of the largest alloy-steel manufacturers and consumers in the United States, with the result that it met with their approval—their experience with the various molybdenum-steel types described conforming to the statements, facts, and figures set forth. Moreover, the general treatment of the subject gives prima facie evidence of a spirit of fairness; and the style of work is that of a technical scientist and not that of a promoter.

Unfortunately, the records all deal with heat-treated steel, which, while applicable for eye-bars, is not suitable for built members of bridges; but by inquiry from the writer of the pamphlet the author obtained a small amount of data concerning tests of one of the steels untreated, as well as some results of tests of carbon-molybdenum steel that were made on an accidental melt from which chromium had unintentionally been omitted. From the same source it was learned that the proportionate increase in ultimate strength and elastic limit due to the addition of molybdenum is practically the same for untreated as for treated steels.

From the contents of the pamphlet, the additional information just mentioned, and the author's previous experience with nickel steel, the deductions which follow have been drawn.

For simplification of the discussion, and in order to distinguish readily between the various combinations of alloying materials, the author has taken the liberty of evolving and using the following nomenclature:

Carmol     = Carbon-Molybdenum.

Chromol    = Chromium-Molybdenum.

Nichromol   = Nickel-Chromium-Molybdenum.

Nicmol     = Nickel-Molybdenum.

Chrovanmol = Chromium-Vanadium-Molybdenum.

Nichro     = Chrome-Nickel.

Chrovan    = Chrome-Vanadium.

In order to utilize the diagrams of this chapter for finding the economics of molybdenum as an alloying material for bridge steel, an understanding will have to be arrived at, in order to determine properly the values of r' ; because, while a high intensity of working stress may be employed for heat-treated eye-bars, a much lower one will have to be adopted for the untreated built-members; and, again, it would never be legitimate to use a working stress greater than one third of the ultimate strength. In heat-treated steels the elastic limit generally falls but little below the ultimate strength,hence it would not do to use one half of its amount for the working tensile stress as is done in the case of untreated steel.

As the data concerning the untreated molybdenum steel are rather meagre, it will be necessary to make a few approximate assumptions in determining the elastic limits and intensities of working stresses. For instance, one is that the proportion of untreated and treated steel in a pin-connected bridge will be about as two is to one. This is fairly accurate, and will suffice for  a  preliminary  study  of  which  the  sole  purpose  is  to  indi-