and judges throughout Scotland. Such officers eventually became hereditary with a sheriff-depute appointed to undertake the actual judicial work of the office. It is from these sheriffs that the modern day office of sheriffs principal derives, with a final settlement on the name by the Sheriff Courts (Scotland) Act 1971. The modern day office of sheriff derives from the sheriffs-substitute that were appointed by the sheriffs-depute (now sheriffs principal.) 16th century In 1540 an Act of the Parliament of Scotland mandated that sheriffs principal (along with bailies and stewards) should "hold all their three head courts by themselves in proper person, unless they have a just and lawful excuse". However, in the 16th century it appears that sheriffs-depute held office entirely at the will of the sheriffs principal, and undertook the vast majority of judicial work. 17th century In the 17th century, under the reign of Charles II, the number of heritable sheriffs principal increased in recognition of his restoration to the throne. By 1700, 21 of the 33 sheriffs principal were hereditary. 18th century In the 18th century, the office of hereditary sheriff principal was abolished by the Heritable Jurisdictions (Scotland) Act 1746, with the sheriffs-depute assuming the role and office of sheriff principal. 19th century Until about the middle of the 19th century there were 30 sheriffs principal. Of those sheriffs principal two (Glasgow and Edinburgh) were effectively full-time appointments while the remainder were part-time appointments filled by senior advocates, who are members of the Faculty of Advocates. Over the years there was a gradual amalgamation of sheriffdoms, with a consequential diminution in the number of sheriffs principal. 20th century In the 20th century the sheriff principal had appellate jurisdiction over summary causes in civil cases, with only cases that went to a full proof (hearing) having a right of appeal to both the sheriff principal and the Court of Session. In 1971, the Sheriff Courts (Scotland) Act 1971 confirmed the naming of sheriffs principal (affirming that the office of sheriff depute should be known as sheriff principal), and that sheriffs-substitute should be known as sheriff, stating: The number of sheriffdoms was reduced to six in 1975 by the Sheriffdoms Reorganisation Order 1974, with all the prior sheriffdoms abolished and replaced by the following sheriffdoms: Grampian, Highlands and Islands; Tayside, Central and Fife; Lothian and Borders; Glasgow and Strathkelvin; North Strathclyde; South Strathclyde, Dumfries and Galloway; with each