20. The following societies may be registered under this Act:Charitable societies, societies established for the promotion of science, literature, or the fine arts, for instruction, the diffusion of useful knowledge, the diffusion of political education, the foundation or maintenance of libraries or reading rooms for general use among the members or open to the public, or public museums and galleries of painting and other works or art, collections of natural history, mechanical and philosophical inventions, instru-ments, or designs.