Abstract. An alternative example of the method of multiple scales is presented. This example arises in the study of the classical heat equation with a slowly varying flux imposed at one end. The module presents introductory ideas about dimensionless variables, multiple-scale expansions, and scaling of the dependent variable. The necessarily obfuscating algebraic computation is less than that for more familiar multiple-scale examples, such as the perturbed oscillator. The results are analyzed for both their physical and mathematical importance.