play with the best effect; the largest amount of propelling surface being introduced when it is most wanted, and not before. Like the feathering of oars and paddles, the surface is virtually diminished when its presence is injurious, and enlarged when it is most desirable.

But some will perhaps say, True, the blade dips with its point, but its base is the first to emerge, and consequently encounters a resistance equal to that evaded on entering. Not at all. It would be really so, if that base were as far out from the shaft as the point or apex, not otherwise. The resistance to a blade on leaving the water is greatest at its extremity, and increases of course with the width at that extremity. The outer edges might probably be slightly curved with advantage, so as to make each paddle a portion of an ellipse, as shown by dotted lines at p' p'.

I may be mistaken, but I think such paddles will be found preferable to ordinary shaped ones of equal surface. Besides being generally more efficient, they will cause less jar or tremor on striking the water; the shaft virtually will be strengthened, by withdrawing the strain from its outer ends-its weakest parts-to where it is stronger, and the work will be brought nearer to the power. When a cylindrical wheel is submerged by a vessel lurching, the strain on the submerged end of the shaft is extreme; but this can never happen to conical wheels, because of the reduced surface of the outer ends of the paddles.

To determine the best form of paddles-to ascertain whether it is better to extend them abroad from the sides of a vessel, or give them a greater dip and keep them nearer home-and, lastly, to find the limits outwards and downwards which yield the highest results-are problems interesting in themselves, and whose solution is of increasing importance to the world at large.

It is remarkable that the parent instrument, the Indian paddle, is invariably long and pointed. Find it where we will-in the hands of

savages, semi-tutored, or the civilized-the end is spearshaped. To what is this uniform result due, if not to experience? How is it that human sagacity in all times, as well as climes, has wrought the same figure out? If not possessing superior advantages, some tribes would surely have adopted another. But no. Everywhere man, as if impelled by a common instinct, has selected it. From its perpendicular position and action, it gave its name to our wheels. They are revolving paddles. Speed has always. been a prime object in the propulsion of canoes. Is there any essential difference between them and steamers, to require a different form and proportions in propelling blades?

Long triangular paddles are figured on Etruscan vases; Isosceletic blades, blunted and truncated, may be seen on classic sculptures.

The figure is a South Sea paddle in my possession. It resembles several in Montfaucon. Charon is often represented with one akin to it.

By increasing the dip of paddles, the circles they describe are en

larged, but in conical wheels that enlargement is confined to one side, while the width of the wheel and length of the shaft would be proportionably diminished. Such wheels could never be wholly raised out of the water by a vessel rolling. In the heaviest seas, they would have more or less hold of it.

Taking A for the position and proportions of a common paddle, what would be its comparative value if placed as at B; and when changed in its form, as at C, D, E, and F; and when doubled and the edges curved as F at G?

Where speed is everything, especially in vessels varying from 200 to 300 feet in length, instead of enlarging the present mammoth wheels, cannot a pair, if not more, of moderate sized ones be used to advantage at each side, as well as rows of oars in boats, and paddles in canoes?

E.

A Simplified Form of the Mechanical Lamp. By M. CAREAU.

The lamp of French invention, in which the oil is raised to the wick by means of machinery, is well known in this country, under the names of the Mechanical Lamp," "the Carcel Lamp," "the Diacon Lamp ;" and to those who have used it, or seen it used, we need hardly say, that for brilliancy and steadiness of light, it has never yet been equalled. The greatest objection to it is its expensiveness, the plainest lamp costing (in this city) about $15.

M. Careau of Paris has already made several improvements, which have been favorably reported on to the Society for the Encouragement of National Industry-and from their Bulletin for October 1847, we copy the accompanying plate and description of his last simplifications, by which the price in Paris is reduced to 15 francs. ($3.)

We feel confident that if any of our ingenious Eastern friends were to take the trouble to get up patterns for a lamp of this kind, they would deserve the thanks of oil burners, and be enabled to furnish at a moderate price, a lamp, superior even to the excellent ones which we have now.

Description of the Figures. Plate III.

Fig. 4. Front elevation of the mechanism.

Fig. 5. Plan of the same. The same letter refers to the same part in both figures.

A. A plate forming one of the sides of the oil-box, to which is attached the pump B, of tin, composed of two parts, one placed on the other. Each of these parts is cast in one piece, and they are attached together by a screw at each corner.

C. The barrel whose teeth take into those of a pinion D, upon the shaft E.

G G. The eccentrics upon the shaft E; a part of the circumference is embraced by the forks H H, which form part of the levers I I, whose fulcrums are in the pillars J J.

K K. Piston rods-four in number, two to draw in the oil, and two to raise it; an annular space between the rods, and the openings through which they work, regulates the ascent of the liquid.

L L. Projections cast upon the pump, in which the valves are placed. M. Plate fixed upon the pump, and carrying the ascension tube N.

Report on the Explosion of the Steamboat Edward Bates on the Mississippi River, August 12th, 1848, made to the St. Louis Association of Steamboat Engineers.

The undersigned, members composing the Standing Committee of the St. Louis Association of Steamboat Engineers, respectfully report, that in the discharge of the duties assigned them by the provisions of the sixteenth article of the Constitution of said Association, they went on board of the steamboat Edward Bates, on the 15th instant, for the purpose of examining into the cause of the recent catastrophe on board of said boat, and unanimously report the following as the result of said examination:

The Edward Bates has three double flue boilers, thirty feet in length, and forty-two inches in diameter; flues, sixteen inches in diameter, all made of iron one-fourth of an inch in thickness, and have been in use only since the first of March last. The iron is of a good quality, and the workmanship unquestionable.

The diameter of the safety valve is found to be three and elevensixteenth inches; the weight of the valve and lever is one hundred and thirty-two pounds; the pea hanging on the lever weighs one hundred and nine pounds, and was found attached to the lever at the distance of thirteen spaces or leverages, from the safety valve; and that the extra lead weight and wrenches attached to the safety-valve line, at the time of the catastrophe, weighed forty-two pounds, and were sixteen spaces or leverages from the safety-valve.

From the above data, it is ascertained that the weight on the safety valve was equal to a pressure of two hundred and six pounds to the square inch, without calculating the friction of the pulleys over which the line attached to the safety-valve was passed.

The Committee have been politely furnished with the written statements of Capt. Johnson, Wm. S. Belt, Clerk, I. C. Sitton, Pilot, and George G. Ambrose, Assistant Engineer, and also with the written statements of James W. Booth and Wm. Myers, passengers, the latter