The middle layer should have the ribs running crosswise of the map so that the map mounting will be safeguarded from bending in either of the two different directions. Where very large wall maps are desired, six or more layers of straw-board may be used to give sufficient strength. If single sheets of straw-board cannot be found as large as the map itself, the map mounting can easily be built up of small sheets of straw-board, provided the joints in the straw-board are so placed that they will not be over each other to weaken the finished structure.

The straw-board backing for a map to be used with pins is not the best obtainable if the pins must be put in and taken out frequently. When, however, the pins are to be placed in the map and left there, the straw-board is just as satisfactory as any other backing for a

MAPS AND PINS

map. A layer of the cheapest kind of mushn placed over the face of the straw-board will prevent the pins from tearing the surface of the map if they happen not to be pushed in exactly straight. The use of cloth over the straw-board also permits of changing the pins many more times than would be feasible with straw-board without the cloth reinforcing.

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Reoiew 0/ Reiyttws

Fig. i88. Every Pin Dot on this Map Marks the Home of a Student of the University

of Cincinnati

By using a map printed in colors which do not photograph as black, the pins show up distinctly on the map