So how do we fix this system? Well, we fix the system by adding another object to the heat engine, something called a cold body. We saw that we had a hot body for the specific purpose of conduction. Well, now we have a cold body that also is specific for conduction. In other words, when this piston moves this way, there's an increase in temperature. And the increase in temperature causes energy to transfer via conduction from this place to this place.