Book excerpt: The authors review spectral induced polarization theory and describe some of the SIP method's applications through a discussion of their research in the People's Republic of China. In the first of four chapters, they discuss the electrochemical basis of SIP, offering proof of the validity of using the Cole-Cole model for describing complex resistivity spectra. In the next chapter, which addresses the SIP forward problem, they describe the scale-modeling laws for SIP, various forward algorithms, the behavior and variation laws of SIP anomalies, and effective SIP parameters. The third chapter discusses SIP inversion methods, including several methods of calculating the intrinsic spectral parameters of a polarizable body. In the final chapter, the authors describe their field tests applying the SIP method to prospecting for orebodies and oil and gas reservoirs. The material is introduced in part through a reprinting of a 1959 paper by Volume Editor James R. Wait titled 'The Variable Frequency Method."