No, 1842 is before the start of civil registration so there isn't a marriage certificate.
There is a birth of a daughter Isabella to James Hardie and Margaret Findlay, on 22 May 1855 at 54 Rosehall Colliery, Old Monkland. Parents James Hardie, 39, ironstone miner, born Cumbernauld, and Margaret Hardie, maiden surname Findlay, 30, born Hurlate, Paisley, Renfrew. Isabella was Margaret's 8th child, and they had 3 boys and 1 girl living and 3 girls dead. (Bonus - I didn't have to shell out any credits because I had already coughed up to view another birth on the same page
)
1851 Census (transcription only) in Old Monkland: James Hardie, 32, born Cumbernauld, Dunbartonshire; wife Margaret, 25, born Paisley, Renfrewshire; James, 7; Charles, 3; Margaret, 5 months; all born Old Monkland.
1861 Census in Old Monkland: James Hardie, 45, born Cambuslang
*, Dunbartonshire; wife Margaret, 35, born Pollokshaws, Renfrewshire; James, 17; Charles, 12; Margaret, 10, William, 8; Isabella, 6; Robert, 4; Mary, 11 months, all born Old Monkland.
*Classic case of why you always need to look at the original. Cambuslang is not in Dunbartonshire, but Cumbernauld is. So this looks like a dud transcription.1871 Census in Shotts: James Hardy 53, born C
ambernauld, Dunbartonshire; wife Margaret, 45, born
Nilshall (sic transcription but compare with birthplace in 1891), Renfrewshire; Charles, 23; William, 18; Isabella, 16; Robert, 13; Mary, 10; John, 4.
1881 Census in Shotts: James Hardie, 66, born Cumbernauld, Dunbartonshire; wife Margaret, 55 born Barrhead, Renfrewshire; Robert, 23; John, 14.
1891 Census in Shotts: Margaret Hardie, widow, 65, born Nitshill, Renfrewshire; son John, 23.
Can't find her in 1901, but her age is absolutely consistent throughout with a birth in 1825/1826 in Renfrewshire. So she was certainly older than 76 when she died. That still makes her pretty young when she married, but well over 3 years old.
