From Microfilm # C-11,472 at the National Archives in Ottawa from the RG10 Series Vol. 103, #288, a legal document. This is a land transaction between Lyman Burnham and Catherine Burnham and Henry Dochstader and I will quote the first paragraph --
"This Indenture made at the Grand River in the County of Haldimand in the District of Niagara in the Province of Upper Canada on the second day of May in the year of our Lord one thousand eight hundred and fifteen. Between Lyman Burnham of the Grand River aforesaid yeoman and Catharine Burnham his wife of the first part and Henry Dochstader of said Grand River yeoman of the second part"
So Lyman Burnham and Catherine Dochstader Burnham were married before May, 1815. And Chauncey Burnham died between November 1812, when he served in the Lincoln militia under Capt. Charles Askins, and May 1815 when Catherine is described as the wife of Lyman Burnham.