John, my understanding of the difference between an ocean liner and a cruise ship is an ocean liner is designed to sail between two ports in the shortest possible time, whereas a cruise ship does just that - it cruises, in a much more leisurely fashion. The classic ocean liners were used on the trans Atlantic run, and competition between rival companies to see who could cross in the shortest time was quite intense. The ship holding the fastest crossing time was awarded the Blue Riband. The first Queen Mary and Queen Elizabeth were such liners, and faced competition from ships such as SS France, and SS United States. I think the SS United States was the last ship to hold the Blue Riband, but I am open to correction on that. The QE2 is generally regarded as the last of the true ocean liners, but even she was built with cruising in mind, a fact that stood her in good stead when jet aircraft became the principal form of fast travel.
A curious piece of trivia concerns the number of funnels some of the early liners had. Apparently the widely held belief at the time was the more funnels a ship had, the safer and more powerful it was, so some vessels, for example Mauretania, had 4 funnels, one of which was a dummy. Even the SS United States while having only 1 funnel, this was made disproportionately large, to give the appearance of great power.
Peter.