"This seems to be a universal law in the compounding of metals. Very few metals are used alone in the various arts and manufactures. For every purpose some combination has been found which makes the product better. Even coins are so alloyed. Silver and gold in the form of money would be entirely too soft, unless alloyed with some hardening metal. Some substances, like arsenic, antimony and bismuth, are too brittle to be used alone. The only metals which can be used alone are aluminum, zinc, iron, tin, copper, lead, mercury, silver, gold and platinum."
"What is bronze, of which all the ancient guns were made?"
"That is a combination of copper and tin. This product was known fully seven hundred years before the Christian era, and was used in the making of guns until superseded by the various steel alloys of our day."
"In what proportions are copper and tin united to make bronze?"
"The proportions vary greatly. Ancient Celtic bronze had 12 parts tin and 88 of copper; Egyptian, 22 tin, 78 copper; Chinese, 20 tin, 80 copper; Roman, 15 tin, 85 copper; and in many specimens lead and zinc were also used. Tin has a capacity to harden almost any metal."
"What is the best metal to harden steel?"
"Manganese, of which you will remember we have some samples; it is the most serviceable, as we have neither nickel nor chromium."
"What amount of that metal should we use to get the best results?"
"About 14 per cent. of manganese has been found the best for such purposes as would be required in gun barrels. There is a curious thing which has been discovered in uniting manganese with steel. It becomes fairly tough if 1 per cent. is used with the steel; if the quantity added is between 1-1/4 and 3-1/2 the strength and ductility decrease; but above that, up to 5 per cent., the steel becomes brittle; above 6-1/2 per cent. it again returns to ductility and toughness and its maximum strength is found at 14 per cent."
During the evenings all took a hand at cutting out the stocks for the guns, and the plans upon which they were constructed will be fully explained and illustrated in the order of the work done.