A few family, geographic and other notes: The Uncle and Aunt addressed by Marion here are no doubt Joseph Glencross (1819-1898) and his wife Marion Wilson. The Tam at the end of the first paragraph is their oldest son Thomas. The new baby Marion mentioned belongs to her brother James Brown and his wife Agnes Kerr.
Who is Corse? Not sure, but he sounds like a former neighbor at Tower Cottages? (Glencross is sometimes written "Glencorse," which adds to the complication of discovering who this is.) The parish of Sorn is in Ayrshire, and Auchenlongford is a hillside farm about 3 miles from the village of Sorn (according to Iain Hutchison's email notes on this letter, from a decade ago!).
Jane Rae Hunter of Raefield, then Cumnock... there's a Thomas Rae of Raefield in the Wilson list of graves at Sanquhar Kirkyard (link in left column), and there are several other Raes and mentions of Raefield in that list. So the mention of the name and place might well have been familiar to the uncle who grew up in the area.
Dec 11th 1876
Dear Uncle & Aunt
We was very glad to see your kind letter for we was wearing much to hear how you was all getting on and I hope this will find you all in moderate health when it reaches you. I am glad to be able to say that we are in moderate health in the meantime Aunt is sometimes very bad with the pains in her legs and arms she was thinking you had all forgot her together before we got the last letter she just takes fits of wearing to hear from you and she bids me say that you are all to tell Tam that he is to write a letter himself and let her know how is getting on
Tam is working with masons when the weather is dry but there is very little work going on around here and every thing is very dear Uncle William and his family are all well and James and his family are all well and he has another addition last month another daughter and it is named after me they call it Marion he has five alive and one dead and it is just like no times since he was married.
Corse left the Tower at the last term and went to a place in the parish of Sorn the name of it is West Auchenlongford and we have got one letter from him and he was liking the place well enough for the time I had very little news to send you this time but Jane Rae of Raefield was married on the 8th of this month to a Cumnock man his name is Hunter all acquaintences is well here as far as I know and Aunt sends her kind regards to you all every one and you are not to be so long in writting remember me to uncle John and Marion and Bryden and execpt of my kind regards to you all every one from your affectionate neice Marion Brown