Hi Monica,
No, I haven't been able to find him (William Alexander Johnstone) any earlier than his marriage in 1872. His marriage certificate is where I found his father's name and occupation from, and he was listed as deceased at that time.
Now I've rechecked, ancestry threw up two possible death dates for him (WAJ), being either 1906 or 1920. But it's his father I'm trying to trace more than him. I know he came from Rutherglen, but apart from that, I can't find any trace of him or his father Samuel. I don't know if it's me, because I'm struggling with a maternal great grandfather who also came from Scotland. So I'm wondering whether I'm missing vital information because I'm not used to researching Scottish ancestry. My Welsh ancestry I've had much better luck!
Thanks for your help,
Lisa