Nov., 1921.1 U. S. BUREAU OF STANDARDS KOTES. 673

The elevators are classified into three groups : Class A, ele- \-ators located in buildings in which the service is heavy and Lvhere maintenance service is provided; Class B, buildings in which the service is heavy, but where no maintenance service is provided ; and Class C, buildings in which the service is light and in which no maintenance service is provided.

The data which were secured in various parts of three states and a number of large cities, are classified under the above group- ing, the performance in each group being briefly discussed.

The difference between an electromechanical interlock and a contact device is clearly pointed out and the functions and usual method of operation of each type of device is given.

The comparison of advantages and disadvantages and a com- parison of service of each of the three types are given in tabular form. Some suggestions as to possible improvement are added.

Representative statistics of elevator accidents are given: Group I.-Accidents from the entire United States reported by the public press through clipping bureau; Group II.-Industrial elevator accidents reported by various state departments of labor or state industrial boards (these accidents cover employees only) ; Group III.--Accidents to the public and employees reported by the coroners’ offices or elevator inspection departments of large cities.

These statistics have all been reclassified as non-shaft-door and shaft-door accidents, the latter being those that should he eliminated by the use of interlocking devices.

2% table of weighted averages of all the statistics is added and shows that 73.8 per cent. of all fatal accidents would probably be eliminated by the use of well-designed interlocks.

The report quotes the A. S. M. E. Elevator Code specifications for interlocks in conclusion.

Electric Furnace Treatment of Nickel-silver.-Among the alloys for which the electric furnace treatment seems best is nickel-silver, as pointed out in a paper by Thompson, presented to the American Electrochemical Society at its last (fortieth) meeting. The specific advantages observed here are: The loss of zinc IS less than I per cent., the occulsion of gases is minimized, a tougher alloy with less carbonization is obtained. Figures are given showing the avidity with which the alloy will absorb car- bon from a graphite crucible as contrasted with one of clay. Thompson also states that in his opinion the electric furnace has

674 CURRENT TOPICS. [J. F. I.

advantages when large quantities of scrap are to be remelted, in minimizing the accumulation of sulphur and carbon, and thus reducing the amount of virgin metal required for the charge.

H. L.

The Age of the Earth.-This question was the subject of a formal discussion at the recent meeting of the British Associa- tion for the Advancement of Science. Lord Rayleigh made the opening remarks, relriewing the methods that have been pro- posed. Lord Kelvin’s calculations based on a limit of the sun’s heat and the internal heat of the earth have been upset by the discovery of radioactivity. Lord Kelvin gave but a limited dura- tion to the period in which the earth was cool enough to support the life that is now on it, a result which was not acceptable to many geologists and paleontologists, who believed that the e\:i- dence of the fossil remains indicated a much longer period. Darwin termed Kelvin’s result “an odious spectre.”

The changes undergone by uranium have been recently made the basis of calculation, and especially the accumulation of lead in uranium-containing minerals. The upshot of the calculations at hand is a moderate multiple of one billion years as the time during which the earth was suitable for living beings, and data from physics or astronomy afford no definite presumption against this vie\\r. Rayleigh waives any discussion of the biologic and geologic data.

J. W. Gregory says that the best-known geologic estimates require to be multiplied ten or twenty-fold in order to agree with the physical estimates. A. S. Eddington suggests that Lord Kelvin’s time-scale should be lengthened five-huntlretl-foltl, at least during the stage of evolution. Gregory makes a curious mistake in saying that the claim that geologic time covered only a few score million years was regarded by geologists as of little more use than the “ seven days of the Pentateuch.” The creation, however, is given in the Pentateuch as having taken only six days.

H. L. Electrolytic Corrosion of Lead-Thallium Alloys.-Fink and

l<ldritlge in a communication to the recent (fortieth) meeting of the American Electrochemical Society report experiments undertaken with a view to minimize the loss of metal in anodes used in procedures of copper precipitation in Chile. It was found that an alloy of 70 per cent. lead, 20 per cent. tin and IO per cent. thallium lost only 1.2 pounds per IOO pounds of copper precipi- tated. It was also found that, in general, alloys with high melting points are more resistant to corrosion. The liquid subjected to electrolysis in the operations studied was a solution of copper sulphate containing nitric and hydrochloric acids. The low cor- rosion is due to a strongly adherent film formed on the anode.

1-I. L.