To find the Diagonal of Any Square (or the Length of Brace ivhere the Ben is the Same Each Way). - Set 70 on B to 99 on A: find the diagonal on A above the length of side (or run, for braces) on B.

To find the Diameters or Circumferences of Circles. - Set 7 on B to 22 on A: then any number on A is the circumference of the circle whose diameter is immediately beneath, or vice versa.

Board Measure

Set the length in feet on B to 12 on A: find the number of square feet on B below the width in inches on A.

Areas Oe Circles

Set 7 on C to 3 on D: the area of any circle whose diameter is.on D is found just above, on C*

We have given only a small part of what may be done by the use of the slide-rule. We have given only that which would be of the most value to workmen. There are several works which are devoted entirely to explanations of the uses of the slide-rule, and any one desiring to pursue this subject farther would do well to obtain a copy. However, until one is very expert in the use of the slide-rule, it would be safer for him to figure out the problems he may have occasion to do.

* If tbe diameter is inches, the area will be square inches; and, if the diameter is feet, the area will be square feet.