I just joined genealogy.com and noticed you're looking for MacDermid information, and that your last name is Helmer. I have MacDermid and Helmer relatives from Glengarry and Stormont, including a great grandfather named Duncan MacDermid. The dates you gave don't match the dates I have, though. The Duncan MacDermid I'm related to was born on May 8, 1825, the son of Peter McDermid and Jane McGregor.
In some family history I'm compiling, I have a note that a lot of the MacDermid family history can be found in a booklet entitled McDermid Geoealogy, 1757-1897, compiled by McDermids of Glengarry County, Ontario. I'm not sure if I have that booklet, however. I'll have to let you know later.
By the way, my great-grandfather Andrew MacDermid (son of Duncan MacDermid and Jane Clendenning) married Cassie (Catherine) Helmer, and Cassie's brother Dave Helmer married Andrew MacDermid's sister Cassie (Catherine)-- in other words, a sister and a brother married a brother and a sister.
My grandfather, Charles Nelson MacDermid, born June 6, 1895 in Glengarry County (near Martintown) and his brother Kennie, spelled their last names differently. My grandfather used the "Mac" prefix and his brother Kennie used simply "Mc".
My mother did a lot of research into the Scottish roots of the MacDermids/McDermids/MacDiarmids of the Glengarry area,