Another name for a Gas Harp is a Hall Hoop. These Hoops make great hall fixtures as well as great fixtures for small spaces. Hall hoops were used over Wash Stands with pitchers and bowls before modern plumbing was installed. A gas pipe would be on the ceiling in the corner or against the wall in a bedroom and Hoops would be for over the wash stand.
When people installed modern plumbing but were still lighting with gas there would be a hall hoop in the bathroom. This is a great light for small rooms as long as the ceiling is high. You usually need 24 inches of clearance to do a hall hoop. If you want the bottom to be about 6 foot nine from the floor then your ceiling needs to be 8 foot nine inches to do a Gas Harp.