Lectures on scientific, historical, benevolent, or literary subjects, exhibitions of the fine arts, concerts, and amateur performances, the proceeds of which above the actual expenses are devoted exclusively to a religious, charitable or scientific purpose, or any firemen or policemen's pension fund within the city are exempt from the provisions of this subchapter. All shows, amusements and performances held at the fair grounds belonging to the Montgomery County Union Agricultural Society are exempt from the provisions of this subchapter during the time of its annual fair.
('85 Code, § 25.05(b))