preface to fifteenth edition

GENERAL INFORMATION, CONVERSION TABLES, AND MATHEMATICS 2.103
Rule I. The characteristic of any number greater than 1 is one less than the number of digits
before the decimal point.
Rule II.* The characteristic of a number less than 1 is found by subtracting from 9 the number
of ciphers between the decimal point and the first significant digit, and writing 10 after the result.
Thus the characteristic of log 936 is 2; the characteristic of log 9.36 is 0; of log 0.936 is 9 10;
of log 0.00936 is 7 10.
Mantissa of a Common Logarithm of a Number. An important consequence of the use of base
10 is that the mantissa of a number is independent of the position of the decimal point. Thus
93 600, 93.600, 0.000 936, all have the same mantissa. Hence in Tables of Common Logarithms
only mantissas are given. A five-place table gives the values of the mantissa correct to five places
of decimals.
Since it is possible to obtain logarithms by using hand calculators, this Handbook contains no
logarithm tables.
Helpful Hints
1. When connecting numbers to logarithms, use as many decimal places in the mantissa as there
are significant digits in the number.
2. When finding the antilogarithm, keep as many significant digits as there are decimal places in
the mantissa.
Examples: log 10.35 1.0149; antilog 0.065 1.16.
* Some writers use a dash over the characteristic to indicate a negative value; for example,
log 0.004657 7.6681 10 3.6681