166 APPENDIX. 



C. A portion of a sphere, forged on the shaft and turned to truth. 



D. The end of the shaft projecting into the wheel. 



E E. Part of the wheel centre, or nave, made in two parts, o and n, truly faced, bolted to 

 each other, and turned to fit the sphere on the shaft : the part n is again constructed in 

 two parts, for the convenience of removal when needful, and joined together by bolts 

 through two flanches across the nave. The radii of the wheel are clipped between o and 

 n, in recesses purposely cast for them. 



F F. Two crank-pins with spherical ends. 



G G. A double driving arm fixed on D. 



H H. Two crank-pins, also with spherical ends, and respectively connected by drag-links, 

 with the pins in the nave, in the same manner as Boulton and Watt have usually con- 

 nected their marine engine cranks. 



This arrangement obviously acts as a universal joint, and admits a deviation in the line 

 of bearings much beyond the limits of any thing required in practice. 



It is due to J. B. Humphreys, C.E., who has applied it to an IRON VESSEL constructed by 

 him for the Rio Doce Navigation Company, to state that our attention is attracted to his 

 practice by our knowledge of his long experience in these matters, he being well known as 

 the founder of steam navigation in Prussia so early as the year 1814. ED. 



