LOCOMOTIVE ENGINE. 435 



each other, having a semicircular notch at the end fitted exactly to the cross head F, 

 which is a turned iron pin, one inch and three-quarters in diameter. The cross head F 

 is attached to the arms E E, of the socket B B, by wrought iron straps, G G, fitted 

 on to both, and fixed by the keys and gibs H and /; the gibs being required to 

 prevent the ends of the straps being sprung open by driving the keys. A small pro- 

 jection upon the cross head is fitted into a notch in one of the arms, D, in order to 

 prevent its turning round. 



The ends of the cross head K K are inserted into two guide blocks, L L, 6 inches 

 long and if inch thick, with flanches on the inner side ; these are made of steel and 

 are grooved on the sides to save metal. Each of these guide blocks is placed be- 

 tween two steel bars, M N, 2| inches wide, fixed firmly to the frame of the engine, 

 and shewn at A' A', in Plates XC. and XCI. The guide blocks and bars are 

 ground together and fitted accurately, enabling the blocks to slide steadily and easily 

 between the bars ; the upper bar, M, is five-eighths of an inch thick, and the 

 lower one, N, one inch thick in the middle, and five-eighths of an inch at the ends ; 

 the two being connected firmly together by small pillars, c, (Plate XC.,) fixed 

 into them at each end. The lower bar, N, is required to be stronger than the upper 

 one, as it is only supported at the ends. The upper bar, M, is fixed to a piece of 

 angle iron, 0, (fig. 19,) by bolts P, with countersunk heads, ground down flush 

 with the bar ; small pieces of brass, Q, being interposed between the bar and the 

 angle iron at each of the bolts, affording the means of adjusting the bars accurately 

 level when the angle iron is fixed on to the engine framing R. The bars M N 

 are adjusted exactly parallel to each other, and to the axis of the cylinder, so as to 

 allow the blocks, L, to slide behind them without any strain when moved by the 

 piston rod and cross head ; and they serve the purpose of guiding the end of the- 

 piston rod, and causing it to move always exactly in the line of the axis of the 

 cylinder. 



CONNECTING RODS. The connecting rods B'B', (Plates XC. and XCI.,) are 

 fixed at one end to the cross heads, and at the other end to cranks on the axle, C' C', 

 of the large wheels, D' D', of the engine ; they are of wrought iron, two inches 

 diameter in the middle, and taper down to one inch and five-eighths towards the ends. 

 The manner of fixing them to the cross heads, is shewn in figs. 17, 18, and 19, S 

 being the end of the connecting rod, enlarged at TT to three inches wide, and made 

 square and flat at the end. The brass bearing, U, is fitted to the end, and has 

 another brass piece, V, upon it, made octagonal on the back ; the two brasses are two 

 inches wide, and have flanches upon them at the sides, as shewn by the dotted lines 

 in fig. 18, that of the end brass V being semicircular. 



The brasses are fitted accurately on to a spherical ball, W, that is turned upon.the- 



