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A

TREATISE ON SURVEYING.

CHAPTER I.

ON THE NATURE AND USE OF LOGARITHMS.

SECTION I.

ON THE NATURE OF LOGARITHMS.

1. Definition. LOGARITHMS are a series of numbers, by the aid of which the operations of multiplication, division, the raising of powers, and the extraction of roots, may, respectively, be performed by addition, subtraction, multiplication, and division.

Such a series may be thus constructed. Above a geometric series, the first term of which is 1, place a corresponding arithmetic series, the first term of which is 0; thus:Arithmetical series, 0 1 2 3 4 5 6 7 8 Geometrical series, 1 2 4 8 16 32 64 32 64 128 256

To determine the product of any two terms of the geometric series, it is evidently only necessary to add the corresponding terms of the arithmetic series, and to notice the term of the geometric series agreeing to their sum; which term is the product required. Thus, to find the product of 4 and 32, we add the corresponding terms, 2 and 5, in the arithmetic series. Their sum, 7, corresponds to 128, the product required.

2. In a table of logarithms, the terms of the geometrical series are called the numbers; the ratio in this series is denominated the base of the table; and the terms of the arithmetical series are called the logarithms of the corresponding

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