Since both sizes and colors may be varied, and almost any number of beads used on one pin, there are practically unlimited possibilities for the showing of complex data.

16. Beads on a pin which holds down on the map a sheet of colored celluloid cut to the exact shape of a small land area to which attention is directed.

17. A sheet-celluloid marker held by a map pin like that seen in No. 8.

18. Celluloid-covered tack, available in different colors.

19. Celluloid-covered tack with stripes of different colors.

20. Celluloid-covered tack with printed numbers from 1 to 99 inclusive.

21. Celluloid-covered tack having a rough surface so made that the surface may be written upon with pencil or pen, yet erased afterwards or rubbed off with a moist cloth. Lettering may be made permanent by means of a coat of varnish.

22. Large size celluloid-covered tack available in different colors.

23. Large size celluloid-covered tack with stripes of different colors.

MAPS AND PINS 249

24. Very large size celluloid-covered tack.

It will be seen from the foregoing list that the possibilities for ingenuity in map and pin presentations are almost unlimited. The celluloid-covered tacks having large flat heads, shown in Nos. 18 to 24 inclusive, are not as generally used as they might be for map work. Map pins and tacks of this sort placed upon the surface of a map can give a spot map with any desired diameter of spots, no matter what size of map is used or what the amount of photographic reduction may be. It is simply a question of selecting from the spherical heads, 8 or 10, and the flat heads 18, 22, and 24, to determine which size head is best suited to the size of the original map and to the size of dot desired in the finished illustration.