5385. Stiff, C. L. March 5. [Addition to 8590/08.] Filter-bed tiles.-Tiles with one or more projections along an upper edge for maintaining the proper alinement between the rows and providing additional drainage or aeration space, as described in the parent Specification, are made with curved or ridged tops which may be either solid or perforated and with or without cross-ribs. Fig. 5 shows a tile with a projection extending continuously along one side and having feet of unequal length. Fig. 8 shows tiles having projections on opposite sides alternating with tiles having no projections.
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