about the mean with wide throttle, as shown by indicator diagrams), and water as 941 to 1, there would be required to be evaporated 84-9 cubic feet of water to furnish that amount. Sea water weighing 64.3 pounds per cubic foot, the weight of water would be 5459-07 pounds evaporated per hour by 1027 pounds of coal, to which must be added the loss by blowing off, so as to maintain the saturation of the water in the boilers at of the ordinary hydrometer, equal to 11.93 per cent. of the total caloric imparted to the water; this would give an additional evaporation of 0.72 pounds, making a total evaporation of 6-03 pounds of sea water per hour per pound of anthracite coal: a rate of economical evaporation fully up to the ordinary standard of marine boilers. With the above consumption of coal, there were burned per hour 12-83 pounds of coal per square foot of grate. Each square foot of heating surface evaporated per hour 3.58 pounds of sea water. Speed. The mean speed of the Bibb at sea in ordinary weather was 7 knots per hour under steam alone, the wheels making 19 revolutions per minute; steam boiler pressure 15 pounds per square inch, cutting off at half stroke. Paddles dipping 42 inches. The circumference of the centre of reaction of the paddles was 46.34 feet. Taking the knot at 60823 feet, the slip of the centre of reaction of the paddles would be as follows: 46 34 × 19 × 60=5282760 ft.-speed centre of reaction of paddles per hr. 60823× 7=42578 67 ft.-speed of vessel per hour. or 19.4 per cent. 10248.93 ft.=slip of centre of reaction of paddles per hr. The loss of power by the oblique action of the paddles, calculated as the squares of the sines of their angles of incidence on the water, is 18.S per cent. The power actually developed by the engine when working with a total initial cylinder pressure of 28 pounds of steam per square inch, cutting off at half stroke, and making 38 strokes per minute; taking the back pressure on the piston at 4 pounds per square inch, would be as follows, viz: Including the effect of the expansion of the steam in the cylinder passages and clearance, the mean effective pressure will be 19-94 pounds per square inch of piston, and 2002.96 (area of cyl. in sq. in.) x 1744 (speed of piston in ft. pr. m.) x 19.94 33000, =210 8 horses power. Allowing 13 pounds per square inch of steam piston for the power required to work the engine, overcome the load on air pump, &c., we have, say 8.3 per cent. of the power thus absorbed. Taking the coefficient of friction from the experiments of Morin at 0.75 of the power applied, and taking the power applied upon the wheel to be the whole power developed by the engine, minus the power absorbed in working the engine, &c., the power absorbed by the friction of the load, will be, say 6.9 per cent. of the total power developed by the engine. Collecting the above, we have the following disposition of the in the Bibb: power Slip of the centre of reaction of the paddles, 19-4 per cent. or 40-90 horses power. All the revenue steamers originally constructed with the Hunter wheel, had, soon after trial, either the common side paddle wheel or screw propeller substituted. The experiment with the Hunter wheel, though totally valueless, except so far as proving experimentally the absurdity of that system of propulsion, which to any tyro in steam engineering needed no such proof, especially at such a cost as it was obtained, yet may prove valuable if it shall succeed in convincing others that although "all men are born equal in America," yet with a difference, and that gentlemen whose whole lives have been devoted to the study of the law, had better leave questions of engineering to professional engineers. For the Journal of the Franklin Institute. Notice of a new Steam Engine, Constructed by I. P. Morris & Co., Philadelphia, from Designs, and under the direction of Franklin Peale, Chief Coiner of the Mint of the United States. (With a plate.) The general design of this engine, (Plate xII.) conforms to the Gothic or pointed style, and its construction is what is commonly known as the steeple engine, working by simple high pressure; there are, however, peculiarities, and as far as is known to us, novelties in construction, which it is thought are entitled to attention. It will be observed on inspection of the engraving, that it is a combined or double engine, with the cranks at right angles; that it has no fly wheel, properly so called, but a pully or drum, from which the power is carried off by a broad belt (two feet in width). The drum is cast hollow, with chambers in the periphery, into which lead has been run, to counterpoise exactly, the pistons, triangles, pitmen, &c., so that the engine is in perfect equilibrium in every position, and performs its revolutions in an equal and regular manner. It will be observed, also, that it is perfectly symmetrical in all views, and that there are no steam or exhaust pipes visible on the exterior. A heavy bed plate, serving as a base, of twelve inches elevation, supports the frame and cylinders; it rests upon a brick foundation laid in cement, and secured by strong bolts built in. The steam passages have been cast in the bed plate, to convey the steam to and from the chests and cylinders, which stand vertically upon it. The pipes which convey the steam from the boilers to the engine, are placed in a passage or chamber, built in the foundation, in which chamber the throttle valve, controlled by the governor, is placed. The cylinders are placed eccentrically, within cylindrical cases, forming jackets, the intervening space, being the steam chest, containing the valve seats, and long slide valves, moved by the eccentrics, which are placed upon the shaft, immediately above; the eccentric position of the outer cylinder or jacket, allowing the required space on one side for the valve, and a sufficient space all round, for the channels and steam. The cylinders are fitted over one another, with conical metallic joints, and the cylinder covers contain the stuffing boxes of the piston and valve rods. It is this position and arrangement of double eccentric cylinders, giving space for the valves, channels, and steam, and forming a jacket round the working cylinders, which is claimed as an economic novelty, simple in its form, easy of construction, and presenting on the exterior a plain bright surface, an important security from loss of heat by radiation, or . condensation of steam in the interior; and finally, entirely divested of the usual disfiguring appendages of steam channels, pipes, joints, &c. The piston rods and guides are made of steel, the cross-heads travel upon the latter, with metallic packing of an approved alloy, with tightening screws. The pistons are furnished with what is termed steam packing, in other words, metallic plates, held against the surface of the cylinders by the pressure of the steam. The triangles or stirrups, connected in the centre of the bow, with the piston rods, are forged in one piece, and are planed up, and finished bright throughout. A simple solid pitman forms the connexion with the cranks, a double stub-end and strap connecting with the cross-head above, and a single one below, working on the wrist pin. The shaft and drum are supported on two cast iron frames, which conform in general features to a pointed arch window, strengthened by pannels, and enriched by columns, supporting the pedestals, and carried up to a finial; its exterior being decorated with appropriate crockets. The two frames are connected above the drum, by stays and braces, which are consistent with the style, so arranged as to afford space, within which the governor stands, centrally and appropriately, to regulate the motion of all that is below and around it. The engine is moved by steam at a pressure of eighty pounds, and is intended to be run at fifty revolutions per minute; this rate of motion is maintained without the slightest vibration, jar, or noise, and is calculated to give a sufficient effective force for all the heavy operations of the Mint. The power is applied, through the agency of belts, to the rolls, and other machinery, silently but efficiently, an evidence that in mechanics, as in moral science, the best effects may be produced with the least noise. For the Journal of the Franklin Institute. A Series of Lectures on the Telegraph, delivered before the Franklin Institute. Session, 1850-51. By DR. L. TURNBULL. Continued from page 194. Wheatstone and Cooke's Needle Telegraph. In 1834, Professor Wheatstone published a beautiful series of experiments on the velocity of electricity, which I noticed in the first of these lectures on the Telegraph. This seems to have had an influence in directing his attention to the subject of the Electric Telegraph. During the month of June, 1836, in a course of lectures delivered at King's College, |