ported that these tools compare favorably in edge-holding qualities with forged or bar machined stock, and that it may be forged into various shapes when necessary. The large saving in time and material in finish-machining such tools is at once apparent to any practical shopman. This company also casts bars and billets for various purposes.
The company does not machine the tools, but supplies them to shops as ordered, just enough extra metal being allowed to clean up well and give a good edge where needed. The tools are cast from patterns exactly as if pouring from cast iron, and, after being cleaned and carefully annealed, are ready for delivery. The heat treatment recommended is as follows : Bring the steel slowly to 65o ยฐ F., raise to i2oo, then raise quickly to 225o and quench in fish oil until cool. If a gas furnace is used, supply more gas than air in order to prevent the steel from acquiring a soft cutting edge.
Progress in A'~rial Navigation. SANTOS-DUMoNT, (Flying, vol. vi, No. I, p. 3 I, February, I917.)--On the I4th of July, 19o3, the author piloted a dirigible at the Longchamps military manoeuvres in which IOO,OOO troops took part. That was the first time a6rial navigation was a feature of a military demonstration. At that time it was predicted that a6rial warfare would be one of the most important