New Series, of the promised regular assistance of Mr ROBERT Christie, the Secretary of the London Mechanics' Institution, whose well known acquaintance with physical science, as well as the practice of Mechanics, eminently qualifies him for the task.

The first number of the New Series will be published on the 10th July next, price four-pence, and be continued on every succeeding tenth day; namely, on the 10th, 20th, and 30th of each month. On the last day of the month, the three numbers will be put in a neat wrapper, and form a REGULAR MONTHLY PERIODICAL, price one shilling, which will be delivered in the country on the first day of every succeeding month. With the view of distinguishing its title from that of a respectable contemporaneous work, which was commenced subsequently to it, it is determined to alter the title of the New Series to

REGISTER OF THE ARTS, AND JOURNAL OF PATENT INVENTIONS;

in which will be exhibited, the progressive improvements made in every branch of practical mechanics, including the earliest description of every new patented invention of utility or importance; the whole of which will be illustrated by numerous clear engravings, mostly made from original drawings by the Editor.

The want of sufficient space, to do justice to the admirable lectures delivered at the London Mechanics' Institution, will oblige us to omit inserting reports of them, (except occasionally such parts as may relate to any new scientific fact, or to the description of any new machine ;) but the members, and our readers generally, may depend upon a faithful and regular notice of its proceedings, and for the timely announcement, of all the arrangements made for lectures and other business, by anticipation. The New Series will likewise contain a similar periodical notice, of the proceedings of all the other Scientific and Literary Institutions of the Metropolis: these notices will be uniform and concise, and placed under one head; and will, we trust, form a body of pleasing and convenient intelligence, to a great body of our Subscribers.

Mc. CURDY'S PATENT

"FRANKLIN DUPLEX STEAM GENERATORS."

THE inconvenient size, great expense, and personal hazard attending the use of the ordinary boilers to steam engines, have of late years excited the attention, and employed the talents, of many scientific and ingenious men, to devise a less objectionable mode of generating steam; numerous have been the plans proposed to effect it, and some degree of merit has (as far as our observation has extended) been due to most of them. The efforts of the several inventors and patentees, who have of late years put forth their contrivances before the public, seem to have been uniformly directed to one point, viz. the exposure of the smallest quantity of water to the largest heated surface, at that particular temperature which will generate the steam most economically, and at the same time of sufficient elastic force. Vast sums of money have been uselessly expended in attempting to accomplish this important desideratum, attributable, we believe, not to the want of mechanical skill or intelligence, but to the deficiency of accurate chemical data, whereupon ingenious men might safely exercise their talents in the construction of suitable apparatus. The invention we have now to describe consists of a series of double tubes, placed one within another, which are arranged in any required number in a furnace of sufficient capacity, with the spaces between the exterior and interior tubes filled with water, by which a very extended and thin volume of water is exposed to the influence of the fire. The specification, from which we derive our information, being before us, we annex the following extracts from that document, as sufficiently explanatory of the details.

"My invention of certain improvements in generating steam consist in a new combination of materials, or the adaptation and application of old and well known substances to produce or effect a particular purpose; which is both novel and useful, and which from their form I denominate Franklin Duplex Steam Generators.' For this purpose, I construct one or more vessels or tubes of any given number, length, or diameter, proportionate to the size of the engine, or quantity of steam wanted, made of wrought or cast iron, or other material of sufficient strength; which tubes or vessels are closed at both ends; on one end of each of which a head is fixed, that can be taken off at pleasure. Inside of each of these vessels or tubes I insert, or suspend in the centre, another vessel or tube of still smaller size, of similar materials, leaving a small space on all sides, varying according to their size from one quarter of an inch, to one inch and a half (according to the station they occupy in the furnace, near the fire or more remote) which is thought sufficient for the generators attached to an engine of the largest size: between the outer and inner tubes or vessels. The inner tubes or vessels are rendered steam tight, and closed at both ends, except such number as are placed within the reservoirs or steamometers' as I term them, and which are intended to contain a body of steam for the supply of the engine: or the minor tubes or vessels may be omitted entirely in this combination in the

