Since the beginning of last week, however, four trains per day have been run regularly, stopping at the stations, and keeping their time as if working for traffic. The tube and valve appear in good order, and the whole has worked well, but the running in this manner can alone show the deficiencies which may still exist in the details necessary for stopping, and starting quickly from the stations, and all the other minor operations incidental to working the traffic in the ordinary course; and, until all these arrangements are completed, and the engines in more perfect order, I think it would be much better to defer at least the substitution of the Atmospheric for the locomotive working. Trains, in addition to those now running may perhaps be advantageously worked for the public, after a further short continuance of the present practising. The two engines completing the number to Newton are nearly ready for trial, and it is to be presumed that, after the experience of the past, the makers will be enabled to put them at once into an efficient state. The delays and difficulties attending the bringing into operation the Atmospheric System upon this portion of the railway have been beyond all anticipation, and beyond what any previous experience would have justified anybody in anticipating. The difficulties have all been seriously aggravated by the necessity (consequent, certainly, upon the original delays) of working the line with locomotives during the construction and completion of the Atmospheric apparatus. Not only has the constant occupation of the line interfered with the progress of the work, but it has been necessary to devise all the arrangements so as to admit stations, sidings, and line being worked either by locomotive or by Atmospheric in succession, or even at the same time. These difficulties, added to those always consequent upon the introduction of any new system, have been most wearying and incessant, and I am not surprised that the public and the proprietors should have been impatient. I trust the ultimate result will remove any grounds for disappointment. The stress of personal anxiety and personal fatigue, experienced by Mr. Brunel and by all who were engaged in the work, was very severe, and continued so to the end. Not only was the progress in the completion of the work slow, but in spite of every exertion the results were incessantly marred by unfortunate contingencies which involved further delay, discouragement, and expenditure. Moreover, the reaction which followed the railway mania had set in; calls were ill responded to, and great difficulty was experienced in raising the money requisite for the completion of the line.