Of Specific Gravities.

EXAMPLES.

1. A piece of elm weighs 15 lbs. in open air. A piece of copper which weighs 18 lbs. in air and 16 in water is attached to it, and the compound weighs 6 lbs. in water: what is the specific gravity of the elm?

Then, as 25 15 1000 600, which is the specific gravity of the elm.

2. A piece of cork weighs 20 lbs. in air, and a piece of granite weighs 120 lbs. in air, and 80 lbs. in water. When the granite is attached to the cork the compound mass weighs 163 lbs. in water : what is the specific gravity of the cork?

Ans. 240.

PROBLEM III.

To find the specific gravity of fluids.

RULE.

1st. Weigh any body whose specific gravity is known, both in the open air, and in the fluid, and take the difference, which is the loss of weight.

Of Specific Gravities.

2d. Then say, as the true weight is to the loss of weight, so is the specific gravity of the solid, to the specific gravity of the fluid.

EXAMPLES.

1. A piece of iron weighs 298,1 ounces in the air, and 259,1 ounces in a fluid, the specific gravity of the iron is 7645: what is the specific gravity of the fluid ? First, 298,1-259,1=39 loss of weight:

Then, 298,1 39: 7645: 1000, which is the specific gravity of the fluid: hence the fluid is water.

2. A piece of lignumvita weighs 423 ounces in a fluid, and 1663 ounces out of it; what is the specific gravity of the fluid that of lignumvita being 1333?

Ans. 991, which shows the fluid to be liquid turpentine or Burgundy wine.

NOTE. In a similar manner the specific gravities of all liquids may be found from the following table.

REMARK.-In the table of specific gravities, the cubic foot of water, which weighs 1000 ounces, is taken as the standard, and the figures in the column of specific gravity shows the weight of a cubic foot in ounces, or how many times each substance is heavier or lighter than water. The other column shows the weight in ounces of a cubic inch, or the weight in pounds of a cubic foot.

PROBLEM IV.

The specific gravity and weight of a body being given, to find its solidity.

Of Specific Gravities.

RULE.

As the tabular specific gravity of the body is to its weight in ounces avoirdupois, so is 1 cubic foot, to the content in cubic feet.

EXAMPLES.

1. What is the solid content of a block of marble, that weighs 10 tons, its specific gravity being 2742.

First, 10 tons=358400 ounces.

:

Then, 2742 358400 1: 130, which is the content in cubic feet?

NOTE. If the answer is to be found in cubic inches, multiply the ounces by 1728.

2. How many cubic inches in an irregular block of marble, which weighs 112 pounds, allowing its specific gravity to be 2520 ?

3. How many cubic inches of gunpowder are there in 1 pound weight, its specific gravity being 1745?

Ans. 15, nearly.

4. How many cubic feet are there in a ton weight, of dry oak, its specific gravity being 925.

THE END.

Ans. 381.