Verum inter haec inquies Persa vineis civitatem pluteisque circumdabat, et erigi aggeres coepti, turresque fabricabantur, frontibus ferratis excelsae, quarum fastigiis ballistae locatae sunt singulae, ut a propugnaculis propellerent defensores,
Translation :
But meanwhile the restless Persian was surrounding the city with sheds and mantlets, and mounds began to be raised and towers were constructed; these last were lofty, with ironclad fronts, and on the top of each a ballista was placed, for the purpose of driving the defenders from the ramparts;
Edition :
Ammianus Marcellinus. With An English Translation. John C. Rolfe, Ph.D., Litt.D. Cambridge. Cambridge, Mass., Harvard University Press; London, William Heinemann, Ltd. 1935-1940.