Abstract: A solar heating unit which is covered at the top by a glass plate and at the bottom by an insulating layer, and at a height therebetween by an absorber plate which divides the unit into an upper and lower chamber through which forced air is guided to flow in opposite directions in contact first with the top and then the bottom surface of the absorber plate. The absorber plate has a smaller spacing from the glass cover than from the bottom insulating layer so that the air flows through the upper chamber at a faster rate than through the lower chamber. Due to this design the temperature gradient of the air on the two sides of the cover plate is held relatively low and heat losses through this cover are reduced at a minimum of expense. Several portable heating units of this design may be serially connected to form a free-standing solar heating assembly, for example, for supplying drying air to a grain bin.

Abstract: This invention employs a multiplicity of polygon-shaped members having magnetic edges which permit the members to be easily joined in order to fabricate two- and three-dimensional objects such as polygons and polyhedra for recreational and/or educational use.