Edward Heyward in his book just mentioned gives still further details of contemporary ships. The rule which he mentions for ascertaining the length of the mainmast was that it should be half the length of the keel and once the length of the beam put together. The mainstay was to be in thickness half of the diameter of the mainmast. The shrouds were to be one half the thickness of the stay, and the topmast shrouds to be one half the main shrouds’ thickness. One ton of hemp required three barrels of tar. As to the ship’s boats of the _Sovereign_, her longboat measured 50 feet 10 inches long, 12½ feet broad, and 4¼ feet deep. Her pinnace was 36 feet long, 9½ feet broad, 3¼ feet deep. Her skiff was 27 feet long, 7 feet broad, and 3 feet deep. Fourth-rates only carried a longboat and a pinnace, fifth-rates carrying simply a longboat, while sixth-rates had only a 22-feet boat. The _Prince_ mentioned in the above list was the _Prince Royal_ of James I.’s reign. Her career had been a distinctly varied one. As originally launched she was the _Victory_ belonging to Elizabeth’s reign. She fought against the Armada, having been turned into a galleon two years before the fight. In 1610 as stated she had been rebuilt and called the _Prince Royal_, but this “rebuilding” was during this period something far more than any moderate adaptation. After the death of Charles I. her name was called during the Commonwealth the _Resolution_, and at the Restoration this was changed yet again to the _Royal Prince_. According to Le Sieur Dassie in his “L’Architecture Navale” printed in Paris in the year 1677, _Le Soleil Royal_ had a tonnage of 2500 as well as 120 guns and 1200 men. _Le Royal Louis_ had the same tonnage and the same number of guns, but only a thousand men. He gives also a very full and interesting inventory of _un vaisseau du premier rang_ of 2000 tons. Every detail is mentioned even to the _ornements de chapelle_. Very confusing is the naming of the three masts as used by the French at this time and embodied in Dassie’s work. Thus, as we hinted in a previous chapter, the foremast is the _misaine_, the main is the _grand mast_, while the mizzen is the _mast d’artimont_, or exactly the reverse of what we should have expected them to be named. From such a work as Dassie’s and, some years later, of Jean Bernoulli in his “Essay d’Une Nouvelle Théorie de la Manœuvre des Vaisseaux,” printed at Basle in 1724, we see how at last the scientific study of naval architecture had begun to make headway. The action of heavy bodies passing through the liquid sea, the relation of speed to design, were being slowly understood. Finally in 1794 the same scientific treatment was applied to sails. In “A Treatise Concerning the True Method of finding the proper area of the sails for Ships of the Line and from thence the length of masts and yards,” by F. H. af. Chapman, printed in London, the area of the sails in regard to the stability of ships is thoroughly entered into.