In the case of these last the great resultant fact speaks for itself. The whole community knows when it sees a block system, or a stronger car construction, or an improved train brake suddenly introduced that the sacrifice has not been in vain--that the lesson has been learned. It is by no means always so in the case of accidents on bridges. With these the cause of disaster is apt to be so scientific in its nature that it cannot even be described, except through the use of engineering terms which to the mass of readers are absolutely incomprehensible. The simplest of railroad bridges is an inexplicable mystery to at least ninety-nine persons out of each hundred. Even when the cause of disaster is understood, the precautions taken against its recurrence cannot be seen. From the nature of the case they must consist chiefly of a better material, or a more scientific construction, or an increased watchfulness on the part of officials and subordinates. This, however, is not apparent on the surface, and, when the next accident of the same nature occurs, the inference, as inevitable as it is usually unjust, is at once drawn that the one which preceded it had been productive of no results. The truth of this was strongly illustrated by the two bridge accidents which happened, the one at Ashtabula, Ohio, on the 29th of December, 1876, and the other at Tariffville, Connecticut, on the 15th of January, 1878. There has been no recent disaster which combined more elements of horror or excited more widespread public emotion than that at Ashtabula bridge. It was, indeed, so terrible in its character and so heart-rending in its details, that for the time being it fairly divided the attention of the country with that dispute over the presidential succession, then the subject uppermost in the minds of all. A blinding northeasterly snow-storm, accompanied by a heavy wind, prevailed throughout the day which preceded the accident, greatly impeding the movement of trains. The Pacific express over the Michigan Southern & Lake Shore road had left Erie, going west, considerably behind its time, and had been started only with great difficulty and with the assistance of four locomotives. It was due at Ashtabula at about 5.30 o'clock P.M., but was three hours late, and, the days being then at their shortest, when it arrived at the bridge which was the scene of the accident the darkness was so great that nothing could be seen through the driving snow by those on the leading locomotive even for a distance of 50 feet ahead. The train was made up of two heavy locomotives, four baggage, mail and express cars, one smoking car, two ordinary coaches, a drawing-room car and three sleepers, being in all two locomotives and eleven cars, in the order named, containing, as nearly as can be ascertained, 190 human beings, of whom 170 were passengers. Ashtabula bridge is situated only about 1,000 feet east of the station of the same name,