HUTCHISON'S PATENT GAS-GENERATOR

FOR THE USE OF SHIPPING.

In constructing this apparatus, it has been the object of the inventor to introduce a convenient and economical method of supplying a first-rate ship of war, or other large vessel, by one and the same process, with abundance of fuel, light, and heat.

Description:

a, is the furnace; bb, reverberating draughts; cc, retort; aaa, section of a cone furmed of sheet-iron; ee, dry lime purifiers; ƒ, gas-pipe; g, a hydraulic or sand-joint; h, a cast-iron cover; i, chimney. The coals from which the gas is to be extracted are placed in the retort. The distillation is effected by the action of the hot-air produced by the ignited coke in the furnace; this hot air, by traversing the passages shown by the arrows in the centre cone, distributes a uniform heat to every part of the retort. The gas, as it evolves, passes through the purifiers ee, and deposits all its impurities in the layers of lime spread upon the shelves,

It is likely to strike any one upon a first view of this machine, that a considerable addition to the usual cargo of coals would be necessary to its working on board ship; but the contrary is the case, as the same stock of coals, after having supplied gas for cooking and lighting, and diffused warmth through the vessel, will actually yield one-fourth more than its original quantity of coke: hence, there is a decided increase of fuel after having obtained from the coals the already enumerated advantages.

The saving which will result from adopting this contrivance in the Royal Navy and Merchant Service will be considerable, especially with respect to oil, candles, fire, wood, and coals.

The gas-generator appears to be peculiarly adapted to those vessels that trade to India and the Tropics, as it is well known that passengers (particularly invalids) are subjected to great inconvenience from alterations of temperature, which are frequent during such voyages. Those evils may now be, in a great mea-sure, remedied, by regulating (through the supply-valve) the exact degree of warmth deemed necessary for the health and comfort of the passengers; and, by the same means, the gas in the galley,

or caboose, can be immediately ignited, gradually reduced in quantity, or instantly extinguished; and these processes will create neither smoke, ashes, nor offensive vapour.

The gas may also be very effectively employed in making signals: the flame may be enlarged to any required dimensions, and, with a little care on the part of the attendant, it will exist in defiance of wind and rain. A powerful light to distinguish the admiral's ship is a matter of the utmost importance during war, or when a storm has dispersed a fleet,

A gas-light of sufficient size placed at the bows of the steamers employed on the Thames, would render the navigation of the crowded parts of the river much easier and safer, as it is well known that the majority of accidents which have happened of late years on the river, are to be attributed to the defective condition of the bow-lights. This apparatus will also be useful in cases of shipwreck in saving the lives of individuals.

Air and water-tight vessels constructed of caoutchouc and inflated with gas, will, by judiciously attaching them to the gunwale of a boat, effectually prevent her from swamping, and enable her to ride through the most tempestuous sea.

The apparatus occupies about three feet six inches square, and six feet in height.

To guard, hospital, convict, or prison ships, this machine will be exceedingly beneficial, both in respect to economy and comfort.

Light-houses may also by the same process be illuminated at half the present cost. To this latter application of his contrivance, and to a method of carrying on telegraphic communications during night, Mr. Hutchison has devoted much of his time; his attention is at present engaged upon the subject; and after he has matured his plans and calculations, the results of his investiga. tions are to be laid before the public.

London, March 11, 1836.

C.

CORNWALL POLYTECHNIC SOCIETY.

We have before spoken of this Society in terms of high praise; and judging from the third Annual Report, which it has just issued, it has worked hard to make good its title to the rank we as

signed to it of being one of the best, if not the very best of the institutions of its class. Agreeing, as we do, in a great measure with our correspondent P. P. C. R., (No. 660,) that the number of permanent Scientific Institutions and Museums is very small, we are the more delighted to observe the strong indications of lasting prosperity and usefulness evinced by our Cornish favourite. Patronised by the King, and having upon its roll of officers some of the first scientific names in the country, and others of the highest local influence, science cannot but continue to flourish under its protecting and fostering care; and more especially, while its managers continue to follow out the sensible plan of operations avowed in their present report.

"The principal cause to which your Committee would attribute the success of their past proceedings, and the quarter to which they would chiefly turn for hopeful encouragemente in the prospect of the future, is the adaptation of the society to the tastes, habits, employments, and capabilities of the country. But for this, they durst not anticipate any thing beyond a brief and ephemeral popularity. No sustained and permanent result should be hoped for from any mere adventitious stimulas.'

Cornwall, as all the world knows, was the nursery of the steam-engine. The vast quantity of water which had to be raised from its many valuable mines, in order to keep them in a workable state, prompted and rewarded the exertions of Savary, Newcomen, and Watt; and this district still claims a great superiority in its engines over every other. The reported results have, it is true, been received with incredulity in some quarters; and the alleged superiority has been stoutly questioned, if not absolutely denied. We have, for our own parts, however, no doubt whatever on the subject, and look upon the facts stated in the fol lowing brief historical summary, by Mr. Enys, as not only indisputably established, but quite scientifically accounted for :

"The mode of estimating the performances of steam-engines, by the number of lbs. lifted one foot high by the consumption of a bushel of coal, was introduced into Cornwall by Watt, when it became requisite to keep a regular account of the work done and coal consumed, for the purpose of calculating his share, which was one-third of the saving of coal effected by his engine in comparison with Newcomen's.

