164 



APPENDIX. 



Note 1. In illustration of what is observed in the first paragraph on the motion of paddle 

 wheels (page 119), the author of this paper has been prevailed upon by some of his friends to 

 consent to the insertion of Fig. 4, Plate LXXIX., which was drawn merely as a curiosity, and 

 not with any intention of having it engraved. The largest of the concentric circles in the 

 centre of the figure represents that described by one of the points of a paddle wheel, before 

 the vessel has any velocity, and the curves extending farther and farther on both sides represent 

 the curtate cycloids described by the same point, when the vessel has acquired the respective 

 velocities represented by the dotted horizontal lines extending from the middle of one node of 

 the curve to that of the next, the last being the. simple cycloid described when the velocity of 

 the vessel is equal to the circumferential velocity of the point ; the first-mentioned circle is 

 then the rolling circle, and the dotted circles those corresponding to the respective curtate 

 cycloids, the largest circle, considered as a curtate cycloid, having, of course, no rolling circle. 



Note 2. We have omitted to mention the six figures in Plate LXXX., which are intended to 

 show the distance between the nodes of successive floats in the different kinds of wheel. 

 Fig. 1 refers to the deep trial of the ' Salamander' with the common wheel, Fig. 2 to Field's 

 cycloidal wheel, Fig. 3 to Buchanan's, Fig. 4 to Oldham's, and Fig. 5 to Morgan's wheel, (all 

 these corresponding to Fig. 4 in the Plates LXXIV. to LXXVIII. inclusive), and Fig. 6 to the 

 performance of the ' Vestal,' Fig. 2, Plate LXXIX. In these figures it will be observed that 

 the distances between the nodes of the feathering floats are always greater than with fixed floats, 

 particularly those of the cycloidal wheel ; and that the nodes are most distant with Morgan's 

 wheel, as actually made, is seen in Fig. 6, although the wheel is much smaller than the others. 





*#* We have been favoured with a sketch of what we consider to be a very desirable im- 

 provement in the mode of connecting Morgan's wheel with the engine. 



To appreciate the improvement it must be borne in mind that the wheel, as hitherto con- 

 structed, has three main bearings in which it revolves, viz., one on the engine frame, one on 

 the ship's side, and the third on the spring beam. Experience has proved the great difficulty 

 of maintaining three bearings in a right line ; and has also shown a great increase in friction, 

 and in wear and tear, where any one of the three bearings has got, as workmen express it, 

 " much out of truth." 



