Long pin with glass head used in conjunction with a piece of sheet celluloid cut into the shape of a flag.

William D. McAbee in the Survey

Fig. 197. Relative Soot Deposits in Indianapolis, March, 1912

The greatest soot tall is in the vicinity of railroad tracks Carefully selected samples of snow were melted and the soot of twenty-four hours weighed after the water was evaporarated. Spot maps of this kind can be quickly made by using short map pins pushed in till the pin heads touch the map

GRAPHIC METHODS

The Engineering Magazine

Fig. 198. Proposed Routes for a Comprehensive System of Passenger Subways for

the City of Chicago

On this map each dot is carefully located to represent 200 of the population. A spot map of this kind, made to some scale whereby one dot represents several people, is essential to any reliable study of transit facilities. After the spot map is made, the transit routes can be laid out to give the best service possible. Short map pins with heads touching the paper can be used for dots on the original map

MAPS AND PINS

Fig. 199. A Full-size Illustration Showing Some of the Different Arrangements of Map Pins and of Beads Which Can be Used for Map Work

The size of the various beads and pins can be determined by measuring on the above picture with an ordinary ruler, as the articles are shown in their exact size

4. A celluloid flag, with beads above the flag to represent quantity, or beads in different colors to denote various characteristics for the data portrayed. The grip of the sheet celluloid on the pin is sufficient to hold both the beads and the flag at the upper part of the pin.