The horizontal bar need be made only wide enough to show the various kinds of shading necessary to give a good contrast. Engineering dimension lines above each block in the bar are of great advantage 50%

for convenient reading. The dimension

lines permit of group- y<^rVh--''- ^'^<>';"--^-i'>'v-^;v /-^i^'^VivSo:^'^

ing in such a manner /'*^^•••X^";^^^'^;:i•>^i^^f^•^

that several of the detail blocks could be included in various sets of dimension lines to show such items as total fixed charges, total operating expenses, etc.

In this type of chart the actual figures representing the value of the components should be given for the use of any reader who may wish to draw his own conclusions or to make new combinations of figures different from those shown in the chart. As a general thing it is always desirable to have full data given on any chart. Fig. 1 gives all the data without in any way detracting from the ease of reading the chart itself.

It would be desirable to have a large number of the illustrations in this book printed in color. Charts which are made in color can readily bring out points which are not easily portrayed when only black ink is used. The reader should keep in mind for his own work that he should use colors in making those charts where colors are economically possible. For the purpose of this book, color printing is prohibitive

Disposition of the Gross Revenue of the Bell Telephone System for the Year 191 1