' tube is 

 meant the main piece of the gun, the innermost layer, if I may so call it, 

 that portion which is the full length of the gun, and upon which the 

 remainder of the gun is built up) — after, as I have said, we have rough- 

 bored and turned this 'A' tube, we heat it to a temperature lying 

 between certain specified limits, but actually determined by the behaviour 

 of samples previously taken, and then suddenly immerse it perpen- 

 dicularly into a well some 60 feet deep, full of oil, the oil in this well 

 being kept in a state of change by the running into it, at the bottom, of 

 cold oil conveyed by a pipe proceeding from an elevated oil tank. In this 

 way the steel is oil-hardened, with the result of increasing its ultimate 

 tensile strength, and also with the result of raising its so-called elastic 

 limit. In performing this operation it is almost certain that injurious 

 internal strains will be set up : strains tending to produce self- rupture 

 of the material. Experiments have been carried out in England, by 

 Captain Andrew Noble, and by General Maitland of the Royal Gun 

 Factory, by General Kalakoutsky, in Russia, and also in the United 

 States, to gauge what is the value, as represented by dimensions, of these 

 strains, and we find that they have to be recorded in the most minute 

 fractions of an inch, and yet, if the steel be of too ' high ' a quality (as it is 

 technically called), or if there has been any want of uniformity in the 

 oil-hardening process, these strains, unless got rid of or ameliorated by 

 annealing, may, as I have said, result in the self -rupture of the steel. 



I have spoken of the getting rid of these strains by annealing, a 

 process requiring to be conducted with great care, so as not to prejudice 

 the effects of the oil-hardening. But take the case of a hardened steel 

 projectile, hardened so that it will penetrate the steel face of compound 

 ai'mour. In that case annealing cannot be resorted to, for the extreme 

 hardness of the projectile must not be in the least impaired. The internal 

 strains in these projectiles are so very grave, that for months after they 

 are made there is no security that they will not spontaneously fractare. I 

 have here the point of an 8-inch projectile, which projectile weighs 210 lbs., 

 this with others was received from the makers as long ago as March of 



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