The words âat least 17 years of age and *â*â* under 45 years of ageâ are substituted for the words âwho shall be more than seventeen years of age and *â*â* not more than forty-five years of ageâ.
Steel is cheaper, and brass is more expensive, and not much of a structural material. Brass is a tensile metal, and has a great ability to bend. It is used to make bearings, valves and moving parts, because it does not break easily. Steel, on the contrary, is difficult to cast, and quite difficult to work with in small machines.
Brass is usually made up of copper and zinc. Some alloys are called bronze when they are actually brass, such as commercial bronze which is made from copper and zinc. Other metals may also be added, but if the main addition is tin, it's a bronze, and if the main addition is zinc, it's a brass.