steamometers or vessels intended to contain the steam. I place these tubes or vessels thus arranged, which I term duplex steam generators, in a common heated furnace in the same manner as gas retorts, or in the most advantageous manner for heating. The tubes or vessels at the top, or next communicating with the engine, are the most suitable to be reserved for the reservoirs or steamometers, and which I should generally make to contain about ten times the solid contents of the working cylinder of the engine. The outer or exterior vessels or tubes are connected by pipes leading from one to the other, which connecting pipe ought to lead from the upper part of one tube to the upper part of another, through which the steam and water rushes, from the time it is injected by the forcing pump, which I use to supply them with water till it passes into the steamo. meter, and from thence through the eduction pipe, which I insert into the lower part or bottom of the steamometer (whereas in boilers the steam is carried out at the top) into the engine. Into each of the interior tubes or vessels (closed at both ends) may be inserted small pipes, passing from the inner tubes or vessels through the outer ones into the open air, to permit any water or steam that might be forced into the inner vessels or tubes by the pressure of the steam, to escape. To keep the interior tubes or vessels in their places, and at equal distance from the outer ones, I put around them spiral bands, extending the whole length of the inner tubes or vessels, or rings at intervals, of from one to two feet apart, or pins of the same thickness as the space intended to be preserved as a water line; these rings are grooved all round, or have holes drilled in them to permit the free passage of the steam and water; and if the heat should cause the outer tubes or vessels to warp or yield, the same distance will always be preserved between the outer and inner tubes and vessels, and also prevent them from coming in contact in any part. A number of the duplex generators' may also be connected with the common boiler, for the generation of steam, the water being forced through them by the pump, and discharging into the steam chamber of the boiler in lieu of the steamometer.

"In the preceding engravings, Fig. 1 represents a front view of a furnace containing five" duplex generators," a 1, 2, 3, 4, 5, and one "steamometer" b. Fig. 2 is a view of the opposite end of the same furnace, with the cast iron plate which encases it broken away, to shew the interior of the furnace, the hemispherical ends of the tubes, the communication from one to the other by means of short bent pipes, and the manner in which the fire acts upon them when so placed; the letters of reference designating the same parts in this figure as in all the others. Fig. 3 represents a cross section of the outer tube of a " duplex generator," and one of the hemispherical ends of the inner tabe, with the space or "water line" between the two, preserved at a uniform distance apart by the interposition of narrow pieces of metal. Fig. 4 is a front end view of a ometer," with the flanch removed. Fig. 5 is a horizontal section of two" duplex generators," and one" steamometer" between them ; in the former, the interior tubes c c are not shewn in section, but

"steam

whole, that it may be seen they are perfectly closed at each end, from which the water is compelled to assume the shape of a hollow cylinder. In the "steamometer" b, the interior tube d is left open at one end, for the steam to enter and become a reservoir for the supply of the engine.

"eis the water-pipe leading to the pump; fthe pump; g the steam or eduction-pipe, leading from the "steamometer" into the engine. The mode of operation is as follows: each stroke of the pump introduces water into the vessel, a 1, (by the pipe e), which is forced or distributed around the spaces between the interior and exterior tube, termed the "water-line," in all the vessels. The steam generated in this first vessel, and the water that remains, is next forced through the connecting pipe into the second vessel, a 2; from thence successively through a 3, a 4, and a 5, then into the "steamometer" b, by the end always open; and from thence by the eduction-pipe g into the engine. The water injected by the pump at c has thus, in its passage from the pump to the engine, passed in a thin sheet over a heated surface of many thousand inches, and consequently the steam may be generated of a very high pressure with extraordinary rapidity.

"The patentee claims as original, First in the generators,' the combination of the materials, or tubes or vessels to produce the desired effect, by inserting or placing one vessel or tube within the other, in such a manner as to expose a small quantity of water over a large heated surface, by leaving a very minute space or passage between the outer and inner tubes or vessels, the whole length as well as the two ends. Second: He claims as original the leaving open one end of such number of interior tubes or vessels as may be necessary in the steamometers or reservoirs for steam to produce the desired effect. Third: He claims as original the steamometers,' or separate vessel for containing the steam, with the eduction pipe placed in the lower part to prevent the possibility of any accumulation of water. Fourth: He claims as original, in this combination to produce the desired effect, the rings, or spiral bands around the inner tubes or vessels, or pins filling the space at intervals between the outer and inner tubes or vessels, to produce the water-line. The advantages of this plan are, that the water being distributed in a thin sheet over a great heated surface, and exposed to the almost immediate action of the fire, in the duplex generators, the steam is generated with immense rapidity; there is no collection or body of water as in a boiler; they occupy but a small space, and consume but little fuel, in proportion to boilers, to produce the same power; the steam may be generated to the greatest height, and the power increased at pleasure, without danger."

Remarks by the Patentee." In consequence of the small space between the outer and inner tubes or vessels being always preserved, there can be no accumulation of water, the current being constant along the water-line; nor would the diameter of the generators cause any difference in this respect, the water-line being so minute and uniform. The generation of the steam is rapid and instan

*