Co Cavan to Dundee?

[Lisa in California]

My husband's ancestor is Patrick Joseph Tierney (previous thread about his marriage in Dundee, Scotland):
http://www.rootschat.com/links/091s/ 
He was born in 1838, immigrated to New York c1869 after his marriage to Margaret Flood; settled in San Francisco.

Might there be a reason why someone would have left County Cavan and lived in Dundee?  (The county and city seem so far apart from each other.)
 

[aghadowey]

First reason that comes to mind is he moved due to work- do you know is occupation(s) in Scotland and U.S. (might be some clues there).

[Lisa in California]

Thank you for your reply, aghadowey.

Apparently, he was a labourer while in Scotland and worked for the City of San Francisco c1900.  My husband's relatives (who have since passed on) said that he worked in Golden Gate Park, in San Francisco.  (I can look for his occupation on census returns.)

In 1880 he was working at a hydraulic mine in California.
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1870: Labourer
1880: Miner
1900: Labourer, Street
1910: City Park, Labourer