Fourth. Heat-treated eye-bars of high-grade nickel-steel are probably economic for all span less than 3,000 feet.

Fifth. If satisfactory eye-bars can be made of heat-treated "Chromol" steel, and having an elastic limit exceeding 100,000 lbs. per square inch and an ultimate strength of not less than 150,000 lbs. per square inch, they will be more economical than wire cables for suspension bridges of any feasible span-lengths.