"The performance of two atmospheric en gines, at Poldice, had been ascertained as a standard of comparison, and declared by a Committee: for convenience the present dynamic unit was afterwards adopted, and the work done when thus expressed was equal to 7,037,800 lbs. lifted one foot high by each bushel of coal. A dispute arose in 1798 between Messrs. Boulton and Watt and the mining adventurers in Cornwall, and it became necessary to ascertain the average duty, which was proved to be 17,671,000 lbs.: this was rather less than in 1793, when the average of seventeen engines was 19,569,000 lbs. After the expiration of the patent in 1800, no accounts were kept of the work performed by the engines under the direction of the mining engineers.

"In August, 1812, the average duty of several engines on a month's trial proved to be only 13 millions, and the truth of the prevailing opinion became apparent that less work was done than during Watt's patent. The present monthly report of work per formed' was then established under the management of Mr. Lean, and since his decease has been conducted by his son, so that there exists a series of reports for twentytwo years, showing the duty for each month of the large engines employed in Cornwall, including the size of the pumps, and their depths, number of strokes, bushels of coal consumed, &c. &c.; a reference to which would point out at what period, and by whom, every increase of duty was obtained.

"Woolf introduced the use of high-pressure steam worked expansively in two cylinders, and first succeeded in performing fifty millions. Other engineers worked high steam expansively in one cylinder, which plan became general on the introduction of Trevithick's cylindrical boilers.

"Several engines now constantly perform a duty exceeding 70 millions, double that of the best of Watt's, and of which one has reached 91,200,000; another mentioned last meeting by our President, averages about 90,000,000; its best performance was 97,800,000, for one month.

"Part of the increase of duty must be attributed to the improved pitwork; the most rapid increase, however, took place on the introduction of a most complete system of clothing, the present practice of which is so efficient, that in two instances, though the steam in the jacket was at least 270°, the outside casing did not exceed 78°;—the thermometer was covered by a silk handkerchief to prevent the draught of air in the enginehouse affecting the results;-the air outside was in one experiment 56°, and in the enginehouse, about 660;-the surface of the ashes over the boilers was about 900,"

The preceding extract is introductory to a set of tables, by Mr. Enys, "relative to the properties and practical application of steam, which are of such general interest, and calculated to be of such extensive utility, that we need make no apology for transferring them, along with some further preliminary remarks, to our pages.

"The simplest form of calculating the moving power of steam, is the extension to all pressures of the mode employed by Tredgold for the power of steam of atmospheric pressure. The term efficiency used in these tables, was suggested in a paper published in the Transactions of the Royal Society, in 1827, by Mr. Davies Gilbert: this word prevents confusion with engineer's power, or horse power, which is available efficiency, or the neat power of the engine applicable to the owner's use. It is equivalent to "The power of steam to produce motion" of Tredgold; "The power exerted by steam" of Wood on Railways; "Mechanical power of steam." A similar distinction is also required between the gross work, including inertia, friction, &c., and the neat work done. Effect may be applied to the former; Duty to the latter.

Efficiency. (Force and Space.)

We are glad to observe, that among the premiums offered through the medium of the Society for the current year, (and very liberally "not confined to the county,)" there are two by Mr. H. H. Price, C. E., "for the best, and second best practical plans for adapting to steamvessels" that method of working steam expansively, the advantage of which, is so strikingly demonstrated by the preceding tables. It is accompanied, however, by this very proper caution, that "due regard must be had to the essential difference between a single-acting engine working pumps by a lever, and two double-acting engines working with a crank."

The premium offered last year by the Society, for the best method of measuring the length of the stroke of the piston, has been awarded to a counter invented by Mr. M. Loam, which is about to be introduced in the United Consols mines. This apparatus is admitted, however, to have two serious defects; in the first place, it registers only the number of

necessarily the space through which it strokes made by the piston, and not passes; and secondly, it derives its motion from the bob through a lever, so that it measures the arc of a circle instead of the tangent to it; in other words, it shows the distance passed over by the end of the working beam instead of that travelled by the piston. Something much better is therefore still wanted.

Another of the steam-engine desiderata of last year was an exact method of "measuring, and registering the exact quantity of water supplied to the boiler." This is now considered to be fully supplied by the water-meter of Captain T. Richards, of Wheel Vor, of which a drawing and description are given in the present Report. The principle on which this meter is constructed is that a vertical measuring pole, and the parts connected with it, shall be thrown out of action whenever the feed is turned off, but driven down and forced up by the water whenever it is passing into the boiler, and that this shall not take place ing the quantity delivered by showing the without acting on a counter, and registernumber of inches the pole has gone over in its down stroke. Mr. Richards proposes that the measuring pole should be of such diameter that the cubic content of every inch in length should be equal to a quart of water, in which case the indications of the counter would be in quarts. In this plan there are no additional valves