than to steel can readily be accounted for by the greater roughness of the puddled iron, due to its containing a small quantity of cinder widely scattered throughout it in minute particles, whereas steel contains none."

Steel is perhaps the most tenacious of all known substances—that is, tough—having great cohesive force between its particles, so that they resist any effort to pull or force them apart; and as we fancy all matter to be in a state of motion at all times, the difficulty in preserving it by use of a paint is at once apparent. The defects in modern structural steel are largely due to its mechanical working—that is, it is run out too hot and too quick, and afterward not properly housed and cared for. "The enormous increase of late  in  its  use  in  building  and engineering  construction  in  various  forms,