“It works well, casts well, holds a fine surface under the tool and when exposed to the weather, _and it is in every respect considered the best bronze yet known_. Its _high cost alone has prevented its extensive use in the arts_. These alloys are very uniform in character and work regularly and smoothly. Even one per cent. of aluminum added to copper causes a considerable increase in ductility and fusibility, and enables it to be used satisfactorily in making castings. Two per cent. gives a mixture used for castings which are to be worked with a chisel. It is softened by sudden cooling from a red heat. Its coefficient of expansion is small at ordinary temperatures. “It has great elasticity when made into springs; it has been found useful for watches, and has the decided advantage over steel of being little liable to oxidization. Kettles of aluminum bronze are used in making fruit syrups and preserves. Steel containing but .08 per cent. of aluminum is said to be greatly improved by its presence.” Aluminum bronze, such as would be required for cycle castings, costs from thirty to fifty cents per pound, according to quality and quantity. A valuable alloy of aluminum and iron has recently been made, by which it is maintained that wrought-iron castings are possible. The factory is, I believe, at Worcester, Mass. In our endeavor to learn more upon the subject we have been referred to the United States Mitis Co., No. 26 Broadway, New York, which company has the exclusive right in this country to make Mitis castings, or of granting permission to those who desire to make these castings themselves. STRENGTH OF TUBES. Metal in the form of tubes resists all strain liable to occur in cycle work better than in any other form. In regard to strain of compression, we find, in “Wood’s Resistance of Materials,” the following summary: “Experiments heretofore made do not indicate a specific law of resistance to buckling, but the following general facts appear to be established: The resistance of buckling is always less than that of crushing, and is nearly independent of the length. Cylindrical tubes are strongest, and next in order are square tubes, and then +-------+ the rectangular. Rectangular tubes | | are not so strong as +-------+ +---+---+ tubes of this form | | |.” +---+---+ There is, however, very little direct crushing strain on the tubes in a cycle; it is almost entirely a strain of flexure or bending; hence this is the only interesting feature pertaining to the subject in cycling work. Since a tube is stronger than a solid bar, for same weight the intuitive idea is to make the tube as large as possible, and the mathematical demonstration which we append shows this to be correct, generally speaking.