These siege engines when only of moderate size were not always successful, as in some cases the walls of a town were so massively built that the projectiles of the enemy made little impression upon them. Froissart tells us that it was then the habit of the defenders of the walls to pull off their caps, or produce cloths, and derisively dust the masonry when it was struck by stones.

Some of the historians, mechanicians and artist from whom information on ballistas, catapults and trebuchets may be derived are as follows. I name them alphabetically irrespective of their periods :

ABBO : A monk of Saint-Germain des Pris, born about the middle of the ninth century, died in 923. He wrote a poem in Latin describing the siege of Paris by the Northmen in 885-886.

AMMIANUS MARCELLINUS : Military historian. Died shortly after 390. His work first printed at Rome 1474. The latest edition is that of V. Gardthausen, 1874-1875.

APPIAN : Historian. Lived at Rome during the reigns of Trajan, Hadrian and Antoninus Pius, 98-161. The best edition of his History is that of Schweighaeuser, 1785.

APOLLODORUS OF DAMASCUS : Built Trajan's Column, 105-113. Architect and engineer. Addressed a series of letters to the Emperor Trajan on siege engines (vide Thevenot).

ATHENEUS : Lived in the time of Archimedes, B.C. 287-212. The author of a treatise on warlike engines (vide Thevenot).

BITON : Flourished about 250 B.C. Wrote a treatise on siege engines for throwing stones (vide Thevenot).

BLONDEL, FRANCOIS : French engineer and architect ; born 1617 ; died 1686.

CEASAR, JULIUS (the Dictator) : Born B.C. 100 ; died B.C. 44 Author of the 'Commentaries' on the Gallic and Civil wars.

CAMDEN, WILLIAM : Born 1551 ; died 1623. Antiquary. Published his 'Britannia' 1586-1607.

COLONNA, EGIDIO : Died 1316. Archbishop of Bourges 1294, after having been tutor to Philip the Fair of France. His best known works are 'Questions Metaphysicales' and 'De Regimine Principum' ; the latter was written about 1280. Colonna gives a description of the siege engines of his time.

DANIEL, P?RE GABRIEL : Historian. Born 1649 ; died 1728.

DIODORUS (the Sicilian) : Historian. Lived under Julius and Augustus Cesar (Augustus died A.D. 14). The best modern edition is that edited by L. Dindorf, 1828.

FABRETTI, RAFFAEL : Antiquary. Born 1618 ; died 1700.

FROISSART, JEAN : French chronicler. Born about 1337 ; died 1410. His Chronicles printed about 1500. Translated into English by Lord Berners, and published 1523-1525.

GROSE, FRANCIS : Military historian and antiquary. Born about 1731 ; died 1791. Published 'Military Antiquities' 1786-1788.

HERON OF ALEXANDRIA : Mechanician. Lived B.C. 284-221. Benardino Baldi edited his work on arrows and siege engines, 1616 (vide Thevenot).

ISIDORUS, BISHOP OF SEVILLE : Historian. Died 636.

JOSEPHUS, FLAVIUS : Jewish historian. Born A.D. 37 ; died about the year 100. Wrote the 'History of the Jewish Wars' and also 'Jewish Antiquities.' Josephus, acting as commander of the besieged, bravely defended Jotapata A.D. 67, against the Roman general Vespasian. He was also present with the Roman army during the siege of Jerusalem by Titus, A.D. 70.

LEONARDO DA VINCI : Italian painter. Born 1445 : died 1520. In the immense volume of sketches and MSS. By this famous artist, which is preserved at Milan and entitled 'IL Codice Atlantico,' there are several drawings of siege engines.

LIPSIUS, JUSTUS : Historian. Born 1547 ; died 1606.

MEZERAY, FRANCOIS E. DE : French historian. Born 1610 ; died 1683. Published 'Histoire de France,' 1643-1651.

NAPOLEON III.: 'Etudes sur l'artillerie,' complied by order of the Emperor and containing many drawings of the full sized models of siege engines made by his orders, with interesting and scientific criticism of their power and effect.

PHILO OF BYZANTIUM : A writer on and inventor of warlike and other engines. Lived shortly after the time of Archimedes (Archimedes died 212 B.C.) : was a contemporary of Ctesibius, who lived in the reign of Ptolemy Physcon, B.C.. 170-117 (vide Thevenot).

PLUTARCH : Biographer and historian. Time and birth and death unknown. He was a young man in A.D. 66.

POLYBIUS : Military historian. Born about B.C. 204. His History commences B.C. 220 and concludes B.C. 146. The most interesting edition is the one translated into French by Vincent Thuiller with a commentary by de Folard, 1727-1730.

PROCOPIUS : Byzantine historian. Born about 500 ; died 565, the best edition is that of L. Dindorf, 1833-1838.

RAMELLI, AGOSTINO : Italian engineer. Born about 1531 : died 1590. Published a work on projectile and other engines, 1588.

TACITUS, CORNELIUS : Roman historian, Born about A.D. 61.

THEVENOT, MELCHISEDECH : 1620-1692 : Edited a book called 'The Mathematici Veteres,' containing several treatises on the siege operations of the ancients including the construction and management of their projectile engines. In this book are to be found the writings on the subject of military engines that were complied by Athenus, Apolloddorus, Biton, Heron and Philo. Thevenot was the King's librarian to Louis XIV. After his death the manuscript of 'Mathematici Veteres,' or the 'The Ancient Mathematicians' was revised and published by La Hire in 1693. The book was again edited by Boivin, an official in the King's library, who lived 1663-1726. The treatises contained in Thevenot were finally re-edited and published by C. Wescher, Paris, 1869.

VALTURIUS, ROBERTUS : Military author. Living at the end of the fifteenth century. His book ' De Re Militari' first printed at Verona, 1472.

VEGETIUS, FLAVIUS RENATUS : Roman military writer. Flourished in the time of the Emperor Valentinian II., 375-392. The best edition is that of Schwebel, 1767.

VIOLLET-LE-DUC : French military historian. Published his 'Dictionnaire raisonn. de l'Architecture,' 1861.

VITRUVIUS POLLIO : architect and military engineer and inspector of military engines under the Emperor Augustus. Born between B.C. 85 and 75. His tenth book treats of siege engines. Translated into French with commentary by Perrault, 1673. The most interesting editions of Vitruvius are those containing the commentary on siege engines by Philander. The best of these is dated 1649.