The Almond Aqueduct, also known as the Lin's Mill Aqueduct, is a navigable aqueduct that carries the Union Canal over the River Almond in Scotland, west of Ratho, Edinburgh.

The aqueduct was built to a design by Hugh Baird, with advice from Thomas Telford, in tandem with the Slateford Aqueduct and Avon Aqueduct, with which it shares its design.^[1] Baird had originally proposed to have only a single span, with embankments carrying the canal the rest of the way, but eventually decided to use the same design as the other two aqueducts.^[2]

Telford was not convinced that the stone arches were necessary in conjunction with the iron trough, but Baird used both on all three major aqueducts.^[1] Construction was carried out by Messrs. Craven, Whitaker and Nowell between 1819 and 1821, their success in building a stone bridge over the River Ouse making their tender for the contract "by far the most eligible."^[3]

In 1970 it was designated as a scheduled monument^[4] and in 1971 it was given Category A status, being individually listed for each local authority (the river denotes the boundary between West Lothian and Edinburgh).^[5][6] In 2003 the Union Canal became a scheduled monument^[7] thus causing the aqueduct to be scheduled twice and leading to the original designation being removed in 2019.^[4]

The Barton Aqueduct of 1761, and subsequent canal aqueducts in the United Kingdom, used large quantities of masonry and puddling to obtain watertightness.^[3] After the success of The Iron Bridge in 1789, however, cast iron was used by Telford on aqueducts such as Chirk and Pontcysyllte.^[3] Aqueducts built in the early part of the 19th century use either puddle clay or an iron trough in no particular pattern.^[8] The Almond Aqueduct uses an iron trough to achieve watertightness, as well as containing the outward pressure of the water, allowing it to be of more slender construction than a purely stone aqueduct such as the Kelvin Aqueduct.^[9]

Measuring 420 feet (130 m) long, it carries the Union Canal 76 feet (23 m) above the River Almond, from Edinburgh into West Lothian.^[10] A sluice into the Almond allows regulation of the water level in the canal, and near to the aqueduct is a feeder from Cobbinshaw Reservoir.^[2] The aqueduct can be reached by car by way of a track and by walkers and cyclists on the Union Canal towpath.

• List of canal aqueducts in Great Britain