Leg press, deadlifts, RDLs, lunges, leg extensions, leg curls, hack squats, split squats. All those will hit your legs, plus there variations. Do some sprints, run hills, stairs, those will hit your legs. Im sure there are more lifts I can't think of this second as well.
While natural gas occurs in nature as a mixture of methane and other gases, propane is actually a byproduct of both petroleum refining and natural gas processing.
The difference between propane and natural gas in domestic use comes down to their energy efficiency, cost, compression, storage, and risk factors. There is very little difference, however, when it comes to how well they perform in appliances for heating, cooking, or drying.