interference with the second endless conveyer belt 13 and the materials thereon in the preferred embodiment adjustable supports 14 are provided fig1 so that the second endless conveyer belt 13 may be adjustably located beneath the first endless conveyer belt 11 the adjustable supports 14 may include a cam mechanism or the like for adjusting the vertical position of the second endless conveyer belt 13 relative to the first endless conveyer belt 11 of course in the alternative the vertical position of the first endless conveyer belt 11 may be adjusted while the second endless conveyer belt 13 is fixed or both conveyer belts 11 and 13 may be made vertically movable to adjust the distance therebetween to produce a desired intensity of the magnetic fields also the height of the paddles 25 may be adjusted to scrape a top layer of the pile of the materials in order to provide efficient uniform exposure of the material on the second endless conveyer 13 to the magnetic fields it is necessary that the selection of the magnets and the spacing therebetween permit the magnetic material to fall back to the second endless conveyer belt 13 before it is attracted to the next downstream magnet further in this example as shown in fig1 the final magnet 23 includes double magnets 23 a and 23 b the magnets 23 a and 23 b attract for the final.