I have a little information for you.David Fergus maticulated at the University of Glasgow, and married his wife Janet Black on June 1, 1788, in Glasgow as well.I don't know the names of his parents, unfortunately.
David Fergus led the `Relief' Presbyterian Church at Auchterarder, Tayside, Scotland, from 1787 to 1805 and his daugher Janet Fergus was born in Auchterarder in 1789.
In 1805 the Reverend Fergus accepted a call from the Presbyterian Church in Campbelltown and stayed there until 1822.He was moderator of the Relief Synod, 1805.I don't
know the name of the church in Campbelltown, but I suspect there was only one associated with the Relief Synod.A book on the history of the Scottish Presbyterian Church might help you there.
Janet Fergus married Alexander Langlands (it's Langlands with an S) on July 1, 1816.
Alexander was the son of Alexander Langlands senior and Elizabeth Kerr of Dundee.AL junior was a civil engineer and surveyor who had charge of some large construction work in Scotland, particularly of canals.According to family lore, he was a Presbyterian minister as well, and was steward to the Duke of Argyle, and got the Duke involved in a fish-raising scheme that lost a lot of money.
Alexander then decided it would be best to leave Scotland quickly, and did so without bothering to tell his presbytary he was leaving. I can't vouch exactly for the above story, but this is what I've been told.
The emigrants who left in 1822 were:David Fergus and wife Janet Black Fergus;
Alexander Langlands and wife Janet Fergus Langlands along with their two young daughers, Janet and Sarah, (a third daugher, Margaret, was born along the trip);
John, William, Agnes, and Sarah Langlands, nieces and nephews of Alexander Langlands;
Mrs. Agnes Turner, who was AL's sister, plus her son John;
and Donald and Peter McMurchy, nephews of David Fergus.
The party left in the Spring of 1822 and landed at Boston.By slow stages they reached Pittsburg.From there they took a flatboat down the Ohio River to Cumminsville, which is now a suburb of Cincinatti.Alexander Langlands bought a farm just north of the present day Spring Grove avenue in Cincinatti, and west of the Spring Grove Cemetary.
Not all the party chose to stay in the U.S., John and William Langlands deciding to return to Scotland.
Alexander Langlands died of Climatic Fever (whatever that was) in the fall of 1823.
David Fergus held services in the Langlands barn and at various places in and around Cincinatti, also travelling to neighboring territory by horseback to preach.He died in 1829, and his wife in 1845.The Reverend, his wife, and Alexander Langlands were buried in the nearby Spring Grove Cemetary, Lot 19, Section 52.(I haven't been there myself so I can't vouch for the exact location).
The family donated land from the Langlands farm for a public school for the town of Cumminsville, as well as land for a Presbyterian Church.
Sarah Langlands, niece of Alexander, married William Long and moved to Casstown, Ohio.
Of the daughters of Alexander Langlands, Janet married John Thomson (misspelled with a P in official record) on March 21, 1837, Sarah Langlands married Joseph Lakeman about 1840 and died without issue.Margaret Langlands married Frederick Parker on Feb. 26, 1846.
Mrs. Thomson later donated more land from their farm `Willow-burn' for a new Presbyterian Church (not the same as the one mentioned above,) which is on Hamilton avenue near Chase Avenue.
The children of John Thomson and Janet Langlands were: Janet, Margaret, James, Alexander L., John F., William N., George L., and Joseph Clarke.
The children of Margaret Langlands Parker were David F., John K., William, Richard, Alexander Langlands, Sarah, and Mary F.
Most of the above information comes from a sheet written by Alexander Langlands Parker in 1928.
Hope this helps you some.