The dc resistivity and thermoelectric power of bilayered perovskite $La_{1.4}(Sr_{0.2}Ca_{1.4})Mn_2O_7$ were measured as a function of the temperature. In the ferromagnetic phase, ${ ho}(T)$ was accurately predicted by $a_0+a_2T^2+a_{4.5}T^{4.5}$ with and without an applied field. At high temperatures, a significant difference between the activation energy deduced from the electrical resistivity and thermoelectric power, a characteristic of small polarons, was observed. All of the experimental data can be feasibly explained on the basis of the small polaron.