[Footnote 3: The most careless observer has doubtless noticed that the front part of a locomotive rests upon the centre of a track, having four small wheels; the back and middle part, he will also remember, is borne upon large spoke wheels,--which are connected with the machinery; upon the size of these last depend the power and speed of the engine. The larger the wheels, the less the power, and the higher the velocity which may be got; again, the wheel remaining of the same size, by enlarging the dimensions of the cylinders the power is increased; and the wheels and cylinders remaining the same, by enlarging the boiler we can make stronger steam and thus increase the power. There may be seen upon the road from Boston to Springfield engines with wheels nearly seven feet in diameter, used for drawing light express-trains; while upon the roads ascending the Alleghanies may be seen wheels of only three and a half feet diameter, which are employed in drawing trains up the steep grades. Increase of steepness of grades acts upon the locomotive in the same manner as increase of actual load; as upon a level the natural tendency of the engine is to stand still, while on an incline the tendency is to roll backwards down-hill.] * * * * * HER GRACE, THE DRUMMER'S DAUGHTER. [Concluded.] The girl whose suggestion had brought about this change in her father's household, introducing anxiety and tears and pain where these were almost strangers, was not exceeding joyous in view of what she had done. But she was resolved and calm. It was everything to her, that night when she lay down to rest, to know that the same roof that covered her was also spread above the prisoner, and all the joys of youth passed into forgetfulness as she thought and vowed to herself concerning the future. It seemed, perhaps, a state of things involving no consequences, this sympathy that Elizabeth had shared with the gardener Sandy, when the prisoner's eyes gazed on them from his window, or turned towards them while he walked in the garden; but Sandy said to himself, when she told him that they were to have Laval's place in the prison, "_It took her_!"--neither did it seem incredible to him when she assured him that the new house was like home. He honestly believed that with the child--child he considered her--all things were possible.