Do you mean the time it took a train to travel from one place to another, or the maximum speed that a train could achieve? If (as I suspect), you want the former information, then a railway timetable is your best bet, as others have already pointed out. That will show you how long it would have taken someone to ride the train from one place to another, plus it will show you what times someone could actually have taken a train from point A to point B. Just because Jack's at the station ready to ride a train doesn't mean that a train is available.
Another possibility, though, is that the Ripper may have simply "hopped" a goods train, and ridden away in that fashion. I do know that it's been suggested before that he escaped from the Buck's Row murder scene by jumping down onto a train as it passed through the cutting near the scene of the crime. If that's the case, then stations, timetables, etc. mean little. He's going to have to jump on and off the train when it's either moving slowly or stopped, though, which imposes some constraints. A group for railway enthusiasts would probably be the best place to get that sort of information.