23.67 G.Francia, A new collector of solar radiant energy – Theory and experimental verification, (United Nations Conference on New Sources of Energy - Solar, Energy, Wind Power and Geothermal Energy, 3 may 1961); (in allegato: disegni tecnici). Collector constructed for the purpose of qualitatively confirming the properties of a beehive collector made of a materiale transparent to the incoming energy, but black for the reradiated energy. It cosists of about 150 glass tubes 14-15 mm in diameter, 250mm long and 0.2-0.3 mm thick, arranged so as to form a cylinder with wall of reflecting aluminium., 200 mm in diameter and 250mm long.