The Dominion Atlantic was a subsidiary of the Canadian Pacific and ran in the province of Nova Scotia from Yarmouth to Wndsor Junction.
It connected to Saint Johns, New Brunswick by a marine connection (Rail barge, I beleve) and also with the Canadian National at Windsor Junction, as well as having trackage rights into Halifax.
Main yards were in Kentville and there was also a connection to Truro where it served a gypsum mine.
Most of the line is gone, however, a section running from Windsor Junction to New Minas (52 miles) and the section to Truro (about 5 miles) are still in use as the Windsor and Hantsport Railway.
Gypsum is still the primary traffic.
Hope this helps.
Cheers.
Terry