In the essay Stim & Dross: Rethinking the Metropolis Lars Lerup attempts to indentify urbanism (in the case of this essay, the American city of Houston) in terms of Stim and Dross; these relate to points in time and space of high and low intensity. In the first page of his essay he defines Stim as stimulation, and Dross as waste products or worthless(ness). He then defines and locates Stim and Dross within the architectural language of urbanism; Stim can be loosely identified as the main city landscape and its operation, and Dross as the resultant suburban sprawl. He finds the blurring of the two particularly interesting: “I was interested in a kind of suburban architecture: plain box buildings, shopping centers, that kind of sprawl.” (86:1995)

Houston Skyline, Texas, USA
Lerup observes the town in layers, considering the city as canopies, downtown areas and airspace “This double reading brings canopy and downtown together conceptually since driving inside the Downtown may prompt an appreciation of its megashape […]” (86:1995). He describes the existence of Stim and Dross as a vital aspects of a metropolis city, and their dual existence as a stimulus for interesting architectural to occur and develop; “Only in the hybrid field of stimdross may we begin to rethink and then recover from this holey plane some of the many potential futures.” (99:1995)

Lerup’s Diagram of Zoohemic/Aerial Fields: Stim and Dross (1995)
I agree with Lerup’s ideology of the importance of Stim and Dross, that the balance of the two can be an important site for juxtapositions of interest and potential new urbanisms. However the essay is written with the case study of Houston only, and it would be a useful experiment to consider the application of this theory to other existing urban landscapes.
I feel that Lerup’s Theory is aligned with certain aspects of Allen’s ‘Mat-Urbanism’: the notion of viewing the urbanism in layers, and the ensuing flat landscapes of sprawling suburbia as a potential site for new kinds of urbanism to manifest themselves, with the city providing peaks of activity and the suburban landscape providing the space for people to actually live. Lerup, evolves the theory into a reality, suggesting that not all areas of the city are a hive of activity, that activity and programme are transient and that the urbanite and indeed the city itself experience and rely just as much on areas of seemingly less activity. Therefore, in order to have Stim, the metropolis must also have Dross, and vice versa.
http://www.frieze.com/issue/review/drosscape/ (Accessed on 3rd December 2010)
http://www.cascoprojects.org/data/html/c01413.html (Accessed on 3rd December 2010)
Lerup, Lars (1995) Stim & Dross: Rethinking the Metropolis. Assemblage (25) pp. 83 - 100