This document discusses the application of analytic functions to fluid flow, electrostatic fields, and heat flow problems. It explains that for incompressible fluid flow, the complex potential F(z) describes the flow, with its real part giving the velocity potential and imaginary part the stream function. It also describes how the electrostatic potential satisfies Laplace's equation and can be written as the real part of a complex potential. Finally, it explains that steady heat conduction problems are governed by Laplace's equation and the heat potential is the real part of a complex heat potential, with constant values representing isotherms and heat flow lines.