The Act of Union 1707 and pre-Union Scottish legislation provided for 14 Members of Parliament (MPs) from Scotland to be elected from districts of burghs. All the parliamentary burghs (burghs represented in the pre-Union Parliament of Scotland) were assigned to a district, except for Edinburgh which had an MP to itself. The burghs in a district were not necessarily adjacent or even close together.
Until 1832 the Council of each burgh in a district elected a commissioner, who had one vote for the MP. The commissioner from the Returning Burgh (which function rotated amongst the burghs in successive elections) had an additional casting vote if the numbers were equal.
In 1832 the composition of the districts were amended, and the boundaries of a burgh for parliamentary purposes ceased to be necessarily those of the burgh for other purposes. The franchise was extended, and votes from all the burghs were added together.
There were further changes to the number and the composition of the districts in 1868, 1885 and 1918.
The district of burghs system was eventualy discontinued in 1950, but the term Burghs continued in use in the names of some constituencies until 1974.
The idea of parliamentary burghs continues to this day, in the form of burgh constituencies, which are distinct from county constituencies. This distinction is significant in terms of the expenses allowed to election candidates.

Summary of districts and burghs by period

Burgh constituency
List of burghs in Scotland