Note 1: (Norfolk) From BritWeb: Norfolk.
From Encyclopeadia Britannica:
South Norfolk: district, county of Norfolk, eastern England, occupying an area directly south of the city of Norwich. South Norfolk is principally an agricultural district extending across low-lying open countryside. Soils are generally fertile, and the old market centres (including Wymondham, Diss, Harleston, and Loddon) have small populations. A wide variety of crops, including barley, wheat, sugar beets, oats, and vegetables, is grown. Dairy cattle, pigs, and poultry are also raised. Several parishes (towns) and villages have imposing churches ranging in date from the Norman to the Perpendicular Gothic periods (11th to late 15th century). The district's southern boundary, the River Waveney, is popular with anglers. Freshwater marshlands abounding in waterfowl are commonplace in the northeast. Wymondham is the district seat. Area 350 square miles (907 square km). Pop. (1991 prelim.) 101,400.
North Norfolk: district, county of Norfolk, eastern England, occupying an area of 373 square miles (966 square km), bordering the North Sea for about 55 miles (89 km) on the north and northeast. Inland North Norfolk contains fertile agricultural areas around the market centres of Fakenham in the northwest and North Walsham in the northeast. The north-central part of the district has a generally less fertile series of low-lying gravel ridges extending southwest from the coastal town of Cromer. The Broads, in the east, are a series of near sea-level lakes that reach more than 15 miles (24 km) inland. They are surrounded by reed marshes abounding in waterfowl, and boating is popular there.
The coast has intermittent sand and gravel beaches with spits and islands at the western extreme, an area subject to accretion. East of Sheringham the coast suffers from wave erosion. Situated directly inland on the west is an alluvial plain of salt marshes and woodlands. The north-central and western-coastal resorts of Cromer, Sheringham, and the yachting centres of Blakeney and Wells-next-the-Sea are generally dependent on the summer tourist trade. Walsingham Abbey, which is located inland from Wells-next-the-Sea, is a pilgrimage site for both Roman Catholics and Anglicans; miracles have been associated with the locale since before the Norman Conquest in 1066. After 1967 the small town of Bacton on the northeast coast became the terminal for much of Britain's North Sea natural gas. Barley, wheat, and sugar beets are raised in the agricultural areas of the district, and crab and lobster fishing is locally important at Cromer and Sheringham. North Walsham and Fakenham have canning and food-processing industries. Cromer is the district seat. Pop. (1991 prelim.) 90,400.
Note 2: (the common forms) This likely refers to the practice that no couple would partner more than two times in a given evening (two dances at a time, for four total) and would not devote too much of their time to each other.
Jane Austen herself seems to have, perhaps, broken this rule on one occasion--with a gentleman rumored to be Miss Austen's first love, Tom Lefroy.
January 9, 1796, in a letter to her sister, Cassandra Austen:
...I am almost afraid to tell you how my Irish friend [Lefroy] and I behaved. Imagine to yourself every thing most profligate and shocking in the way of dancing and sitting down together. I can expose myself, however, only once more, becaue he leaves the country soon after next Friday...
In one source consulted here it says with regard to this letter:
"Jane refers teasingly to a flirtation to Tom Lefroy, nephew of the Lefroys of the neighbouring Ashe Rectory. It is not now possible to judge the importance of this episode to Jane, although tradition in the Lefroy family has it that Tom behaved badly to her." [The Illustrated Letters of Jane Austen, Edited by Penelope Hughes-Hallett, Clarkson Potter Publishers, NY, 1990, pg. 19.]
Note 3: (business in America) The event being referred to seems to have occurred somewhere around Sept-Oct, 1808, according to the Chapman chronology of Mansfield Park. Chapman does not give a theory on what the event being discussed actually was.
Note 4: (half-crowns and half-guineas) A half-crown was worth two shillings and sixpence. A crown (cr.) was worth five shillings.
A guinea was worth one pound and one shilling, so that would make a half-guinea worth ten shillings and six pence.
There were 12 pence in a shilling, and 20 shillings in a pound.