96. The weight of a ball of cast-iron, 9 inches in diameter, is 100.37 pounds; what must be the diameter of a leaden ball of equal weight?

Specific gravity of cast-iron 7.207

66

66 lead

hence 7207: 93: 11.352 466 =

ameter.

=

97. What are the general laws of fluids in regard to weight and pressure?

The weight of a fluid is as the quantity, but. the pressure exerted is as the vertical height; hence, any vessel containing a fluid sustains a pressure equal to as many times the weight of the column of greatest height of that fluid, as the area of the vessel is to the transverse sectional area of the column.

98. If a conical vessel whose vertical height is 3 feet, and the diameter of its base 2 feet, be placed upon the ground, and filled with fresh water, what will be the pressure on the base in pounds?

Weight of a column of fresh water, 1 inch diameter, and 1 foot in height =.341 pounds, and 242 576, hence 341 × 576 589.248 pounds.

=

=

99. Each side of a cubical iron tank in which tallow is kept, measures 351⁄2 inches; required to know the number of pounds remaining, when at 18 inches in depth-the tallow having been heated sufficient to render it compact as one solid mass.

Specific gravity of tallow =

inch.034 pounds.

=

942

1 cubic

Hence, 35.5 x 35.5 1260.25 square inches. And 1260-25 x .034 x 18 = 771-27 pounds.

100. A similar tank, with 23 inches of oil in depth; how many imperial gallons?

An imperial gallon =277.274 cubic inches - 1 .003607.

cubic inch =

Hence, 1260-25 x .003607 x 23 = 104.55 gallons.

101. Because of the weight of paddle-wheels in steam-vessels, and the difficulty of properly lubricating the outer end of paddle-shafts, the bearings frequently wear down, and consequently the shafts become not in one direct line; now, when such takes place, how is the proper thickness of lining obtained, or how much must the outer end of shaft

be raised, so that the shafts may again be brought to their proper lineable position ?

Set the engine either at top or bottom stroke; measure the distance between the cranks as near the extremity of length as convenience will admit; turn the engine round to the other extremity of stroke, and then at the same point on the crank take also their distance. Obtain the length of paddle-shaft from face of crank to outer bearing, also the length of crank from centre to that point on its face where their distance between was taken; then say, as the distance from centre of crank-shaft to point where the distance between cranks has been taken, is to the difference of distances between the cranks at top and bottom strokes, so is the length of paddle-shaft to half the thickness of lining required.

Ex. Suppose the length of a paddle-shaft from face of crank to face of outer bearing equal 16 feet 3 inches, and the length on face of crank from centre of shaft to where the distance between cranks was taken equal 2 feet 8 inches, the difference of distance between crank at top and bottom three-eighths of an inch, what is the outer end of shaft down, and what thickness of

liner will be required under the brass, so as to

bring the shafts in a direct line?

16 feet 3 inches

inches = 32 inches.

195 inches, and 2 feet 8

Hence, 32: 37.5 : : 195 : 1.676 ÷ 2 = .838 inches.

102. What is meant by proper lubrication? By proper lubrication is implied a sufficient supply of unguent matter to a revolving or otherwise moving body, whereby to diminish friction, and prevent abrasion by interposition between the moving and stationary surfaces.

103. What are the common known laws of friction?

1. When no unguent is interposed, the friction of any two surfaces (whether of quiescence or of motion) is directly proportional to the force with which they are pressed perpendicularly together; so that for any two given surfaces of contact there is a constant ratio of the friction to the perpendicular pressure of the surface upon the other.

2. When no unguent is interposed, the amount

of the friction is, in every case, wholly independent of the extent of the surfaces of contact; so that the force with which two surfaces are pressed together being the same, their friction is the same, whatever may be the extent of their surfaces of contact.

3. That the friction of motion is wholly independent of the velocity of the motion.

4. That where unguents are interposed, the amount of friction depends more upon the nature of the unguent, and upon the greater or less abundance of the supply, than upon that of the surfaces in contact. It has been ascertained by experiments, that with a continuous, interposed stratum of hog's-lard and olive-oil, between wood and wood, metal on wood, and metal on metal, in motion, the amount of friction is nearly an equal quantity; but to render an unguent of proper efficiency, the nature of such substances used must be measured by the pressure or weight tending to force those surfaces together.

104. When, by any mode of measure, it is ascertained that, for condensation of steam, an engine requires 93 gallons of water per minute, the num