Shrinkage of Castings.

In making all patterns of work, we make an allowance of inch larger per foot in cast iron; for brass allow full.

SPRING STEEL.

I give the following result of experiment made by me with spring steel. The bar made use of was supported on both extremities, and the weight suspended in the middle. The following are the results:-Length between the fulcrum 2 feet; width of bar 1 inch.

The table shows that the deflection was equal in both cases. At the same time it appears that the squares of the thickness are to each other as the bending weights, 2 very near, thus conform82 3 118 ing to the general theory.

For calculating the Radius of a Curve when the Angle of Deflection and Chord are given.

Railroad curves are always laid off with chords of 100 feet, and we often find, when speaking of

curves, the angle of deflection is merely given. Now to find the radius:

5730 feet are a common radius, which is equal to a deflection of 1°.

RULE.-Divide the number of degrees deflected into 5730; the product will be the radius of the

curve.

EXAMPLE.-We have a curve`with a deflection of 6o, and the chord 100 feet.

6)5730

955 feet radius of curve, Ans.

TABLE of Revolutions, per Mile, of Driving Wheels, and con sumption of Steam, Water, and Fuel, for each sized Wheel; taking the Steam admitted to each Cylinder as exactly one cubic foot at a gross pressure of 114·7 lbs., or 100 lbs. on the spring balance.

Power is compounded of the weight or expansive force of a moving body multiplied into its velocity.

THE power of a body which weighs 40 lbs., and moves with the velocity of 50 feet in a second, is the same as that of another body which weighs 80 lbs., and moves with the velocity of 25 feet in a

second; for the products of the respective weights and velocities are the same.

40 x 50 2000; and 80 x 25 = 2000.

Power cannot be increased by mechanical means.

Power is applied to mechanical purposes by the lever, wheel and axle, pulley, inclined plane, wedge, and screw, which are the simple elements of all machines.

The whole theory of these elements consists simply in causing the weight which is to be raised, to pass through a greater or a less space than the power which raises it; for, as power is compounded of the weight or mass of a moving body multiplied into its velocity, a weight passing through a certain space may be made to raise, through a less space, a weight heavier than itself.

Power is gained at the expense of space, by the lever, the wheel and axle, the pulley, the inclined plane, the wedge, and the screw.

LEVER.

Case 1.- When the fulcrum of the lever is between the power and the weight.

RULE.-Divide the weight to be raised by the power to be applied; the quotient will give the difference of leverage necessary to support the weight in equilibrio. Hence, a small addition either of