1849.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



211 



tides and slight breezes, each experiment embraced excursions in 

 various directions on the river. Once or twice, the boat went 

 straight as an arrow, but eventually the s(iuare paddles got the 

 better of the triangular ones. These dipped into the water with 

 little noise, and tlirew it off bcliind from their points. 



Most of the experiments were made in smooth water, and, ex- 

 cept slight currents — aqueous and aerial — under the most favour- 

 able circumstances. Two persons occu])ied the boat, and the 

 greatest care was exercised in preserving the shaft in a horizontal 

 position. When results were doubtful, the experiments were re- 

 peated, and generally several times. 



The same paddles (fig. 4) were next attached to the arms in the 

 position represented at fig. 5, the upper side 

 being, as in all other instances, 13 inches from 

 the centre of the axis. Through repeated trials, 

 they overcame the test paddles, fig. 3, and in a 

 rather more marked manner than fig. 3, surpassed 

 fig. 4. Tliey entered the water silently, but ob- 

 servers on shore thought they raised more water 

 behind, but did not raise it as high as fig. 3. 

 Their points were nearly three inches low er in 

 the water than the lower edges of fig. 3. The 

 boat described a circle of 400 feet, and another 

 of 600 feet. '''s- *• 



The same blades were next tried as fig. 6. From the experi- 

 ment fig. 5, it was inferable that, if inverted, the effect of the 

 blade on the boat would be augmented, as a 

 larger portion would have a longer sweep 

 through the water. Such was the fact, and to 

 such a degree, that first two, and then four, 

 were removed from the arms, when the remain- 

 ing four were found equal to the eight of fig. 3. 

 The plates were next raised, till their lower 

 edges were on a level with those of No. 1. In 

 that position, two inches of their upper extremi- Fi?. 6. 



ties were above the surface of the river; but, notwithstanding, 

 they had a decided advantage even then, over tlie square ones. 



Lastlv, the same blades were turned into the position of fig 7, 

 (being fig. 4 reversed). The boat was turned on No. 1 under all 

 circumstances, describing circles from 80 to 150 feet in diameter. 

 Four of them equalled eight of No. 1. Thgy were thought to 

 throw off more water behind than their competitors, which, fi-om 

 the greater extent of their extremities, is probably true. 



The next form tried was fig. 3, placed in the position of fig. 8. 

 These turned the boat round against the test ones, in circles vary- 

 ing from 50 to 200 feet. We then tried six of them against the 

 other eight, when there was little observable difference in the 

 results. Four were found superior, but three were unequal to 

 them. These, of course, entered the water without jarring, and 

 threw it off at their points. Mr. B. thought they threw up more 

 than fig. 3. 



on the last point— some thinking they were quite as effective as 

 the opposing eight. 



Fig. 7. 



Fig. S. 



Fig. U. 



Fig. 10. 



Fig. 12 



Fig. 13. 



Pig. 14. 



Fig. 11. 



Fig. 13 was a semicircle. Mr. B. undertook to test these. 

 Thev turned the boat in circles varying (from light winds and 

 tides) from 30 to 150 feet. Four were thought sometimes equal, 

 and sometimes superior, to eight of fig. 3. It is demonstrable 

 that these blades are less effective, though in a very sma.ll degree, 

 than those marked fig. 7, and, when reversed, more powerful than 

 fig 4. 



Fig. 13,— formed as in the figure, but not tried, as it w.as evi- 

 dent their value would be nearly that of fig. 7, probably a shade 

 above them, but too minute to be detected, except in perfectly 

 still water. 



Fig. 14,— a right-angled triangle, 7 inches across the top, and 

 ending in a point nearly 14 inches below it. These were, as might 

 have been anticipated, more effective than those of fig. 3. "Every- 

 thing about them," obser\ed Mr. B., "shows their superiority." 

 They, of course, entered the water without jarring. 



The same were attached to the arms in the position of fig. 15, 

 and were unable to compete with fig. 3. The latter had a slight 

 advantage over them. 



Fig. 9 were formed by removing the upper corners below, as in 

 the figure. Tliese seemed to have the advantage of fig. 8, but as 

 light winds troubled us, we felt some hesitation in pronouncing 

 them better. Four were superior to eight of No. 1. It was sup- 

 posed that a slight accession of resistance to the lower ends, 

 sweeping through the water, might be derived from opposing cur- 

 rents meeting in the forks, but we had no means to ascertain it, 

 if it existed. 



Fig. 10 — cut out of plates eight inches square, with one-fourth, 

 (minus a superficial inch) removed, as shown in the figure. After 

 several excursions, these were thought to exhibit a veiy slight ad- 

 vantage over fig. 3; but from subsequent tests, they seemed to be 

 balanced. We, on another day, reversed them, as 



Fig. 11, which had a decided preponderance over their competi- 

 tors. — Six predominated slightly over the latter, and four were 

 thought nearly equal to them. There was a difference of opinion 



Fig. 15. Fig. 16. Fig. 17. 



They were next reversed, as fig. 16, when they proved as effective 

 as figs. 7 and 12. — four being equally so as the eight opposed to 

 them. 



They were finally changed to fig. 17, when the boat was turned 

 so rapidly, as to make it difficult, with a wide oai', to keep her in 

 one direction. Four were removed, and then she described a cir- 

 cle in less than 50 feet. Two more were taken away, leaving only 

 a couple to act against the eight on the other wheel, and to which 

 they proved equal. 



From these experiments, it appears that, with equal areas, and 

 equal dip, triangular blades may be rendered twice as effective as 

 ordinary rectangular ones. This is made manifest by figs. 7, 12, 

 and 16,— :/o"J' of the former equalling eight of the latter. And 

 this, too, while the propelling surface of the smaller number was 

 only half that of the greater; for the four were as long in making 

 a revolution, as were the eight. Hence, the speed of a boat may 

 be increased by diminishing the number of her paddles — a fact 

 still further elucidated by fig. 17. 



There can, I think, belittle doubt, that the greater the velocity 

 of a steamer's wheels, the fewer (within certain limits) should be 

 the blades; and that, at the rate at which some of our boats go, 

 the number might be reduced with advantage. Some have three, 

 others four, and in more than one vessel, without any load on 

 board, I have seen six submerged at each wheel. In these cases, 

 is it not evident that each blade, on entering, plunges, not as it 

 ought, into water undisturbed, but into that which preceding ones 

 have already broken up, and set in motion towards the stern? It 

 would seem that one in the act of plunging, another sweeping 

 under the shaft, and a third leaving the surface, are all that are 

 necessary to be kept up; and that a greater number, as regards the 

 speed of a boat, is positively injurious. Yet, under a vague idea 

 of attaining a higher speed, the number of paddles has frequently 

 been nearly doubled. 



Snow, as every person knows, causes the wheels of land locomo- 

 tives to slip upon, instead of rolling over the rails. They revolve 

 as usual, but their carriages make little progress; hence much of 



23* 



