21076.03 66 4.09° 89-90 1.931488 1-919378 89 4-10 1005.80 94 4-08 1 3.28 969.89 66 66 1-006784 66 3-4 2.001740 1.986395 1-007725 66 66 5-6 2.000630 1.985469 1-007636 7-8 1.998515 1.981835 1-008416 TABLE III.-Compressibility of Carbonic Acid Gas. 5 3.28 969-72 66 66 12-13 1.995740 1.971465 1.012313 15-16 1.999835 1.974288 1-012940 2789.55 66 4247.28 66 22-23 1.999732 1.9624181-019014 24-25 2·000188 1.962043 1-019442 26-27 2.000630 1.962431 1.019465 66 66 66 72 2.67 970-31 17445-23 1.169215 "6 1.169437 66 1-167003 "6 1-166640 62-64 2.892713 2-474063 1-155787: 1.155865 1.154232 66 1-153681. 4 4.43 5 4.41 6 4.40 7 4.22 TABLE IV.-Compressibility of Hydrogen Gas. 2-4 4.820120 4.845916 1 14.40 969-19 4431·14 4.41 1-2 2-001134 2-003971 0·998584 0-994676 0-995020 8-10 3-4435853-467140 10 TABLE V.-Compressibility of Hydrogen Gas. 1 10-02 968.97 11165-36 10.00 2 10-00 1939-91 22.002025 2-0098500-996107 66 2-3 2.002314 2-010480 0-995938 24-26 2.259936 2.278090 66 0-992031 66 0.991980 0-992290 66 0-992209 0-992207 0-992217 5555.32 TO THE COMMITTEE ON PUBLICATIONS OF THE JOURNAL OF THE FRANKLIN INSTITUTE. On Paddle-Wheels. The following thoughts on paddle-wheels are respectfully submitted: As I have not kept the run of recent propositions on the subject, it is possible that the view I have taken may be neither novel nor correct: if so, I can only claim the merit of having suggested what I thought might be both useful and new. But theory is one thing and practice another. The former is polite and complaisant; the latter, a sturdy, inflexible fellow, that no coaxing can soften., One will often accompany a votary in his wanderings, the other won't deviate a hair'sbreadth if an inventor's salvation depended upon it. That any plan involving movements of paddles on their arms, with the view of feathering them, and more especially their suspension on pinions for that purpose, will never receive the sanction of modern engineers, I feel fully persuaded. Such wheels are too complex to be trusted, particularly on the ocean, while their auxiliary movements are all but incompatible with the requisite velocity of the chief one. Notwithstanding innumerable projects for improving or superseding it, the old paddle-wheel still holds its own, and like the oar, seems to deride all attempts to beat it. In modern steamers it scarcely differs an iota from those used in Roman galleys, mediæval ferry-boats. Paddles in use are rectangular blades, arranged parallel to the shafts to which they are attached, and around which they necessarily describe cylinders. They constitute cylindrical paddle-wheels. Their acknowledged defects are chiefly two. 1. When they strike the water their tendency is rather to depress it than to cast it behind them, which in fact they cannot do, till, in their progress downwards, they are passing or about to pass under their axes; hence a portion of the power that drives them is wasted on indirect action. 2. So also when rising to the surface, they lift the fluid, produce what is called backwater, and thereby uselessly expend another portion of the motive treasure. Viewed in connexion with a boat at rest, these are serious drawbacks. To a certain extent they are diminished with her speed; still they are drawbacks, and, unfortunately, are inseparable from fixed blades revolving in circles round their axes. The question then is: Can anything be done to make fixed paddles more efficient by lessening the water's resistance to them at those parts of their stroke or sweep, when their propelling property is weakest, and without adding to it when that property is greatest. I submit that, in some degree, this desideratum may be realized by conical paddle-wheels. These may be made either by altering the figure of common paddles, or their position on the arms, viz: by inclining them to their shafts. Of obvious modifications of such wheels, one will be sufficient for an illustration. Paddles shaped like p p, instead of uselessly striking the surface of the water with their entire length, dip first their pointed extremities, and when half their depth is immersed the larger part of their faces will be still without, contrary to rectangular ones, whose immersed areas increase pari passu with their dip. Here, the most powerful part of the blade is withheld from the water till it can be brought into Vol. XVI.-3RD SERIES.-No. 4.-OCTOBER, 1848. 23 |