Responses of Selected Plant Species to Elevated Carbon Dioxide in the Field 1

A snowmobile is shown having a chain case housing unit mounted between the engine and the drive track. The housing unit carries a driven shaft engaged for common rotation with the drive track. A braking disk is mounted on the shaft. A manually adjustable brake pad is mounted on one side of the disk and a fluid piston operated brake pad is mounted on the other side. Manually operable pump means are mounted on the handlebars to actuate the piston. Major portions of the braking unit are integrally formed with the chain case housing unit.