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mon method of rack and pinion, and presuming that it might perhaps be of use to soine of your readers, (in case the method is not already known,) I venture to forward to you a description of it. The modification consists in the use of crank and connecting rod, as shown at A A, fig. 1 and 2, instead of rack and pinion, as in the common airpump. Across the upper part of the piston rods b b, are guide pieces ee, which move, with the piston rods, up and down in grooves formed in the upright posts D DD, and keep the piston rods perpendicular.
It will be seen that by this method the pistons may be made to alternate without that jaring which accompanies the rapid turning backward and forward of the winch in the common method, while, at the same time, the winch C, may be turned constantly forward with greater ease than backward and forward. The barrels E E, the pipes F G, and the remaining parts constructed as in the common air-pump.
Chowan county, North Carolina, Sept. 9, 1844.
NOTE.It would be an improvement to place the two cranks at right angles,-as this would have a tendency to make the action of the pumps more regular.
Improvements in Sub-Marine Blasting at Spithead. Lieut. Barlow, the present executive engineer officer at Spithead, who conducts the operations with no less zeal, intelligence, and activity, than his able predecessors, has tried numerous experiments in
the firing of gunpowder by the voltaic battery, partly with the service charges used in breaking up the timbers of the wreck, in tin cans not usually exceeding from 44 lbs. to 55 lbs. of gunpowder, and partly with small experimental charges of a few ounces, by desire of Gen. Pasley, who wished to carry out Lieut. Hutchinson's ingenious plan of firing submarine charges by one conducting wire only, instead of two, (see Journal, vol. vi, p. 337,) using the water of the sea to complete the electric circuit. In these experiments Lieut. Barlow first found that it was unnecessary to let down a piece of wire with zinc plates attached to it from the voltaic battery into the water, as had been done by Lieut. Hutchinson, for the circuit was equally good when the wire alone was used; and on repeating those experiments in Gen. Pasley's presence, the correctness of this principle was sufficiently proved, but a difficulty occurred which had not been experienced before, viz., that it required two plate batteries of ten cells each, to fire a charge at a distance of 200 feet, with the single wire, whereas one of Prof. Daniell's batteries of eight cells only, which is inferior in power to a plate battery of ten cells, had always fired submarine charges instantaneously in former years by the double wire, which circumstances had not been adverted to by Lieut. Barlow, as this was his first season. Gen. Pasley, therefore, concluded that the firing charges with one conducting wire, instead of two, might diminish the power of voltaic electricity more than had been suspected last year, when this change was introduced so very late in the season, that there was not time to investigate the result of it in all its bearings; and, consequently, he directed that two conducting wires on reels, the same that had failed in igniting a charge when attached singly to less than a twenty cell plate battery, should be attached to one plate battery of ten cells, on the original principle used at Chatham and Spithead, from 1838 to the middle of 1843 inclusive, so that these two wires, well insulated, connected that battery and a charge at the bottom, without trusting to the water. On adopting this arrangement, instantaneous explosion took place as soon as the circuit was completed. Thus the double metallic circuit was proved to be the best for firing gunpowder, whether underground, or under water, and will as such be exclusively used in all future explosions; though for the purposes of an electric telegraph, which requires wires to be laid for many miles, and which needs infinitely less power than is necessary for the firing of gunpowder, water, or moist earth, especially the former, may be used to advantage for completing the circuit, in combination with one wire only, extending the whole length of the telegraphic line.
Civ. Eng. & Arc. Journ.
TRANSLATIONS FOR THE JOURNAL OF THE FRAXKLIX INSTITUTE.
Solar Tides. Extract of a letter from Mr. Airy to Mr. Miller.-—“I beg you to present my best compliments to M. Arago, and to inform him that I have discovered a position on the west coast of Ireland, where the solar tide is greater than the lunar, although upon each side of this peculiar locality the solar is (as usual,) the smaller tide. This position is near a node, and the place of the node is not the same for the solar and lunar tides. A six-hour tide, (marèe quarto-diurne,) which shows itself perceptibly in my discussion of all the tides of the environs, is not influenced by this node, and, consequently, becomes, under ordinary circumstances, the most striking phenomenon; taking all things into consideration, it is the strangest thing that I have ever seen.
