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 between the different shades would be considerably clearer than it is in Fig. 179. A cut of this size and complexity is rather expensive when the Ben Day shading is used. Anyone wishing a cut made with Ben Day work would do well to get a rough cost-estimate from his engraver before actually giving the order.

Bertillon's "Course elementaire de Statistique Administrative"

Fig. 180. Height of the Houses in the Different Districts of Paris

The scale for this illustration should have been indicated on the chart so that actual numbers of houses could be read. The vertical dimension of the group of bars for each district shows the relative total number of houses. The horizontal dimension shows the relative number of houses of each height by stories

It will be noticed in Fig. 179 that the numerical scale-steps for different degrees of shading are uniform except at the smaller end of the scale. It would probably not be wise to show as white area all of the land valued at from $10 to $25 an acre, since such land makes up about half of the whole United States. A uniform scale varying by $25 per acre would give an erroneous impression regarding those important areas which contain land valued at less than $25 per acre but in which there is a large amount of farming.

Map diagrams of the type shown in Fig. 180 are sometimes useful. There is danger, however, of making a chart of this kind so popular in character that it loses in accuracy. The utility of Fig. 180 is at once