The rating system of the Royal Navy and its predecessors was used by the Royal Navy between the beginning of the 17th century and the middle of the 19th century to categorise sailing warships, initially classing them according to their assigned complement of men, and later according to the number of their carriage-mounted guns. The rating system of the Royal Navy formally came to an end in the late 19th century by declaration of the Admiralty. The main cause behind this declaration focused on new types of gun, the introduction of steam propulsion and the use of iron and steel armour which made rating ships by the number of guns obsolete. Origins and description The first movement towards a rating system may be seen in the 15th century and the first half of the 16th century, when the largest carracks in the Navy (such as the Mary Rose, the Peter Pomegranate and the Henri Grâce à Dieu) were denoted "great ships". This was only on the basis of their roughly-estimated size and not on their weight, crew or number of guns. When these carracks were superseded by the new-style galleons later in the 16th century, the term "great ship" was used to formally delineate the Navy's largest ships from all the rest. The Stuart era The earliest categorisation of Royal Navy ships dates to the reign of King Henry VIII. Henry's Navy consisted of 58 ships, and in 1546 the Anthony Roll divided them into four groups: 'ships, galliasses, pinnaces, and row barges.'" The formal system of dividing up the Navy's combatant warships into a number or groups or "rates", however, only originated in the very early part of the Stuart era, with the first lists of such categorisation appearing around 1604. At this time the combatant ships of the "Navy Royal" were divided up according to the number of men required to man them at sea (i.e. the size of the crew) into four groups: Royal Ships (the largest ships in the previous "great ships" grouping) mounting 42–55 guns and carrying at least 400 men; Great Ships (the rest of the ships in the previous "great ships" grouping) mounting 38–40 guns; Middling ships mounting 30–32 guns; and Small ships mounting fewer than 30 guns A 1612 list referred to four groups: royal, middling, small and pinnaces; but defined them by tonnage instead of by guns, starting from 800 to