Before quite taking leave of science I will venture to touch upon a subject which, if not exactly science, is nearly related to it. At any rate, it can only be solved, if at all, through the medium of science. I can fancy I hear some votary of science exclaim with some indignation, "What is this doughty question which is to puzzle science?" To this I can only answer that if science has or can solve it satisfactorily, I humbly beg its pardon for doubting its powers. Well, the subject I am raising is expressed by the word Traction. Traction, I mean, as connected with pace. What is the difference in power required to move a given load at ten miles an hour and at five miles an hour? I have somewhere seen it argued as if it was the same, and that therefore the horses must suffer greatly over the latter part of a stage, supposing that their powers were less and the weight to be drawn remained the same. Of course, the weight does in one sense continue the same, but every coachman who has had any experience in driving will have observed how much longer time it requires to pull up a coach going at a high speed than one at a slow pace; which of itself proves that after the coach is once set in motion and has acquired a fast pace, the exertion required to keep it going is considerably reduced. Without for a moment forgetting the cardinal truth that "it is the pace which kills," it is quite apparent that the disease and the remedy, to some extent at least, travel together. Another fact which can be attested by all old stage coachmen, and which goes strongly to prove how much reduced the draught is by pace, is that four light horses can get a load up a steep pitch at a gallop which they would be quite incapable of surmounting at a walk.
Then there is another item which adds to the complexity, which is this—that the greater the weight, the longer the time required for pulling up. It would seem, therefore, as if a heavy weight, to a certain extent, assisted its own propulsion. The same circumstances are observed on the railways, and, probably, from the hardness of the metal on which their wheels run, it is still more apparent than on a road. I was once travelling for a short distance upon a locomotive engine without a train behind it, and upon asking the driver how long it would take to bring his engine to a standstill, he said, "I could stop it almost immediately now, but it would be very different with a long train behind her." Probably there are few coachmen who have driven any great number, of miles through whose brain this question has never trotted, but without arriving at any solution of it. At any rate, I confess my own ignorance, and only throw down the question at the feet of science after the custom of the ages of chivalry, when the herald threw down the gauntlet into the midst of the assembled knights, to be picked up by the best man.
The following narrative will convey some idea of the force of velocity which appertains to the wheels of a coach travelling at a high speed:—
As the "Mazeppa" coach was proceeding on her journey from Monmouth to Gloucester, when descending a hill about three miles from the former place at a fast pace, the tire of the near hind wheel came off, and the impetus was so great that it caused it to pass the coach and run on for nearly half a mile, thus proving that the power required to draw a carriage when it has attained much speed must be very much diminished. It only requires to be kept moving.
CHAPTER IX.
A NOTE ON THE HORN.
Many guards on the day coaches carried key bugles, on which some of them were able to play exceedingly well, and helped to while away many a half hour on the journey; but on the mails and night coaches, the former especially, straight horns were employed. Formerly these were all made of tin, hence the "yard of tin," but in later years a good many copper or brass ones came into use, and a few, in quite late years, adopted a twisted horn without keys, much like the infantry field bugle used in the army.
J. Sturgess del. et lith.
M&N. Hanhart imp.
OBSTRUCTION ON THE BRIDGE.