Not sure if you have found the information you were looking for but here it is anyways.
Samuel and Mary Jane (GILLESPIE) Gaston left Ireland, via Londonderry, Jun 29, 1883 onboard the ship Sarmatian and arrived in Quebec City on Jul 9, 1883. The Sarmatian was part of the Allan Steamship Lines. I also have located a picture of this ship if you are interested.
Traveling with Samuel and Mary Jane were their children; Isabella, Charles, Samuel, Ellen, Mary Jane and Anne Eliza. Also traveling with the family was Jane Gaston, matron, age 60 and Alexander Robinson and his wife Mary Alcorn Robinson.
The Gaston party are found on page 14 of the ships passenger list.
Missing from the group is their oldest son, William Hamilton Gaston. It is assumed that William arrived ahead of the family to secure a residence for the family prior to their arrival. Also missing is Samuel's brother William and his family.
I have been working on the Gaston family for approximately 10 years now and have quite a bit of information. If you require any further information let me know and I will check my files to see if I have what you are looking for. I have a copy of the marriage registration record for Samuel and Mary Jane from Ireland.
You may contact me directly if you prefer.
Hope to hear from you soon.