The ‘Calais-Douvres’ was a modified version of the ‘Castalia’, having two complete hulls and far more powerful engines. She arrived at Dover on 5 May 1878 and had her first trial run from Dover to Calais on 9 May. Her first working trip with passengers was on 29 May but on return to Dover she burst two cylinders in her engines and was driven against the Admiralty Pier, damaging her starboard bow. She was repaired locally and after trials in mid-July was put back into regular service on 29 July. The ‘Dover Express’ reported in February 1879: “The running between Dover and Calais of the ‘Calais Douvres’ during the past season appears to have justified expectation. She performed the trip with great regularity making good and quick passages. There was a great increase in comfort and considerable reduction in the incidence of seasickness.During the season, upwards of 55,000 passengers crossed in her, or an average of 715 per day, a number which on many occasions would have involved the necessity of running two of the ordinary mail boats.”Using some 40 tons of coal a day she was expensive to operate and found it difficult to maintain the demanding schedules of the mail ships. She was finally withdrawn in 1888.