The ignition systems used in early farm engines were of two types, according to the author.
Early farm engines used either a rotary low tension magneto or battery and single winding coil as their ignition system.
There appear to have been at least two different types of ignition systems that have been used for make and break ignition on farm gasoline engines in years gone by.
1. Those used with the rotary low tension magneto (John Deere) where the points are in contact (or resting together) all of the time except a brief interval when opening to make a spark. I believe the set up on the Webster Tri-Polar works about the same. Contact is continuous while engine is coasting with hit and miss governing.
2. Those for battery and single winding coil, where the points are brought into contact only for a brief interval (15 degrees or so of a flywheel revolution) before separating to make a spark. These points remain open while the engine is coasting with hit and miss governing. Battery life should be long with this type and no overheating of coil should result. If battery and coil were substituted for magneto with point arrangement mentioned in No. 1, battery life would be very short and coil would no doubt overheat.
Rotary magneto is in reality an alternating current generator.