be of most service to the student. The student, having made an earnest effort to produce these papers, is in touch with the subject; and the instructor, by question or suggestion, is able to draw him out and aid him in seeing many things which had entirely escaped him previously. It is here that the enthusiastic, sympathetic, tactful teacher can be of great value、 to the student in assisting him to discover new facts without in any way destroying his initiative.

The credits to be given for laboratory work should be determined very largely by the thoroughness with which the reports are required to be prepared. The report is the best indication of the student's interpretive ability. It should be written in a clear, concise manner, and should be carefully corrected both with respect to the English and the subject matter contained.

In the electrical laboratory of the University of Wisconsin, one unit of credit is given for one and a half hours' work in the laboratory per week, the reports to be written up on outside time. This amounts to allowing as much time for the writing and correcting of reports as is used in performing the experimental work. This allows time for careful consideration and complete calculations of the data obtained in the laboratory.

I have referred to assignments for graduate students. Men who have reached this point in their study should be encouraged to follow out new developments and analyze their results carefully, looking to the discovery of new information, or to finding new applications for principles already known.

In conclusion, I would say that with able, tactful instructors and equipment carefully selected for use, the student being held responsible for apparatus in his charge, the engineering laboratory is one of the most important factors in producing the fertile graduate of to-day and the able engineer of to-morrow.

CENTRAL STATION DESIGN.

BY ALBERT A. RADTKE,

Professor of Electrical Engineering, Armour Institute of Technology.

Central station design is one of the courses given in technical schools for the purpose of correlating the theoretical training with its practical application. The difficulty in developing this power of correlating which insures to a great extent the success of the student in practice, is due mainly to the small amount of time that can be allotted to such courses, and it was in recognition of this difficulty that the writer developed the method here described which during the three years of its application at the Armour Institute of Technology has produced gratifying results.

At Armour Institute, as in most technical schools, this course is scheduled for the senior year in which it is allowed seventy-two hours in periods of six hours each. It is preceded by a course in the junior year which covers the principles underlying the steam equipment of a power plant and which is accompanied by numerous problems in the calculation and design of individual apparatus such as condensers, pumps, feed water heaters, and similar machinery.

At the close of this course each student, or group of students, is given a special assignment which is to be the basis of the work in central station design, and which consists of data on a system for which he is to design a plant. These data include the location and the size of the system, the character and distribu

tion of the load, the coal and water facilities of the location, the kind of fuel available, its calorific value and cost, the rate of increase of the load and a loadcurve showing the day of maximum output for the preceding year. These data are secured directly from central station managers operating systems in the middle-west by sending out blanks accompanied by a letter explaining the purpose and asking for their cooperation.

With this as a basis the student prepares a preliminary layout of his plant and calculations for his design. This is then gone over with the instructor, and a decision is made on the apparatus for his plant; also the type of system whether single or multiphase, the frequency and voltage, etc. The student then prepares a list of the apparatus needed for its equipment which is brought to the instructor. He is then supplied with templates of standard apparatus and machinery which fit his needs from the files of the department.

The student arranges these templates on his drafting board and when he has secured a practical and proper arrangement, pastes them in place on his detail paper and draws in the piping, breeching, stacks, etc., and building.

The number of drawings required of each plant are five:

A plan, "-1 ft.

A sectional elevation, "-1 ft.

A wiring diagram, no scale.

A front and sectional elevation of switchboard, 11"-1 ft.

A piping plan, 1"-1 ft.

In addition to handing in the required drawing at the completion of the term, he tabulates the calculation of apparatus and writes a discussion of the reasons why the various types of machines were chosen.

The templates have been made from blue prints secured from manufacturers of standard apparatus and machinery. These blue prints are then reduced to the " to 1 ft. scale either by the students or draftsmen and traced on tracing cloth. By this method there has now been collected a fairly complete series of templates of the standard machines. They include:

Prime movers, sizes up to 1500 kw.:

Steam engines;

Steam turbines; Curtis, Parsons.

Gas engines; Allis-Chalmers, Westinghouse.
Water turbines.

Condensers:

Jet and surface; Wheeler, Worthington, Alberger, Baragwanath.

Pumps:

Air, circulating, boiler feed; Dean, Blake, Worthington.

Boilers, all sizes up to 550 h.p.:

Water tube; B. & W., Heine, Parker.

Exciter-sets, sizes up to 100 kw.:

Steam-driven, motor-driven.

Mechanical stokers and chain grates:

B. & W., Jones underfeed, Mackenzie, Roney.

Steam traps:

For all sizes of pipes.