CURRENT TOPICS.
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been found recently that metal surfaces carefully freed from gases do not exhibit any appreciable photo-electric effect. It seems therefore, as if the process of electronic emission from cold metal surfaces could take place only through the intermediary of the surface-layer of gaseous molecules." G.F.S.
Wider Highway Tendency Shown in Road Building. (U. S. Department of Agriculture Press Service No. z94.)--Of 65oo miles of completed Federal-aid road for which statistics have been collected by the Bureau of Public Roads, United Stats Department of Agriculture, one-half has been constructed of 16 and I8-foot width, 25 per cent. of a greater width, and 25 per cent. of a less width. As would be expected the wider roads have been constructed largely in the more populous States, although some of the less populous States are building wider roads for the main highways. There is a general tendency, it is said, to build wider roads to meet the needs of the constantly increasing traffic, as shown by the 25 per cent. of the mileage over 18 feet in width, 7 per cent. being 24 feet or wider.
Wider Bridges for Roads. ( U. S. Department of Agriculture Press Service No. 193.)--Few highway bridges with a width of roadway less than 18 feet are now being constructed on improved roads, according to engineers of the Bureau of Public Roads of the United States Department of Agriculture. In the past some of 12 feet and a good many of I6-foot width have been constructed in an effort to economize but it has proved short-sighted economy. Only one line of traffic can pass over a I2-foot roadway and 16 feet of width will not accommodate two lines in safety. Many of the States such as Pennsylvania, New Jersey, Ohio, and Massachusetts have found it advisable in replacing old bridges on important roads to make them wide enough to accommodate three and four lines of traffic.
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