According to the regular schedule four trains should have left the Boston station in succession during the hour and a half between 6.30 and eight o'clock P.M.: a Saugus branch train for Lynn at 6.30; a second Saugus branch train at seven; an accommodation train, which ran eighteen miles over the main line, at 7.15; and finally the express train through to Portland, also over the main line, at eight o'clock. The collision at Revere was between these last two trains, the express overtaking and running into the rear of the accommodation train; but it was indirectly caused by the delays and irregularity in movement of the two branch trains. It will be noticed that, according to the schedule, both of the branch trains should have preceded the accommodation train; in the prevailing confusion, however, the first of the two branch trains did not leave the station until about seven o'clock, thirty minutes behind its time, and it was followed forty minutes later, not by the second branch train, but by the accommodation train, which in its turn was twenty-five minutes late. Thirteen minutes afterwards the second Saugus branch train, which should have preceded, followed it, being nearly an hour out of time. Then at last came the Portland express, which got away practically on time, at a few minutes after eight o'clock. All of these four trains went out over the same track as far as the junction at Everett, but at that point the first and third of the four were to go off on the branch, while the second and fourth kept on over the main line. Between these last two trains the running schedule of the road allowed an ample time-interval of forty-five minutes, which, however, on this occasion was reduced, through the delay in starting, to some fifteen or twenty minutes. No causes of further delay, therefore, arising, the simple case was presented of a slow accommodation train being sent out to run eighteen miles in advance of a fast express train, with an interval of twenty minutes between them.