flues, 23 square feet, and grate surface, 160 square inches. The cyHnders 

 are 3 inches in diameter, 4 1-2 inch stroke; driving wheels, 14 inches in 

 diameter, i inch truck wheels, 8 inches diameter; wheels on the tender 

 and car, the same as truck wheels. The tender is mounted upon 6 and 

 the car upon 8 wheels. The car will seat 16 grown persons comfortably, 

 but has, at times, carried 32. Width of track, 18 inches; weight of en- 

 gine, 1300 pounds; weight of tender, with fuel and water, 450 pounds, 

 car 400 lbs. — in all, 2 1 50 pounds. 



In the model engine, the adhesion wheels are 6 inches in diameter, and 

 the gearing is arranged, so that when the engines which drive them, 

 make the same number of revolutions per minute, as the engines which 

 operate the side driving wheels do upon the level road, the engine and 

 train shall advance at a speed of one third of that on the level. In this 

 manner the same volume of steam is used upon the gradient, as upon the 

 level, and the power is increased in proportion to the diminished speed 

 of the train. The rapid exhaust of the auxiliary cylinders, maintains 

 the intensity of the blast whilst ascending the grade, and consequently 

 enables the boiler to generate an adequate supply of steam, so that a 

 deficiency of steam cannot occur on the gradients, which, would be the 

 case, if the blast were diminished by the smaller number of revolutions 

 per minute, and consequently less rapid exhaust. 



In constructing the model engine, some improvements were introduced, 

 which will be beneficial to the ordinary locomotive. The arrangement 

 of the eccentric and valve gear is such as to permit the upward and 

 downward motion of the axle, on which they are placed, without dis- 

 turbing the position of the valves, which is found to be so detrimental 

 to the working power of the best constructed locomotives, when rimning 

 over rough places in the road. This arrangement is not shown in the 

 drawing, but is so simple, that it may be rendered intelligible by a 

 description. The eccentrics are surrounded by bands, which are made 

 to slide up and down with the motion of the eccentric, (or with the play 

 of the axle,) in yokes, which are made to vibrate or slide in such manner, 

 that the sides of the yokes are always parallel with the sides of the pillow- 

 blocks, in which the axle boxes slide, so that the valve motion taken from 

 these yokes is never disturbed, in whatever part of the yoke the eccentric 

 band may be placed. [This valve motion is shown in fig. 29.] 



The working of all the parts of the model far exceeded my expecta- 

 tions. I refer particularly to the workmanship displayed in its con- 

 struction, and will mention one fact to the credit of those employed in 

 building it. The cylinders are of brass, with pistons with metallic 

 packing, and so well fitted, that, on turning the cranks of the upper 

 pair of cylinders, in a direction opposite to the set of the valve gear, 



59 



