IN the companion issue, No. 1860, of our SUPPLEMENT, Harold J. Shepstone contributes an article on the Potter's Clay Industry.A very interesting suggestion for a new method of estimating the duration of geological ages is made by Mr. Arthur Holmes. We bring some new information regarding that important modern development, the Diesel engine, as applied to marine use. The electrolytic smelting of iron has for some time been attracting attention. Consul L. J. Fuller, of Gothenburg, Sweden, reports on the prod uction of pig iron by electricity. The applica tion of me tallo-graphic diagnosis to the effect of mechanical treatment on the structure of metals is discussed by our Paris correspondent. The ffth instalment of Donald Murray's article on Printing Telegraphy appears in this issue. The electric locomotive for the line running through the tunnel in the Lotschberg is described by our English correspondent. Mr. Feldhaus gives us an illustrated account of the “Evolution of the Umbrella.” Prof. Wiener discusses some of the dangers of aeronautics, and remedies against them.-R. A. Smith gives an account of the highways wtich the Romans built through and about the present site of London.-A. E. Outerbridge discusses the uses and limitations of manganese and silicon in foundry practice. An Exhibition of Labor-saving Appliances THE United States Government Exhibit of Labor Saving Office Appliances was held on two floors of the Union Building in Washington city, July 6th to 15th, and the display is said to have equaled those of the Madison Square Garden and the Chicago exhibit of last March. Being held under government auspices the display involved no cost to the exhibitors for space, light or heat and the large market promised by the government service attracted manufacturers from all directions, the articles exploited ranging from lead pencils to the most complicated forms of apparatus employed in office work. Good attendance was assured as government employees received tickets for the exposition and were granted leave for the purpose of attending and opportunities were afforded for their recommending such appliances as appealed especially to them. Of the hundreds of appliances shown, it is doubtful if there is a single one which would not find a useful place in any large office establishment. Exchange Professor in France. The exchange of proffssors recently arranged between Harvard University and the French Ministry of Public Instruction goes into effect next winter, with W. M. Davis (recently exchange professor in Berlin) as the first exchange professor in France. Prof. Davis wiII lecture on land forms. Prof. Diehl, of the SOl-bonne, will lecture on Byzantine history at Harvard.