and in others it is perhaps due to a lack of proper time; but whatever the cause may be, failure to secure good claims is a misfortune so far as the patentee is concerned. A writer in The Forum, referring to the difficulty of claim writing, has said: "It takes a very experienced hand to avoid defects which will nullify the patentee's proper advantage. An omission is fatal; an addition is fatal; and a vagueness is fatal." Broadly considered, the claims of an application may be divided into generic and specific claims. If the invention disclosed in an application will support a broad or generic claim, such a claim should by all means be included. But in addition to such claim, specific claims also should be included because it is very much easier to anticipate a broad claim in the prior art than it is to anticipate a specific claim, and it may happen, if the claims of the patent are ever subjected to litigation, that the patentee would be able to sustain the validity of the specific claim but would be unable to sustain the validity of the generic claim. In such case, the patent, by reason of the presence of the specific claim, would still be of value to the patentee, while, on the contrary, if it had included only the generic or broad claim or claims, which had been anticipated, the value of the patent would be entirely destroyed. It is not always so, but, generally speaking, a broad claim includes a small number of elements in combination, while a specific claim will include a greater number of elements in combination, and these elements may be still further affected and narrowed by qualifying limitations. It sometimes happens that an inventor, who fully understands the details and principles of his invention, concludes that he is better fitted to write his specification and claims, that is to say, is better fitted to prepare his application for the Patent Office than some one who has had experience in the writing of specifications and the drawing of claims, and therefore undertakes to do this work. It is very unusual to find an inventor who has had sufficient experience to prepare the specification and claims of an application properly, and the chances are about one hundred to one against his succeeding in drawing claims which adequately protect his invention. After the application has been placed in condition for allowance, it is allowed by the examiner, after which it goes to the Issue Division of the Patent Office. Then, upon the payment of the final fee of $20, the patent is printed, the grant is prepared and is signed by the Commissioner of Patents, and the patent is issued under the seal of the Patent Office. Many inventors suppose that when they have secured their patents their troubles are over, but the fact is that if the invention is of any considerable value or worth, the patentee will be beset by a horde of infringers who will attempt to use the invention and secure the benefit of the inventor's thought and ingenuity. The patentee can protect his rights only by bringing and prosecuting a suit in the Federal Courts and securing an injunction against infringers. It seems strange that a person who would not think of trespassing upon the real property of another person, or who would not think of interfering with ordinary chattel property belonging to a stranger, will not hesitate to trespass upon the patented property of another, whenever it appears to him that such trespassing would inure to his advantage, considered from a business and financial standpoint. Notwithstanding the fact that patented property is constantly being subjected to the attacks of infringers, such property is very valuable, and, as has already been pointed out, constitutes the basis of investment of many millions of dollars in the United States, and it has been asserted in a comparatively recent annual report of one of the Commissioners of Patents "that we mainly owe to our patent system such foothold as we have gained during the past fifty years in foreign lands for our manufactured products." AN 8-FOOT STEEL CHIMNEY, 230 feet in height, has just been completed and will be erected in Mexico. This will be the highest steel chimney in America. Mechanical and Engineering Section. Stated Meeting, held Thursday, December 1, 1904. Physical Characteristics of Certain Bronzes for BY STRICKLAND L. KNEASS, Member of the Institute. It is not necessary for the purpose of the present paper to touch upon the history of the bronze alloys, the use of which reaches far back to the dawn of civilization. A vast amount of research has already been given to the subject, and the early methods employed in their production have been entirely superseded, so that even an accurate description would have but little practical value to the modern metallurgist or manufacturer. The copper-tin alloys in general use vary from 5 to 24 parts by weight of copper to I of tin, with a small percentage of either zinc or lead or of both elements. The true binary has a comparatively small part to play in the arts and trades compared with the total amount of bronze in use, because the cost and difficulty of tooling and machining