The correct answer is option 'C' - centrifugal type.

Explanation:
A governor is a device used to control and regulate the speed of engines or machines. It consists of rotating masses driven by the engine and connected to a control mechanism. The Hartnell governor is a specific type of governor that operates on the principle of centrifugal force.

1. Hartnell Governor:
The Hartnell governor is a centrifugal governor named after its inventor, James Hartnell. It is widely used in steam engines to control the fuel supply and maintain a constant speed. The governor consists of two rotating masses connected by links to a control mechanism.

2. Centrifugal Force:
Centrifugal force is the outward force experienced by a body rotating in a circular path. In the case of the Hartnell governor, the centrifugal force acts on the rotating masses.

3. Working Principle:
When the speed of the engine increases, the centrifugal force acting on the rotating masses also increases. This force causes the masses to move outward, which in turn, moves the links connected to the control mechanism.

4. Control Mechanism:
The control mechanism of the Hartnell governor consists of a sleeve and a spindle. The movement of the links connected to the rotating masses causes the sleeve to move up or down the spindle.

5. Fuel Supply Regulation:
The movement of the sleeve controls the fuel supply to the engine. When the speed of the engine increases, the sleeve moves up, reducing the fuel supply. Conversely, when the speed decreases, the sleeve moves down, increasing the fuel supply.

6. Speed Regulation:
The Hartnell governor continuously adjusts the fuel supply to maintain a constant speed. If the speed of the engine increases beyond the desired value, the governor reduces the fuel supply, slowing down the engine. Similarly, if the speed decreases, the governor increases the fuel supply, speeding up the engine.

In conclusion, the Hartnell governor is a centrifugal type of governor that uses the principle of centrifugal force to control and regulate the speed of engines or machines. It is widely used in steam engines and other applications where speed control is essential.