English single-masted ships began to be replaced by two or three masted ships with high pointed bows to resist waves and sails enabling the ship to sail closer to the wind. 200 tuns was the usual carrying capacity. The increase in trade made piracy, even by merchants, profitable and frequent until merchant vessels began sailing in groups for their mutual protection. The astrolabe was used for navigation by the stars. Consuls were appointed to assist English traders abroad. Henry IV appointed the first admiral of the entire nation and resolved to create a national fleet of warships instead of using merchant ships. In 1417, the war navy had 27 ships. In 1421, Portsmouth was fortified as a naval base. For defense of the nation, especially the safeguard of the seas, Parliament allotted the King for life, 3s. for every tun of wine imported and an additional 3s. for every tun of sweet wine imported. The most common ailments were eye problems, aching teeth, festering ears, joint swelling and sudden paralysis of the bowels. Epidemics broke out occasionally in the towns in the summers. Leprosy disappeared. Hospitals were supported by a tax of the King levied on nearby counties. The walls, ditches, gutters, sewers, and bridges on waterways and the coast were kept in repair by laborers hired by commissions appointed by the Chancellor. Those who benefited from these waterways were taxed for the repairs in proportion to their use thereof. Alabaster was sculptured into tombs surmounted with a recumbent effigy of the deceased, and effigies of mourners on the sides. Few townsmen choose to face death alone and planned memorial masses to be sung to lift his soul beyond Purgatory. Chantries were built by wealthy men for this purpose. Gold was minted into coins: noble, half noble, and farthing. The commons gained much power in Parliament under Henry IV because he needed so much taxes that the commons had a hold over him. Also, as a usurper King, he did not carry the natural authority of a King. The lords who helped his usurpation felt they should share the natural power of the kingship. Also, the commons gained power compared to the nobility because many nobles had died in war. Shakespeare's histories deal with this era. The Commons now has a speaker.