Manufacturer and builder 9, 1873
The first question has been answered in our August number for 1871, Query 150, page 191. The answer to the second may be deduced from communications on tempering steel so as to produce colors varying from yellow to blue, (see our second volume on pages 54 and 303, and in this volume, page 107.) The barrel is simply cleaned and polished, then it is carefully exposed to the proper degree of heat, some 550°, when it will first become yellow, then darker yellow, and finally blue, when it is removed from the fire. It is an operation which requires proper appliances, with experience, and dexterity, so as to produce an equal color over the whole length of the barrel.
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