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from week to week, a record is kept of each piece or class completed, and because he is exceptionally skilled on any particular piece, he is not kept upon that as stated. Were he speaking of an apprentice in a downtown shop he would have been perfectly correct.

In regard to the selling of the products being an imposition upon the student after he has paid his tuition, it seems to him to be a matter of opinion. He had never yet seen the student who was not proud that he could make an article that was fit to be sold instead of being dumped into the waste heap. He will do better work, take more interest, and consequently make more rapid progress when he feels that his product is to have a value in itself. Professor Carpenter speaks the mind of the student exactly when he says he likes to feel that he is making something useful and that his work is to be accepted in place of that of a more skilled mechanic.

There were a great many things that could be said in favor of this system if time permitted, but he would suggest to those who have had experience with the “model system” alone to visit the Worcester shops and see for themselves the advantages of a practical training.

THE HYDRAULIC LABORATORY OF THE MASSA

CHUSETTS INSTITUTE OF TECHNOLOGY.

By DWIGHT PORTER,
Associate Professor of Hydraulic Engineering.

This laboratory has been arranged and equipped upon an extensive scale for experimental researches and practical tests in hydraulics. The apparatus is used by the students of nearly all the engineering courses in regular laboratory exercises, during which they work in sections no larger than strictly necessary for conducting the particular experiment in hand. Such work is designed to give the students a practical demonstration of laws with which they have become familiar in a theoretical way only, to acquaint them with the appearance and behavior of certain standard forms of apparatus and to teach them the methods and precautions commonly necessary in hydraulic experiments. The time allotted to any one variety of work is what seems sufficient fairly to attain the above ends, and no more, it not being proposed in class exercises to make the young men adepts, nor in general, to achieve results of especial scientific importance. In connection with thesis work, or the studies of post-graduate students, special apparatus is every year devised and installed, suited to original investigations and to the securing of results of permanent interest and value.

The space devoted to the hydraulic laboratory covers about thirty by fifty feet on each of the two lower floors of the engineering building. The primary source of water supply is the city main, but it is rarely that draught is made directly upon this during an experiment, water being directly supplied from pumps, which in turn, draw from a large receiving pit sunk below the basement floor, the discharge from all experiments finding its way to the pit and thus being used over and over. Several pumps are in use, steam, rotary, and centrifugal, supplying the different apparatus. In order to secure a more constant pressure than that from the pumps, for certain kinds of experiments a ten-inch stand-pipe, eighty feet high, has been built, reaching to the top of the building. The supply to this from the pumps may be so regulated by valves and overflows, conveniently arranged on each floor, that the head shall be kept at any desired point during

experiment, with a fluctuation of scarcely one one-hundredth of a foot. Many of the pieces of apparatus have been so arranged that they can be run at will under pressure either from the stand-pipe or directly from the pumps.

An important feature of the plant is a closed steel tank, five feet in diameter and twenty-seven feet high, extending from the basement floor upward through two stories. It is connected at top and at bottom with the stand-pipe previously mentioned, and at four points on each floor is arranged for the insertion of orifices, free or submerged, mouth-pieces and other fittings, and for connections with motors and experimental pipes.

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It is fitted with hydraulic gates so planned that an orifice, for example, may be quickly exchanged for another without the necessity of drawing down the water in the tank.

For certain experiments on the flow of water through pipes, three lines of three-inch pipe have been erected. One of these is of iron, with a Venturi meter inserted in its course; the other two are of brass, very carefully made, with piezometer connections of approved form at sundry points. One of the brass pipes is arranged for the insertion of diaphragms with orifices of various sizes; and the other for the insertion of short experimental pieces of pipe provided with side orifices, branches or other devices. The discharge from the various pipe lines passes finally through a hose nozzle, with pressure-gauge connection to be used in determining the coefficient of discharge. The nozzle discharges into a movable double chute, through one branch of which the flow may be wasted until it is desired to begin an experiment, when the other branch may instantly be thrown into the path of the jet, and the water directed through the floor into a measuring tank beneath.

For delicate observations upon the velocity at any given point in flowing water, the laboratory contains three different instruments embodying the principle of the Pitot tube. Two of these, for use respectively in jets from nozzles and in streams flowing under pressure through pipes, are the property of Mr. John R. Freeman, by whom they have kindly been placed at the command of the institute. The third, for jets from standard orifices, has been designed especially to use on the large tank which has been described. In each case, the pressure of the flowing water due to its velocity is transmitted through a minute orifice and a connecting tube to a mercury gauge, the reading of which indicates the velocity at the tip of the tube. A simple attachment to the last mentioned of these devices has permitted measuring the shape of the jet and the size of the contracted vein with the greatest nicety.

For measuring the quantity of water discharged during experiments, the common method employed is that of weighing, the temperature of the water being at the same time observed. Thus, in determining the co-efficient of discharge of standard orifices, the flow from the orifice passes into a large cask, with ample discharge pipe and quick-acting valve at the bottom, and thence into another and similar cask underneath, resting directly upon scales. The upper cask serves for temporary storage while the contents of the lower one are being weighed and discharged. By this means, with casks of moderate size, it is not difficult to weigh continuously at the rate of forty thousand or fifty thousand pounds of water per hour. Again, the discharge from experiments on the second floor may be diverted through chutes to any one of several measuring devices on the floor below. One of the most important of these is a cylindrical steel tank, six feet in diameter and ten feet high, capable of holding some two hundred and eighty cubic feet of water. This tank is conveniently placed for drawing off and weighing the contents, and is by this means calibrated. In order to determine the

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