The bead wires for New York and for Boston were accordingly pulled entirely out of the map and the map was photographed without these two bead wires. The two bead columns were drawn in by hand on the surface of a photograph measuring 8 inches across the base of the map. With a little care, using a fine-pointed pen, bead columns such as these can be drawn in so that the ordinary observer would jiever notice that

MAPS AND PINS . 253

they were put on after the photograph itself had been taken. The angle at which the tall bead columns should slant can be determined by observing other bead columns in the same vicinity. In the case of Fig. 201, the angle was obtained by observing the bead column for Philadelphia. The reduction in size from the photograph on which the hand drawing was done, to the half-tone (in this case, a final reduction of from 8 inches to i^i inches) was sufficient to eliminate most of the imperfections due to hand work.

The use of beads opens up a whole new field for map presentation of statistical data. The Board of Sanitary Control for the Cloak and Suit and the Dress and Waist Industries of New York city made up two bead maps showing the fire risks and the sanitary condition in all the twenty-five hundred factories which come under the supervision of that Board. One bead on the map represents the condition for each factory. On the fire map the height of the multi-story loft buildings in which the difi^erent factories may be found is indicated by using one bead for each floor. Thus, in some of the taller buildings, twenty stories are indicated. Different colors of beads according to the fire risk or the sanitary defect to be shown mark the stories very plainly, and the heights of the bead columns show the heights of the buildings so that the bead map itself represents in miniature the sky line so typical of Manhattan Island.