Fig. 99 represents a scale of degrees, which is found on several draughting implements. To use this scale, we first draw a horizontal line (a b) a couple of inches long (see Plate 36, Fig. 88); set one point of a pair of compasses at the left-hand end (a) of this line, and, using the distance from C to 60 for a radius, describe part of a circle (be); then using b as a centre, and with a radius equal to the length from C to any number of degrees desired, cut the segment 6 c, as seen at d; draw a line joining a and d, and we have an angle of the desired number of degrees.

A FINE MODERN RESIDENCE. (For floor plans see back part of tills book).

Fig. 100 shows a diagonal scale for obtaining hundredths of an inch, which is found on some 2-foot squares, and on some draughting-scales. It is merely 1 square inch, divided vertically into 10 parts by horizontal lines. The upper and lower edges are divided into ten parts each: then a line is drawn from the upper left-hand corner to the first division on the bottom edge, another line from the first division at the upper edge to the second division on the lower edge, and so on. The space between the vertical line at the left, and the first diagonal line, is 1/100 of an inch on the first line down from the top; each space to the right on this line is 10/100 more; so that from the vertical line to the second diagonal line is 11/100 on this same line, to the third diagonal line is 21/100, and so on. From the vertical line to the first diagonal line is 2/100 of an inch on the second line down from the top, and every space to the right on this line is 10/100 more; so that from the vertical line to the second diagonal line is 12/100, and so on. From the vertical line to the first diagonal hue is 3/100 on the third line down from the top, 4/100 on the fourth line down, 5/100 on the fifth line down, and so on. To mark off any number of inches and hundredths, measure off the desired number of inches, less 1 and the decimal, then, with a pair of compasses, take 1 inch and the required number of hundredths, and add it to the length already measured off. For instance: If we want to measure off 35.58 inches, we first measure off 34 inches; then on the eighth line down from the top, from the vertical line to the first diagonal line, is 8/100, then to each of the others is 10/00 more; so we take five of these spaces, which, with the first space, makes 58/100; so we set a pair of compasses from the preceding inch to this point, and add it to the 34 inches already marked off, and it gives us the desired 35.58 inches.