Heat Black used an analogy of water flow to understand specific heat capacity. The utility of this model was misinterpreted as fact. As a result the fluid, or caloric theory of heat was given a boost. In the model, heat is analagous to the volume of water in the tank.
Temperature is like the level of water in the tank.
The specific heat is like the surface area of the water in the tank. When water is allowed to flow freely between the tanks it behaves like heat tansfer in several ways. The amount of water lost from one tank equals the amount gained by the other The tank with the smaller area has a greater change in level as a result of the transfer.