Scales and keys should be located in respect to each other so as not to interfere with the easy interpretation of the curves.

2. KEY OUTSIDE GRID. If the key is placed outside the grid, it may be either above or below, the choice depending upon which location permits easier reading in conjunction with the curves.

When placed above the grid, it is often feosible to incorporate the key in the main title. (See illustration at the left.)

3. ARRANGEMENT. Items in the key ore normally placed one above the other in column arrangement.

When the available space is not suitable for column arrangement, items may be placed one after the other in horizontal lines.

4. ORDER OF ITEMS. Items in the key should follow a definite order; either the order in which the curves should be read or some natural order suggested by the data.

5. CURVE SEGMENTS. It is better to illustrate the curves referred to by showing sample segments rather than by merely describing them (e.g., is better than the description "dotted curve").

The curve segments should normally precede the designations.

It is permissible to enlarge the curve segments slightly to identify the design more easily.

The curve segments should be of sufficient length to show at least one complete unit of the design.

6. USE OF COLOR. Where color is used for curves it is effective to letter the curve designations in the same colors.

The arrow and designation •'EdKc of Paper" have been added to the original in order to indicate that the outside line is not a frame. See 382.