Inventors do little harm in periodically making cheap aluminum or increasing its strength without adding to its gravity, but when a large corporation is started, as was done some months ago, with a lot of money and aluminum medals issued, the same being made out of copper, then the matter becomes serious. Probably, next to the hobby of separating water and creating enormous power thereby, the aluminum hobby holds undisputed sway. But as there really is something of interest to cyclists and cycle makers in the subject, there seems a need to touch upon it. Among the articles in the manufacture of which aluminum can be satisfactorily used we find in the catalogue of a well-known smelting firm mention made of bicycles, tricycles, etc. The idea exists in the minds of many that a bicycle made from pure aluminum would be a practical machine and much lighter than one of steel. This notion arises from the fact that aluminum in the pure state has a specific gravity of only 2.5, or about one-fourth the weight of steel. Below we print a letter from the Cowles Smelting and Aluminum Company on the subject. “+Lockport, N.Y., U.S.A.+, August 20, 1888. “+R. P. Scott+, Esq., Baltimore Md.: +Dear Sir+,—Replying to your favor of August 16, you can obtain the book on Aluminum, by Richards, from Philadelphia. Aluminum has a great many uses in its commercial state, but a simple pure aluminum casting has not sufficient strength to make it desirable for small parts. If you could have it rolled or hammered to shape, so as to make it rigid, it would become much more tenacious, but to secure strength desired in bicycle parts, your castings would necessarily be so large as to be ungainly, and we doubt if you would attain the most desirable end,—viz., light weight. The alloys of copper and aluminum are much better adapted to your requirements than the pure metal could possibly be. “Yours very truly, “+The Cowles E. S. and Al. Co.+ “_Tucker_.” It will be seen that the metal in its pure state lacks strength, and can only be used in the arts to any extent when alloyed with copper about in the proportion of nine of copper to one of aluminum. When alloyed as above, it is about as heavy as steel. AVERAGE ULTIMATE TENSILE STRENGTH OF METALS AND ALLOYS. (_From Trautwine’s Engineer’s Pocket Book_, 1885.) Pounds per square inch.