Commercial operations at Stanley Mills ceased in 1989

The 18th Century mill was discovered beneath Stanley Mills, which at its height was a major centre for the cotton spinning industry.

Heritage agency Historic Scotland is now altering its regeneration plans to incorporate the corn mill's remains.

The project is part of a multi-million pound scheme to preserve the site.

Part of the cotton mill building, seven miles north of Perth, is also being converted into housing.

Corn mill

Archaeologists believe that the first Stanley cotton mill, built in 1786 using Richard Arkwright's revolutionary factory methods, used the system which had carried water to the old corn mill to power its own machinery.

It is thought that as the cotton operation expanded and thrived, the corn mill - which experts said may have eventually been destroyed by fire - fell into disuse.

Historic Scotland major projects manager Jane Rahil said documentary evidence indicated that the corn mill was built in 1736.

It is hoped the visitor centre will open in 2007

"This is an exciting discovery as it shows how the Tay's tremendous power was used for grinding corn before the cotton mills were built here," she said.

"In fact, the ruins are in very good condition, there are some lovely millstones and you can clearly see what the structure was once like.

"We are now looking at the best ways to preserve this important archaeological find."

In 1995 Stanley Mills was placed into the care of Historic Scotland and given a Grade A listing.