first powerful cannon batteries, but, though they had many of the same architectural facets as true castles, they served a purely military function (rather than serving as residences). Deal Castle remains one of the most impressive such Device Forts, and was perfectly symmetrical, with a low, circular keep at its centre. Over 200 cannon and gun ports were set within the walls, and the fort formed a firing platform with a shape that allowed many lines of fire. In addition, its low curved bastions were designed to deflect cannonballs. Cannon were now an inexorable part of English warfare. Cannon also saw use in the Tudor navy (where a cannon was a "gun", and a cannonball a "shot"). The French "culverin" was adapted for naval use by the English in the late 16th century, and had a significant advantage over the ballista that had previously been used in naval warfare. This cannon was of relatively long barrel and light construction, and fired solid round shot projectiles at long ranges along a flat trajectory. One of the first ships to be able to fire a full cannon broadside was the English carrack the Mary Rose, built in Portsmouth from 1510–1512, and equipped with 78 guns (91 after an upgrade in the 1530s). It was one of the earliest purpose-built warships to serve in the English Navy (thought never to have served as a merchant ship), and her crew consisted of 200 sailors, 185 soldiers, and 30 gunners. With the Age of Discovery, rivalry developed between European colonies and the importance of cannon in naval warfare increased. Many merchant vessels were armed with cannon and the aggressive activities of English privateers, who engaged the galleons of the Spanish treasure fleets, helped provoke the first Anglo-Spanish War, though it was not one of the main factors. A fleet review on Elizabeth I's accession in 1559 showed the navy to consist of 39 ships and in 1588, Philip II of Spain launched the Spanish Armada against England. In a running battle lasting over a week, the Armada was scattered and defeated by the English navy. 17th century A description of the Gunner's art is given during the English Civil War period (mid-17th century) by John Roberts, covering the modes of calculation and the ordnance pieces themselves, in his work The Compleat Cannoniere, printed London 1652 by W. Wilson and sold by George Hurlock (Thames Street).