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Summary1. Ravens ( Corvus corax , L.) feed on rich but ephemeral carcasses of large animals. Nonbreeding juveniles forage socially and aggregate in communal winter roosts, which may function as 'information centres' regarding food locations. 2. In a large roost in North Wales, regurgitated pellets on the forest floor contained a variety of prey remains, which were more similar for ravens that had roosted close together the same night. 3. Sheep carcasses placed at varying distances from the roost were baited with colourcoded plastic beads. These were ingested and regurgitated in pellets back at the roost in aggregations, the spatial distribution of which consistently reflected the geographical location of bait sites. 4 Aggregations of beads at the roost grew daily with an increasing radius centred upon the first pellet per carcass. This mirrored the linear increase of six birds per day in the size of groups flying between roost and carcass each morning. Rates of recruitment were greater for carcasses closer to the roost. 5 Groups were led by a single bird roosting centrally within the aggregation. When individually identifiable (37·5% of cases), these individuals were dominant at the carcass and were among the minority of birds involved in acrobatic display flights at preroost gatherings. 6 When contrasted with data on two alternative groups of ravens peripheral to the main roost which foraged and roosted collectively, these results provide strong circumstantial evidence for raven roosts as structured information centres. The adaptive basis for competitive recruitment resulting in excessively large group sizes is also discussed.

Elemental analyses have been conducted on 61 coloured opaque glasses from the Malkata and Lisht New Kingdom glass factories. The presence of tin in several of the blue glasses suggests that a bronze casting byproduct or corrosion product was the source of the copper colorant for these glasses. A positive correlation between the lead and antimony concentrations of the yellow and green opaque glasses, plus a consistent excess of lead oxide in these glasses, suggests the use of antimony-rich cupellation litharge as the source for the Pb 2 Sb 2 O 7 colorant in these glasses. The metallurgical byproducts used to colour the Malkata and Lisht glasses provide an explicit mechanism for Peltenburg's theory of interaction between second millennium bc glassmakers and contemporary metalworkers.

Conversion efficiencies in excess of 50% have been measured in frequency-doubling experiments in KTP using divergent fundamental 1.064-,um beams. Various doubling schemes have been investigated to avoid reconversion effects observed in 9-mm-long crystals. The phase-matching angular acceptance bandwidth, damage-threshold observations, and a measurement of effective susceptibility relative to KD*P are also reported.

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