FORMERLY School of Mines Preparatory School. 417 Madison Avenue, Between 48th and 49th Streets, NEW YORK CITY Twenty-fifth Year Begins October 1st, 1906. THE THE school is well equipped with physical and chemical laboratories, in which the students are required to perform a complete set of experiments illustrative of their recitations in physics and general chemistry. A special laboratory is devoted to qualitative chemical analysis for advanced students. Five hundred Students of Columbia School of Mines have been instructed in the Woodbridge School. Also a large number have been prepared for Massachusetts Institute of Technology, Stevens Institute, Sheffield Scientific School, Lawrence Scien ific School, Troy Polytechnic Institute, Cornell University, and the Classical, Medical, and Law Departments of Harvard, Yale, Columbia and Princeton. A summer school for students who have failed in June begins August 13th and coaches men for the Fall examinations. All classes are limited to five. College men are coached in Freshman and Sophomore Mathematics and Quantitative Analysis. Geology of Pioche, Nevada, and Vicinity. By Fred. J. Pack... 285 The Historical Development of General Chemistry. By Wilhelm 313 The Determination of Minerals in Crushed Fragments by Means of the Polarizing Microscope. By Austin F. Rogers... 340 Registered at the New York Post Office as Second Class Matter. TWO DOLLARS PER YEAR. FIFTY CENTS PER NUMBER. BURNHAM, WILLIAMS & CO., PHILADELPHIA, PA., U. S. A. LOCOMOTIVES OF EVERY DESCRIPTION Electric Locomotives built in conjunction with Westinghouse Electric and STANDARD STEEL WORKS HARRISON BUILDING, PHILADELPHIA, PA. Steel Tired Wheels Solid Forged Rolled Steel Wheels Locomotive Tires Forgings Railway Springs Castings BEST QUALITY AND GREATEST EFFICIENCY GUARANTEED THEREFORE, MORSE TOOLS ARE THE MOST ECONOMICAL MORSE TWIST DRILL AND MACHINE CO. NEW BEDFORD, MASS., U. S. A. We make and carry in stock various styles of Arbors. Reamers, Chucks, Counterbores, Countersinks, Dies, Three and Four Groove Drills, Drills with Oil Holes, Jobbers' Drills, Letter Drills, Wire Drills, Gauges, Mandrels, Metal Slitting Saws, Cutters with Solid and Inserted Teeth-Axial, Radial, Angular, Form and Gang Cutters; a full line of Taps, Adjustable Tap Wrenches, Opticians', o del Makers' and Machinists' Screw Plates and Dies, Solid Pipe Dies and Solid Machine or Bolt Dies, Tools for Turret Head Machines and many others; being made, as are all of our tools, of the best material and by the best workmen, their accuracy and effectiveness are assured. Hydraulic Dredge discharging through 6.170 tt. of pipe. SPECIALTIES: Dredging, Dredging Machines, Land Reclamation, Docks, Piers, Foundations, Bridges. MAIN OFFICE: PARK ROW BUILDING, NEW YORK. BRANCH OFFICES: 220 MARKET STREET, SAN FRANCISCO, CAL. MANILA, PHILIPPINE ISLANDS. 95 YESLER WAY, SEATTLE, WASH. To obtain the full advantages of an isolated plant, it is essential that each piece of apparatus installed shall be the most suitable for the conditions under which it will have to work and that the plant when considered as a whole will be capable of manipulation and operation in such manner as to produce a maximum efficiency at all times and require a minimum of labor for operation and maintenance. To accomplish this the entire plant must be analyzed from the delivery of the fuel, to the supply of current at the switchboard. It is not sufficient to follow the pattern of some other plant which is supposed to be operating satisfactorily, and make the necessary changes in size of units to suit the load conditions. A careful study must be made of the functions which it is intended that the plant shall perform and the type of plant which will be best suited to perform these duties in the most efficient and economical manner. The first and most important question which must be decided is that of the type of prime mover to be employed. Until very recent years the commercial limitations were such as to present, what may now be considered, but few types from which to select. The plant in which the prime mover was other than the reciprocating steam engine was a distinctive exception, therefore few cared to give much consideration to the internal combustion engine using gas or oil or to the steam turbine. Hence so far as the power producing apparatus in the plant was concerned, the questions which were at that time of prime impor tance, were whether the expansion in the steam engine should be single or compound, whether a condenser should be used, and what would be the most suitable pressure under which to operate. This state of affairs does not exist to-day as the internal combustion engine has been brought forward as a prime mover and its improved economy in fuel consumption over that of the reciprocating steam engine, justifies its recognition and consideration. For commercial use the internal combustion oil engine has not been developed in the same way that has the gas engine and except in the case of the small units and in a few special instances, its use has not thus far received the consideration which must be given the latter. The lack of uniform angular velocity and the uncertainty in action and high maintenance cost were objections to the use of internal combustion engines for electrical purposes which recent developments have removed. Their inability to carry heavy overloads, however, together with the fact that their range of economical load is practically limited to between 50 per cent. load and full load, are defects which thus far have not been satisfactorily eliminated and which would be decided draw-backs in many plants. The question of speed regulation of these engines at light loads must also be considered when parallel operation is contemplated. These difficulties may, perhaps, be best overcome by the installation of a storage battery plant to take the fluctuations in the load on the station, when direct currents are employed, but this is not always desirable or commercially practicable, and would usually add considerably in the first cost of the generating plant. In sections of the country where cheap gas can be obtained the gas engine will show a much greater economy than any of its competitors, and recent improvements in gas producer and supply apparatus have brought the first cost of installation of gas plant equipments down to a point where it compares favorably with that of first-class steam plants using reciprocating engines. The delay in the development and use of the gas engine has been largely due to the difficulty of making all elements of the engine and gas generating apparatus reliable in operation and to the absence of an efficient and inexpensive gas producing apparatus. The introduction of the steam turbine has worked greater changes in the power plant design than any other item. It has |