Industrial archaeology is defined as the study of the rangible evidence of social, economic and technological development of the period since industrialisation, generally the last 250 years. Marilyn Palmer and Peter Neaverson argue that industrial archaeology must be firmly placed within the context of mainstream archaeology, and be set within a methodological framework. The authors argue that conventional archaeological techniques and concepts need to be modified because of the nature of physical evidence and the availability of documentary sources. The analysis of sites and structures needs to extend beyond the functional to the cultural; only then will the complex nature of industrialisation be revealed in a more meaningful way than that derived from documents alone.