of oil were put into a dynamometer, which was run at 35 miles an hour, until the temperature was raised from 60° to 200° Fah. The exact number of revolutions necessary to produce this change of temperature was noted in each case, and is given in the last column of the following table.

It has lately been demonstrated that natural petroleum oils, when thoroughly freed from grit, are for many purposes as good, if not better, than sperm, with the advantage of being much cheaper; but they are objectionable in consequence of their liability to stain bright work or finished machinery.

It is not by any means uncommon to see ignorant and inexperienced persons who have charge of steam-engines pouring oil on cross-head guides and piston-rods every five minutes during the day. This is immediately rubbed off by the shoes or the piston-rod packing, without rendering any service, which is a wilful waste of the necessary supplies in their charge, and has a tendency to lessen the profits of the establishment.

Questions:

THE ANSWERS TO WHICH WILL BE FOUND IN THE TEXT.

What are the objects and functions of the bed-plate as a part of the steam-engine?

Give the rule for finding the necessary strength of a bed-plate for any given speed and pressure.

State the rule for finding the proper thickness of a steam-cylinder of any diameter.

Give the rule for finding the diameter of a cylinder for any given horse-power.

Give the rule for finding the cubic contents of a steam-cylinder of any given diameter.

State the rule for finding the quantity of steam that any engine will use at each stroke of the piston.

Give the necessary strength of cylinder-head bolts.

What are the objects and functions of the pistons of steamengines, and what qualities should they possess?

Give the proportions of piston-rods for condensing and noncondensing engines, according to the best modern practice.

Give the units of horse-power for various piston speeds.

Give the proportions of steam- and exhaust-pipes according to the best modern practice.

What proportion should the diameter of the valve-rod bear to that of the cylinder?

Give the proper length and width of the cross-head bearings. What is the meaning of the term eccentric?

What are the functions of the crank, and what change of motion does it induce?

Explain the cause of the variation of the piston in the cylinders of steam-engines when their cranks are at half-stroke.

Give the rule for finding the position of the piston in the cylinder when the crank is at half-stroke.

Is there any loss of power incurred in the employment of a crank as a mechanical device for converting reciprocating into rotary motion?

Give the rule for finding the necessary proportions of crankpins for any engine.

Give the proportion of the crank-shaft and main-bearings according to the best modern practice.

Give the proper proportions of gibs, keys, and straps for any engine.

Why is the strap thicker at the slot than at the part which encircles the box?

What are the functions of the link?

What is the meaning of the term "radius of the link ”?

Describe the mechanism of the various links employed as a reversing-gear for steam-engines.

What is the object of the fly-wheel?

Give the rule for finding the proper weight of fly-wheel for any engine, speed and pressure being given.

What are the functions of the steam-engine governor?

Give the rule for finding the proper size of governor-pulleys.

Give the most approved method of counterbalancing the reciprocating parts of steam-engines.

What are the most common causes of heating in the journals of steam-engines?

What are the uses and functions of the slide-valve?

Explain the advantages and disadvantages of the slide-valve as contrasted with those of other forms.

Explain the action of poppet- or conical-valves.

What are the meanings of the terms lap and lead on the valve? What is the meaning of the term loss of lead?

What is meant by the terms valve-seat and valve-face?

Explain the meaning of the terms valve-circle and valve-stroke.

How would you proceed to ascertain the amount of lap and lead on a slide-valve without opening the steam-chest?

Give the meaning of the term cut-off, and the amount of lap required to cut-off at different points of the stroke.

State the most economical point in the stroke at which to cut off the steam, and demonstrate it by an example.

What is meant by friction when applied to slide-valves?

How would you proceed to set the valves of a steam-engine?

Is the friction of a perfectly fitting slide-valve more or less than that of an imperfectly fitting one?

Give the names of the different valves and valve-gear employed for the admission and escape of the steam to and from the cylinders of steam-engines.

Give the technical terms as applied to the valve-gear of steamengines.

Give the names of the various valves and cocks in use on different steam-engines and boilers.

Give the names of the various pipes in connection with different kinds of steam-engines.

Explain the meaning of the term valve-gear.

In what condition should an engine be kept?

What is the best evidence of an engineer's capabilities?

What dependence should be placed on patent oil-cups?

In what condition should the packing in the piston- and valverod boxes be kept?

What is the objection to striking any part of an engine with the face of a hammer or head of a monkey-wrench?

What is the objection to placing piston-rod packing or cotton waste on the floor?

When should piston- and valve-rod packing be applied?

In what manner may piston- and valve-rod packing be improved?

How should gum-joints be treated, which must of necessity be frequently broken?

What precaution should an engineer take, when it becomes necessary to stop an engine with a heavy fire in the furnace?

How should the cylinder drip-cocks be kept, when an engine is stopped?

When should the tallow or any other lubricant be admitted to the cylinder?