142 APPENDIX. 



A few trials were subsequently made with Her Majesty's steam vessel 'Tartarus,' which may 

 throw some light on the relative qualities of the wheel under consideration, and Morgan's 

 wheel. This vessel formerly had a pair of the latter wheels with two fifty horse engines ; she 

 has now a pair of wheels with the divided floats, which have been made to go into the old 

 paddle boxes, and two seventy horse engines. When she was tried with the former, she was 

 ready for sea, drawing 12ft. 2 in. mean, and having an immersed midship section of about 

 254 square ft. ; the steam pressure in the boiler was 2f IDS., and the vacuum 27 inches. Under 

 these circumstances a mean speed of 8'508 statute miles was obtained, the wheels making 

 22 revolutions per minute. When tried in February, 1838, with Field's wheels, the mean 

 draught was 9 ft. 11 in., making her immersed midship section about 176 square ft.; the 

 steam pressure was 5 ffis., and vacuum 28 inches. The mean speed was 11-11 statute miles, 

 with 32 revolutions per minute. 



She was tried again on the 1 1th of March, with her lower masts and shrouds, having provisions 

 and 130 tons of coal on board; she drew about 11 ft. 8 in., and the speed obtained was 8'44 

 miles, with 24 revolutions : the radius of the rolling circle was consequently 4ft. 11 in., the 

 extreme radius of the wheels being 8 ft. 5 in., so that the slipping through of the floats on both 

 these trials was quite extraordinary, and can only be accounted for by the loss of resistance 

 in the first half of the stroke, and the want of a sufficient surface of paddle board, which 

 cannot be given without far surpassing the dimensions required by Morgan's wheels. 



Plate LXXXIII. represents the performance on the February trial : it has been drawn on a 

 very large scale, in order to make it less confused than it would otherwise have been ; but 

 there have been too many lines inserted that were not absolutely necessary, so that it is still 

 not so distinct as we could have wished. C is the centre of the wheel, of which a part is 

 shown on the right of the plate, as well as a part D D D of the rolling circle, at the commence- 

 ment of a revolution ; A A' A" is the curve described by the extreme edge of the outer board, 

 and B B' B" that described by the inner edge of the inner board of one set, and C C' the 

 distance travelled by the vessel, during a revolution ; at the termination of which the rolling 

 circle has arrived at the position D' D' D'. The radius C D of the rolling circle is about 4 ft. 

 1(H in., so that the distance C C' is about 30ft. 6| in. Towards the middle of the plate part 

 of the wheel has been drawn, showing the floats which are immersed at the same time with 

 the nodes of their respective cycloids, in order to give a more perfect idea of the action. The 

 set 1, 1, which is that of which the whole cycloid is given, is near leaving the water; of the 

 next set 2, 2, which has just passed the middle of the stroke, the outer board is about 

 to enter the path which the first set has just traversed, and the inner board has just left 

 the path of the outer one ; and of the third and fourth sets the inner boards are following in 

 the very track of the outer ones. It is obvious that the resistance to the floats must be very 

 much diminished by the naturally disturbed state of the water in which they move. Plate 

 LXXXII. b represents the above-mentioned performance with Morgan's wheel ; it has been 

 drawn on the same scale as the former, for the purpose of comparing the two. It will there 

 be seen that no one of the floats ever enters the path of another, and that the water in which 

 they move cannot be so much troubled as in the former case. The radius of the rolling 

 circle is 5 ft. 5 in., and the distance travelled in one revolution of the wheels consequently 

 34 ft. The quantity of steam consumed was nearly in the ratio of 5 to 7? and the body to be 

 propelled through the water more considerable, the draught of water being greater, so that 



