Check the listing for details. Stull-Ealing Linear Air Track. Condition: Used. Listed at 80.00 USD. The Stull-Ealing Linear Air Track is a vintage scientific instrument used for measuring the velocity of air in a fluid. This device, dating back to the early 20th century, is a collectible item for those interested in the history of scientific instruments. The Stull-Ealing Linear Air Track is a valuable piece of equipment for collectors or individuals looking to add a unique and rare item to their collection of vintage science equipment. Used, please see photos for condition.