Up tha Lum

Taken at the Ulster American Folk Park

As a wean I often heard burning something on the fire referred to as sending it "up tha lum". The lum being the chimney.
References to the lum can be found in Scots / Ulster-Scots literature from 1700 onwards eg.
1879 W. G. Lyttle Readings 77:
    Puir buddy, she lukit startit like, an’ sut doon awa at the tither side o’ the lum.
1786 Burns Halloween viii.:
    Till fuff! he started up the lum. 
I also uncovered a few sayins regarding the lum on the Internet.
Someone with a cast might have been referred to as - 'One eye on the pot and the other up the lum.'
  'Lang may yer lum reek.' — was a common expression to wish someone prosperity and plenty. 


Note my mother whose takin up computerin sent me an email to tell me that the entire sayin is:
Lang may yer lum reek an yer spicket (spigot) dribble.


Lastly 'Cryin' up the lum.' - it has been suggested that this phrase was used to stress the importance of self reliance. However I'm not entirely convinced that this is correct. Any suggestions on the meaning of this sayin' would be most welcome.