≈Phosphorus≈ 69 ≈Sulphur≈ 70 ≈Elements Which Have Become Especially Associated with Special Alloy Steels≈ 70 ≈Chromium≈ 70 ≈Tungsten≈ 72 ≈Molybdenum≈ 73 ≈Vanadium≈ 73 ≈Cobalt≈ 74 ≈Uranium, Titanium and Aluminum≈ 75 ≈Impurities≈ 75 ≈Heat Treatment≈ 76 ≈Hardening≈ 77 ≈Annealing≈ 79 ≈Tempering≈ 81 ≈Conclusion≈ 84 CHAPTER VI. ≈What Tool Steel Is Doing Towards Winning the War≈ 85 APPENDIX. ≈Analysis, Uses and Heat Treatment of Various Grades of Tool Steels≈ 92 ≈High Speed Steels≈ 93 ≈Die Steel for Hot Work≈ 94 ≈Special Alloy Steel≈ 95 ≈Semi-High Speed Steel≈ 96 ≈Simple Carbon Tool Steel≈ 97 ≈Non-Shrinking Oil Hardening Steel≈ 98 ≈Special Hot Work Alloy Steel≈ 99 A FEW SECRETS OF THE METALLURGIST SIMPLY TOLD INTRODUCTION. When as a student at a Technical College of one of our great Universities, I came to the study of Differential and Integral Calculus, I remember that I was seized with a kind of mental paralysis at the thought of the great unknown that lay before me. Fortunately, however, a little book was brought to my attention, under the encouraging title “Calculus Made Easy”. As a matter of fact the little volume did not attempt to take its readers through all the intricacies of the entire subject, but it did succeed in giving a certain start on the long journey which has to be undergone by a student of the Calculus. Its opening sentence was encouraging, which I have always remembered, and which read something as follows: “What one fool can accomplish, another fool can do, therefore take courage”. This same thought applies to the subject which is now before us. CHAPTER I. A SLIGHT TEST OF THE IMAGINATION. We live in a world in which certain conditions of the atmosphere and the so-called elements surrounding our daily existence, are entirely familiar to us. From force of habit we are likely to forget that had Nature, for instance, been planned under a different range of livable temperatures, all the familiar objects of our daily existence would have existed under entirely different form.