BOOKS AND PAPER.

The terms, folio, quarto, octavo, duodecimo, &c., indicates the number of leaves into which a sheet of paper is folded.

2 leaves, is called, a folio.

METRIC SYSTEM OF WEIGHTS AND

MEASURES.

The primary base, in this system, for all denominations of weights and measures, is the one-ten-millionth part of the distance from the equator to the pole, measured on the earth's surface. It is called a METER, and is equal to 39.37 inches, very nearly.

The change from the base, in all the denominations, is according to the decimal scale of tens: that is, the units increase ten times, at each step, in the ascending scale, and decrease ten times, at each step, in the descending scale.

The names, in the ascending scale, are formed by prefixing to the base, Meter, the words, Deca (ten), Hecto (one hundred), Kilo (one thousand), Myria (ten thousand), from the Greek numerals; and in the descending scale, by prefixing Deci (tenth), Centi (hundredth), Milli (thousandth), from the Latin numerals.

Hence, the name of a unit indicates whether it is greater or less than the standard; and, also, how many times. The table is thus read:

Table of Equivalents.

Besides a clear apprehension of the length of the base, 1 meter, it is well to consider the length of the largest unit, the

Centimeter.

Millimeter.

myriameter, equal to nearly 6 and one-fourth miles; and also the length of the smallest unit, the millimeter, about four-hundredths of an inch. Compare, also, each of the smaller measures, the decimeter and centimeter, with the inch.

When, in the metric system, the value of any single unit is fixed in the mind, the values of all the others may be readily apprehended, since they always arise from multiplying or dividing by 10.

NOTE.-In all the tables, the UNIT is in small capitals, and should be constantly referred to.

Methods of Reading.

The number 25365.897 meters, is read, in English,

Twenty-five thousand three hundred and sixty-five meters, and 897 thousandths of a meter. But in the language of the metric system, it may be read,

Two myriameters, 5 kilometers, 3 hectometers, 6 decameters, 5 meters, 8 decimeters, 9 centimeters, and 7 millimeters. It may also be read, beginning with the lowest denomination, 7 millimeters, 9 centimeters, &c., &c.

In reading, remember that the unit of any place is ten times as great as the unit of the place next at the right, and onetenth of the unit of the place next at the left. Hence, the change from one unit to another, and the methods of reduction and reading, are identical with those in the system of decimal currency.

1. Write, numerate, and read, five hundred and ninety-six hectometers.

2. Write, numerate, and read, eighty-nine thousand and fortyone centimeters.

Questions.-What is the primary base of the metric system? To what portion of the earth's surface is it equal? What is its length? What is the ascending scale from the meter? What is the descending scale? What is the length of a myriameter? According to what law do the different units increase and decrease?

MEASURES OF SURFACES, OR SQUARE MEASURE.

Base, 1 Are

the square whose side is 10 meters.

= 119.6 square yards, nearly.

= 4 perches or square rods, nearly.

The unit of surface is a square whose side is 10 meters. It is called an ARE, and is equal to 100 square meters.

MEASURES OF VOLUMES.

Base, 1 liter = the cube or the decimeter.

61.023378 cubic inches.

= a little more than a wine quart.

Questions-What is the primary base of the measure for surfaces? To what is it equal, in square yards? What are the denominations, beginning with the least? To what is the centare equal? To what is the hectare equal?