Hi Fred
N.Br means North Britain. The document you have was signed by John Mackenzie, minister and Alex. Gunn the session clerk.
I have information on your Macleods. William was born on the 20th and baptised in Rogart on the 23rd. He is the son of Donald Macleod, a crofter and merchant, and Ann Murray of Muie, Rogart.
Donald was born 1766 and died at Muie on 4 June 1838. His wife was born around 1786 and died at Muie on 15 September 1859. They also had Mary, born 1807; Robert born 1808; John born 1814; Patrick born 1817; George, born 1819; Alexander born 1822 [died 25 august 1902 at Muie] [married Ann Munro in Rogart on 3 Feb 1863] and Janet, born 1825.
There are undoubtedly more children between 1809 and 1813. Registers for this period are not available.
Alexander Macleod and his wife Ann Munro had Ann, born 1865; Donald born 1867; Catherine born 1869 and Dolina born around 1875. In 1881 census Alex was farming 8 acres and a merchant at Muie. Their children Annie, Kate and Dolina were with them.
Hope this helps. Lots of info on Sutherland on my web site.
Christine Stokes