From these assumed figures it appears that heat-treated, high-grade, nickel-steel eye-bars could probably be used economically for suspension- bridge spans up to at least 3,000 feet.

It is within the realm of possibility that in a few years there will be manufactured heat-treated, chrome-molybdenum-steel eye-bars having an ultimate strength of 150,000 lbs. per square inch, for which the intensity of working stress may be taken at 50,000 lbs. per square inch, corresponding to a minimum elastic limit of 100,000 lbs.; and that the metal in place will be worth not to exceed 15 cents per lb.

Let us test this for a 3,000-ft. span,

Heat-Treated Chrome-Molybdenum-Steel Comparison

3000-Foot Span.

Wire-Cable Structure

From these figures it is evident that the hypothetical "Chromol" steel at the hypothetical pound price used would be much more economical than wire for suspension bridges of all possible span lengths.

Résumé of Findings

Summarizing the results of the entire investigation, on the basis of present unit prices, the following conclusions are reached.

First. Neither untreated Mayarí-steel eye-bars nor heat-treated carbon-steel eye-bars can compete with wire in the building of highway suspension bridges.

Second. If Mayarí-steel eye-bars after being heat-treated are reliable and satisfactory, it is not unlikely that they can compete with wire cables for spans up to 2,000 feet.

Third. Untreated eye-bars of high-grade nickel-steel are more economic than wire for spans up to 1,400 feet.