ON THE STABILITY OF HOUSING SECTOR INTERACTION: EVIDENCE FROM 42 METROPOLITAN AREAS*

ABSTRACT. Residential vacancy chain models based on White's (1971) application of Markov chain theory are used to simulate flows of housing vacancies through a set of interdependent housing market sectors. Measures of housing sector interaction are derived from such models. Our purpose here is to address the issue of time stationarity raised by their use. U.S. census data are available to calibrate such models at two, and sometimes three, points in time. Data from 42 different SMSAs are used to generate 56 cross-temporal comparisons with interobservation periods ranging from three to eight years. Stability of interaction is addressed from two perspectives–the sectoral perspective and the areawide perspective. Results are mixed and depend upon which measure of interaction is used, which perspective is addressed, and the duration of the interobservation period. However, within limits, findings support continued use of vacancy chain models.     

Integrating Landsat and Land Systems for Cover Maps in Southern Inland Queensland

Digital analysis of Landsat data is applied to up-dating land cover maps for the Goondiwindi district of southern, inland Queensland. The imagery was paired with climax cover maps obtained from land systems reports with analysis conducted separately for each of three climax cover types (open forest, woodland and open woodland). Computer classification using this approach produced readily interpreted and reliable results. This work demonstrates that Landsat can be used in conjunction with existing, land systems derived maps to produce data that combine the advantages of two approaches to environmental survey, the former being based on current land cover/land use and the latter on the original environment and its land use potential.     

The Roman wreck of c. AD 200 at Plemmirio, near Siracusa (Sicily): Interim report

A Roman wreck, named Plemmirio B^[1]i, lies on the rocky talus below the southern cliffs of Capo Murro di Porco, near Costa Bianca del Plemmirio (Penisola della Maddalena), prov. Siracusa, Sicily. The cargo of amphoras and iron bars, relatively well-preserved, is situated between 22 m and 47 m depth. Following brief examinations in 1974–1982, a University of Bristol expedition spent four weeks surveying the site in July-August 1983^[2] This paper presents an interim summary of these campaigns; a comprehensive report will be published after completion of excavations at the site^[3]. The archaeological deposit at Plemmirio B is characterized by concentrations of fragmented amphoras. There is no direct evidence for the structure of the ship, much of which may have disintegrated during the initial wreck process, but study of the artefact distribution suggests a vessel of fairly large capacity. The amphora consignment (which may have numbered no more than 200) comprised cylindrical African containers, 80% of which were form Africana 2A and 20% Africana 1^[4] w. The Africana 2A amphoras had internal resinous linings, and so may have contained a fish product rather than olive oil. Other amphoras exposed on the site were at least one Mauretanian Dressel 30 (Keay type 1) and two possibly intrusive amphoras of unclassified types. Ferrous concretions contained voids (hollow casts) which may once have been about 39 wrought iron bars, of two distinctive shapes. These, and several other concretions of unidentified forms, may represent a consignment of iron originally weighing approximately one tonne. Other finds from the wreck are two cooking pots, a small bowl or cup, a sounding lead, three fragments of tegula rooftiles, and two small stone blocks. One of the cooking pots confirms a date for the wreck based on the amphora association of circa AD 180–250, most likely in the first decade of the 3rd century. The amphora assemblage belongs to an important phase of commerce from North Africa represented by at least 20 known wreck cargoes; however, few of these sites have been scientifically recorded or are as closely dated as Plemmirio B, and the diversity of container types and cargo consignments on this wreck is of particular interest.