Roman siege engines BC, and surrounded by Roman fortifications. As was standard siege technique at the time, "ballistae" were placed up in the towers with other soldiers armed with either bows or slings. The onager was a post-classical Roman siege engine, which derived its name from the kicking action of the machine, similar to that of an onager (wild ass). It is a type of catapult that uses torsional pressure, generally from twisted rope, to store energy for the shot. The onager consisted of a frame placed on the ground to whose front end a vertical frame of solid timber was rigidly fixed;
History of Marine Animal Populations in some cases, cannot know about these changes. Only the interdisciplinary combination of expertise can fully develop the scope of what is known, unknown and unknowable about the environmental history of the oceans. The findings of the HMAP research effort are disseminated in the following forms:<br> Research Datasets: the HMAP Data Pages (at Hull University) is an open access facility that currently holds approximately 750,000 records drawn from historical archives relating to the case studies listed above. History of Marine Animal Populations The History of Marine Animal Populations (HMAP) is an international, interdisciplinary research initiative. It comprises the historical component