Farm Power: External Combustion Versus Internal Combustion

Farm magazine publishers had to be nimble when the competition between external combustion steam engines and internal combustion gas engines heated up.

external combustion versus internal combustion - Hart-Parr tractor ad
When internal combustion was first emerging as a threat to external combustion, this 1903 ad for the Hart-Parr gas tractor got The American Thresherman magazine in trouble with steam traction engine manufacturers.
Illustration: Farm Collector Magazine Staff