ON REEFING PADDLES. 61 



however be so small in the greatest extent of reefing ever required, that it is not necessary 

 to introduce it into the calculation. As far as its effect extends, it is favourable to the 

 reefing, as thereby the obliquity of action is diminished, and consequently the loss of power. 



ON REEFING PADDLES. 



In the commencement of a long voyage, a steam vessel is necessarily very deep in the 

 water, from the quantity of coals required for the consumption of the engine. This would 

 have the effect of diminishing the speed in a small degree, were the engine capable of exerting 

 its full power ; but from the wheel being also necessarily more immersed, there results a great 

 loss of the power of the engine, not only from the increased oblique action, but from the 

 number of strokes being reduced ; and having at the same time to combat with a greater 

 resistance, a very considerable loss of speed is the consequence. 



In the experiments given in Table I, the speed of two of the vessels is given both when 

 light and laden, from which the great amount of this loss will be seen. The first is the 

 Messenger with common wheels of 730 tons burden, and 200 horse power. Her speed with 

 60 tons of coals on board is 9'75 miles, and with 130 tons 8'00 miles an hour. 



Her sectional area of resistance could not have been increased in a greater ratio than 6 to 7, 

 so that the speed, if the whole power of the engine was brought out in the two cases, 

 ought not to have been reduced in a greater ratio than the cube root of these numbers, or 

 from 9'75 to 9 '25 miles per hour; hence there is a loss of 1*25 miles an hour from the bad 

 action of the wheels, and from the engine not being able to make its full number of strokes. 



The second experiment alluded to is the Flamer of 494 tonnage, and 120 horse power, 

 fitted with Morgan's wheels. Her speed with 15 tons of coals was 10'9, and 112 tons, 9'57 

 miles per hour ; the section of resistance would not be increased more than as 4 to 5, 

 so that the speed should not have been reduced to less than 10-12 miles; the remaining 

 loss of 0'55 miles per hour is therefore due to the diminished power of the engine, which, 

 although much less than in the common wheel, is still very serious. 



A similar comparison can be made between the Phoenix and the Salamander, which are 

 vessels of the same tonnage and horse power, and have nearly the same speed under similar 

 circumstances. The speed of the Phoenix light was 11 -7, and the Salamander laden 8-15. 

 Allowing a difference of section in the ratio of 11 to 15, which is the extreme between 

 a light and laden vessel, the reduced speed ought to have been 10'55, and there is there- 

 fore a loss from the combined effect of the bad action of the wheel and reduction of the 

 strokes of the engine, of 2'4 miles per hour. 



This serious loss of speed in a laden vessel, although greatly reduced by the use of Morgan's 

 wheels, as seen from the second experiment, as I have no doubt it will be in nearly an equal 

 degree by the cycloidal wheel, would be more effectually saved by reefing the paddles, by 

 which the whole power of the engine might be brought out, and the loss from oblique 

 action very much reduced. 



A ready method of reefing appears at present to be attended with some practical difficulties, 

 from the alterations that are made being required while the vessel is at sea. The advantages 

 which would be derived from it, particularly where speed is of importance, are evidently so 

 great, that I hope still to see it accomplished ; but should it ultimately be found im- 