is much greater, and lead, zinc, nickel, phosphorus or aluminum are almost always introduced, producing a beneficial effect upon the physical characteristics. For example, a trace of zinc is used in a 5 to 1 mixture for certain kinds of spindle-bearings or sleeve nuts, producing a metal hard and brittle, having a whitish-gray fracture, machining with a short chip which flies from the tool with great force; care is required to obtain a good smooth surface, but when obtained the bearing wears well under heavy pressures. A ratio of 7 of copper to 1 of tin, and a little more zinc, makes a good hydraulic bronze, with sufficiently high tensile strength for all ordinary purposes, machining well and running solid in the mold, even with large size sections. Commencing with pure tin and passing through the various proportions of copper until the latter metal is reached, VOL. CLIX. No. 949, 5 the appearance of the fracture changes from white, through gray, ash-gray, bluish-red, reddish-yellow to the tile-red of pure copper. The melting point changes at the same time with each increment of copper, until that of the latter metal is reached. According to Mallet, the maximum density of the alloy is somewhat above that of copper, and occurs when the proportions by weight are about 3 of copper to I of tin. The chemical union of copper and tin in more than one or two proportions is disputed by many authorities, although the statement has been made before this Institute, that I to I, I to 2, I to 3 and 1 to 4 are probably alloys.* Be this as it may, in the actual behavior of the binary alloy in the foundry, owing to imperfect mixing or to other reasons, there is almost always found a certain amount of liquation and a proportion of eutectic alloy which affect the physical characteristics. This subsidiary alloy is much more in evidence, and its presence and amount of greater importance in the quaternary alloys or mixtures of copper, tin, lead and zinc, with which we have to deal in this discussion. Here there is always liquation, depending upon the form and size of the section and the rapidity of cooling. For this reason, great care is required to obtain a perfectly homogeneous mixture, approaching as nearly as possible a chemical alloy, free from microscopic pin holes due to shrinkage or to occluded gases, and without the harder spots or lumps of eutectic alloy of the constituent metals. This is where the skill and care of the foundryman, designer and molder, as well as the composition of the metal, play an important part. The rapidity of melting, temperature of pouring and the condition of the mold itself, all affecting the results. The essential characteristics of a good steam metal are, homogeneity, solidity, tensile strength, rigidity, facility for machining, fluidity in casting, and non corrosiveness, all being supplied by the various mixtures of bronze in use in * See this Journal, 199, 26. Art. Outerbridge, Microstructure of Bronzes. varying degrees of excellence. With reference to the composition it may be said in general that homogeneity depends upon the causes already cited; tensile strength and rigidity upon the proportion of copper to tin and their preponderance over the lead and zinc, while the form and character of the chip is determined chiefly by the percentage of lead and fluidity by the zinc. The proper mixture for any desired purpose must, therefore, be a compromise, with a fixed tendency toward homogeneity and density, and it is not an easy matter to obtain the desired results in foundry work without careful attention to detail and consistent experiment. And experimental work should not be limited to the examination of etched sections, nor should conclusions be drawn from one set of castings. Specific gravity tests and microscopic examinations are also necessary to cover the field satisfactorily, and are of as much importance in the examination of the physical properties of bronze steam metals, as of iron or steel, and such tests should be repeated at periodic intervals to determine the regularity of product of the foundry. Bronze castings, both finished and unfinished, are subjected in service to two serious deteriotating agencies, namely, the attrition and the solvent action of the contained fluids. These effects are scarcely noticeable on the rough casting, surfaced as received from the mold or after sub. jection to the sand blast or cleaning bath, but finished surfaces are often seriously affected. The same result that is obtained in the laboratory by etching polished sections, occurs in practice on an exposed valve or seat, except that the final result is not so satisfactory; the more soluble metals or alloys are dissolved by the acidulous or alkaline solution, leaving the more resisting and harder eutectic. alloy to protrude above the surfaces, preventing continuous contact between the valve faces. Further, the high velocity of the fluid passing through a throttled valve, cuts out the softer parts and a bad leak and defective seat soon result. The porosity of the casting deserves serious consideration, even though the openings be not visible to the naked |