A. By friction and cohesion.
Q. When would you oil an engine?
A. Before starting it and as often while running as is necessary.
Q. What is the tensile strength of American boiler iron?
A. 40,000 to 60,000 pounds per square inch.
Q. What are the principal defects found in boiler iron?
A. Imperfect welding, brittleness, low ductility.
Q. What is the advantage of steel as a material for boiler plate?
A. Tensile strength, ductility, homogeneity, malleability and freedom from laminations and blisters.