Compte Rendus des Seances de l'Academie des Sciences, 16 Sept., 1844.
Printing in Colors by the Typographic Process. M. Silbermann, a printer at Strasbourg, presented several specimens of printing in colors, obtained by the aid of the ordinary typographic press. One of these specimens is taken from an impression of two thousand five hundred copies, “all of which," says the author of the letter, "are perfectly identical with each other; and, after leaving the press, required no re-touching.” This little picture, which presents twelve different colors, was printed by means of a single plate, while, in the ordinary process of polychromatic printing, as many plates are employed as there are distinci colors.
Optical Solar Spectrum. M. Matthiessen presented a memoir, entitled “Memoir upon the optical solar spectrum; upon the improved lentiprism ; upon the absorption of the new extreme violet by different substances; upon the elementary composition of the solar spectrum ; and upon the structure of the eye.
“ I present,” says the author, “ drawings of the solar spectrum, as seen by my improved lentiprism, which is extended beyond the extreme red of the spectrum of Fraunhofer, and adds to it an extreme violet, equal to three-fourths of the whole optical spectrum hitherto known. This new violet part of the spectrum is covered by a great number of obscure rays remarkable, for the most part, for their regular disposition in groups.” Not only do the instruments of M. Matthiessen increase the breadth of the spectrum beyond the photogenic impressions, hitherto obtained upon substances chemically sensitive, but they besides show groups of distinct rays, where the iodized plates produce only dark and shaded bands.
THE FRANKLIN INSTITUTE
State of Pennsylvania
APRIL, 1 8 45.
Connecling-Crank. By ELIJAI GALLOWAY. This machinery, or apparatus, for connecting two shafts so as to cause the same to revolve at different velocities, is illustrated somewhat in the following manner:
Let a b, fig. 1, represent the pitch line of two wheels, the wheel a being twice the diameter of the wheel b; then for every revolution of the wheel a, the wheel b will make two revolutions, and if a tracing point be attached at b', it will describe the straight line a a' upon the face of the larger wheel, and if another tracing point be attached at the opposite side of the small wheel b, such points will describe straight lines at right angles to one another during the revolution of such wheels.
In fig. 2, is shown an elevation of the arrangement of levers for connecting two shafts together, so that they may revolve at different velocities. Fig. 3, is a plan of one of the shafts which is provided with a crank forming a portion of the apparatus. In fig. 2, a is a crank, fixed upon the end of a shaft b, supported by suitable bearings; c is the crank pin which supports the triangular arm d, through each end of which there are pins e e, in the same plane with the aforesaid shast, these pins support two connecting rods' fg, the lower end of the connecting rod f being attached to the crank f', shown in the plan, the lower end of the connecting rod g being attached to the crank pin g' of the plan; b is a pin fixed into the end of the shaft which carries one end of the connecting link i, the opposite end being attached to
Vol. IX, 3RD SERIES—No. 4.-APRIL, 1846.
the centre, or middle, of the connecting rod e, by the pin j; k is the axis of the shaft which is to receive motion from the shaft b, or vice versa ; consequently, if & be double the length of the connecting link i, the point g' will describe a straight line 11, and if we suppose g to be attached at its lower end to the crank pin g', and also the rod f to the crank pin f', and that the axes b and k revolve in suitable bearings, k, will make two revolutions whilst b makes one revolution.
There are other modifications of the above apparatus shown, for which the inventor claims machinery described for connecting axes, or shasts, to revolve in connexion at different velocities.
Civ. Eng. and Arc. Journ.
Accident in a Spinning Mill at Dundee. An accident happened in this town last week at one of the spinning mills, attended by serious consequences; a young man having lost his life, and the person that attended the engine, and several others being severely hurt. The accident occurred in the following manner:-After the engine was started in the morning, and before the