ON PADDLE WHEELS. 159 



considerable amount of power must be spent in raising water. In the vessel alluded to there 

 was also no vibration whatever, so that a gentleman sitting in the cabin was quite surprised 

 to hear that she was not stopping, but going at full speed. Thus the defects, so much com- 

 plained of in the common wheel, are here quite obviated ; nor is it necessary for this, as it is 

 with Buchanan's wheel, to give the wheels an unusually great excess of velocity over that of 

 the vessel : indeed, the inclination of the floats may be regulated to suit any required ratio of 

 velocities. It is to be remembered that the proportions of the parts in the figure referred to 

 above are not such as would be chosen by the manufacturer : there would be fewer floats, but 

 they would have a greater depth, as may be seen in the elevation of ' Medea's' wheel, PI. 

 LXXXII., and in the diagram of the Trinity yacht ' Vestal's ' wheel, Fig. 1, PI. LXXIX. 



Fig. 2 represents a performance of that vessel, from data furnished by the engineer on board. 

 The wheels made 2.3 revolutions per minute, and the speed was 12' 16 statute miles an hour; 

 one revolution, therefore, carried the vessel forward 46 ft. 6^ in., and the diameter of the 

 rolling circle was 14 ft. 9-J in., or nearly eight-ninths of that of the wheel between the spindles. 



It will be observed that the floats are not vertical, as Mr. Barlow repeatedly calls them, 

 notwithstanding that he himself has made a drawing of one (see Fig. 2, PI. xxiv.), which we 

 presume to be that of His Sardinian Majesty's steam vessel ' Gulnare," from its resemblance 

 to a lithograph we have seen of that wheel, and in which the floats are evidently not vertical. 

 But Mr. Barlow not only calls them vertically acting floats, but calculates the proportion of 

 effective power as if they were really so, and, even on that supposition, his calculation would not 

 be correct, as the Editor has shown in a- note at the end of the paper. In Buchanan's wheel the 

 floats are essentially vertical, which we have shown to be rather detrimental to their action than 

 otherwise, particularly at deep immersions, when the loss of power is excessive ; and this dis- 

 tinction constitutes the principal advantage which Morgan's wheel possesses over Buchanan's. 



But, although the floats are not perfectly vertical, they approach nearer to that position 

 than those of Oldham's wheel ; therefore a rather greater proportion of the pressure is effective, 

 and a smaller proportion re-acts upon the arms of the wheel, the former being proportional to 

 the cosine of the angle included between the float and the vertical, and the latter to the cosine 

 of the angle between the float and the radius ; therefore the propelling effect bears -a greater 

 proportion to the power applied than the velocity of the vessel to the circumferential velocity 

 of the spindles, which is about the proportion of effective power with Oldham's wheel. Thus 



1 The following particulars relating to this vessel, which we have from an authentic source, may not be uninteresting to 

 the reader. She left Blackwall in the month of April, 1835, and steamed to Sheerness in 3 hours 15 minutes, or at a speed 

 of about 13-5 miles an hour, then proceeded, against a rather strong head wind, to Falmouth, where she arrived after a 

 voyage of 36 hours 30 minutes, making sometimes 10J knots, and generally from 9j to 10 knots an hour, the speed of the 

 engines being maintained between 25 and 27 revolutions per minute. She made the voyage from Falmouth to Lisbon in 75 

 hours 40 minutes, the sea being so rough that she had almost constantly one of her wheels immersed to the shaft, and the 

 other scarcely touching the water. In the following year she towed a 60 gun frigate, without any assistance, at the rate of 

 6 knots an hour, her engines making 18 revolutions per minute. Her usual speed was from 10 to 10-5 knots, and the 

 number of revolutions between 28 and 29. In February, 1838, after nearly three years of hard service, we learn that they 

 were repairing the wheels at Genoa, with some improvements, which had been introduced in the construction since the 

 ' Gulnare ' left this country. 



The diameter of the wheels between the spindles is 15 ft., and if we take 9~75 knots as the mean speed between Sheerness 

 and Falmouth, and 26 as the number of revolutions, we find the diameter of the rolling circle to have been 12 ft. 2 in., or a 

 little more than fmtr-fifths of the diameter of the wheel, which must be rather below than above the ratio of the effective to 

 the total power, exclusive of friction. 



