The stairs were, indeed, very easy--the steps being very broad, and the "rise," as it is called, of each one being very small. Rollo and Jennie went on very gayly; and, as they kept about half a turn, of the staircase in advance, they were generally just out of sight of Mr. George and Mrs. Holiday, who followed somewhat more slowly behind. Jennie would have been afraid to have gone thus out of sight of her mother and uncle were it not that she could hear their voices all the time close at hand, and their footsteps, also, on the stairs. From time to time, as our party ascended, they met other parties coming down. When there were children in these descending parties, they tripped along very lightly in coming down; but Rollo and Jennie soon found themselves growing quite tired. So they stopped to rest. After stopping a moment, Rollo's mind seemed to swing, like a pendulum, to the opposite extreme. "Let us run, Jennie," said he, "and then we shall get up quicker." "No, it will tire us more to run," replied Jennie. "But then we shall get up all the quicker," said Rollo, "and so it will not make any difference. We may as well work hard and have it over quick as to work not so hard and have it last a great while." "Well," said Jennie, "then let us run." This reasoning of Rollo's was very specious and plausible, but it was very erroneous notwithstanding; for it is found by experience that the whole amount of fatigue which results from doing any given piece of work is by no means the same when it is done quickly as when it is done slowly. A horse, for example, if you allow him to jog along slowly, at the rate of three or four miles an hour, can travel forty miles a day, for months at a time, without growing thin; but if you drive him at the rate of eight miles an hour, he cannot stand more than ten miles a day for any long period. That is, he can do four times as much in amount, with the same degree of fatigue, if you allow him to do it slowly. It is curious that the case is precisely the same with a steam engine. A steamer can cross the Atlantic with a very much smaller supply of coal, if she goes slowly, than if she goes fast. One might imagine that it would take just twice as much coal to go ten miles an hour as would be required to go five; but in reality it takes more than four times as much--the higher rate of speed requiring a very disproportionate expenditure of power. If, therefore, you have a long way to walk, or a high ascent to climb, and are afraid that your strength may not hold out;-- Or if you have a horse to drive a long journey, and are afraid that he will tire out before he gets to the end of it;-- Or if you have a steamer to propel, and are not sure that you have coal enough to last to the end of the voyage;-- In these, and in all similar cases, the more slowly you go, the farther the force you have will carry you before it becomes exhausted.