From molecular condition, as revealed by the microscope, down to the last petty detail in the plan of construction, there is never an end to the problems, and gravity has to be figured into the lifetime of a rope as surely as the elusive trace of sulphuric and muriatic acid producing hydrogen occlusion. Wire rope is a business of exactitude and eternal vigilance. You have to deal with breaking strengths of from 40,000 to 340,000 pounds to the square inch of transverse section, but the wire that will lift weights at the rate of more than a hundred tons has entirely different characteristics than the lower strength material. And the why of that must be traced back to the treatment of the steel when it was passing through the wire stage. Rope makers dealt with molecules once and thought they were taking pains. They found they had to go back to atoms to handle their problems. Today the secret seems to lurk in the electron. [Sidenote: FITTING THE ROPE TO ITS WORK] Of the tricks in making ropes, there is no end. They are fitted for their work like a soldier or a gymnast, and built for it. A tiller rope must be flexible to the last degree, but it must be strong enough so it will stand up under the swift tensions of a storm or in the lightning manoeuvers of a race. Therefore, like a few ropes built for other purposes, the composite parts are not mere strands of wire, but little ropes in themselves, complete in all parts. And again, while ropes exposed to weather and stationary, like ships' standing riggings, are galvanized, those that are subjected to constant bending are not. For every variation, there's a reason. To the average man or woman, the elevators in tall buildings suggest danger. The rope engineer counts them highly safe because each elevator is equipped with a multiplicity of ropes and safety devices. What taxes his conscience and spurs him to the last possible effort, is the rope that goes to the "deep shaft" service, where the lives of men going up and down in five thousand feet or more of subterranean darkness, hang on the accuracy of his calculation. Only now, the Roebling engineers will tell you, is wire rope being perfected. Much of it is in what seem to be small details of construction, which nevertheless go down into the basic principles that make for efficiency. Rope making has been treated as an exact science, because it dealt with materials that were more or less standardized. They are learning now that rope has a large unknown quantity that defies formula past a certain point. For the lack of a better term, they call it "personality." The labor of today, and many years to come, is to identify these intangible factors and bring them where they can be computed to the end of securing greater endurance and safety. In the Roebling shops there are men working who got their jobs almost by heredity. Their fathers and grandfathers worked for John A. Roebling.