The specification then goes on to describe the manner in which the plates shall be cast or moulded, and also in forming the curves or cellular plates, while it is to be observed a considerable saving is to be effected in the increased durability of the boiler, which in itself is a very important consideration.

We deem it unnecessary further to follow out the specification of the patent, being content with drawing attention to an improvement whereby great economy may be observed in the working of our mines and manufactories, the patentees undertaking to guarantee a saving of at least 25 per cent. on the fuel previously used by the ordinary boiler; at the same time, by getting an increased power in a reduced space, a considerable saving is not only effected in the construction of the machinery, but also the space occupied, which, with the saving in fuel, form most important features as connected with steam navigation. The diagram we have introduced will best illustrate the nature of this economical and vast improvement in generating steam.

PROCESS OF CARBONIZING TURF WITHOUT CLOSE VESSELS,

The Peat furnishing its own Caloric, without producing Ashes. BY DOMINIQUE ALBERT, LL.D.

WHEN, in 1835, I built my present works at Cadishead, I was chiefly induced to choose the place on account of the proximity of both turbaries, Chat Moss and Barton Moss, having previously ascertained that I could make with turf as good charcoal as with wood.

As the charcoal I wanted was for some chemical purpose other than to be used as fuel, the first condition of the carbonization was, that it should produce a vegetable black, free from the mineral substance mixed with it, as is always the case when turf is carbonized in Ireland, to supply the hearths of some country smithies. I began, then, by submitting the turf to a dry distillation in iron retorts, five feet deep to four feet diameter, covered with strong sheet-iron caps, to which I adapted cast-iron pipes. I soon found, however, that the quantity of auxiliary mineral fuel required to burn the turf, owing to the distance of seven miles from the nearest pits, rendered this method too expensive to be continued.

I expected that the acid would compensate for the price of the coal, but I could never get it above two or three degrees; besides,

the pyrolignous alcohol diluted in the acid existed in a very small proportion. The tar, which was comparatively abundant, contained the greater part of the spirit; but the low price of tars in general offered me no encouragement to proceed.

I knew, by the discoveries made by my countryman, Mr. Merle, in 1834 and 1835, that certain species of turfs gave a richer and superior gas than either coals or oils, and I convinced myself that the peats in my neighbourhood were of an excellent quality for such a purpose, but I did not feel inclined to set up any apparatus to save that produce, so I turned all my attention to find a cheaper mode of producing pure charcoal.

I had latterly observed the Irish in their process, which consists of setting fire to a few turf cakes placed on the ground, so as to let the air play between. As soon as these cakes are burning, they heap round and above other cakes, which very soon ignite also. They continue to feed thus this heap of fire, till it reaches about five feet in height, and six or seven at its base. They let it burn until the whole appears in a complete glow, when they cover it with large wet sods, either of soil and grass or heath sods, from the surface of moss land. This careless, but cheap and easy manner, causes the charcoal to be mixed with a quantity of uncarbonized vegetable, marl, sand, stones, and a notable proportion of ashes, all matters which do not affect the iron jobs with which they come in contact.

The Dutch I saw, many years ago, carbonizing peat for domestic purposes, in small conical furnaces, as common with them in the country places as the bread ovens are here. They light the turf from below; and, when the combustion is nearly completed, they close the top and bottom. Their method, though superior to the Irish, and well adapted to their object, is neither as complete, nor does it give so pure an article as I wished; besides, I found its application almost impossible on a large scale.

Amongst the different plans and instructions I consulted to assist my experiments, I gave the preference to a large round perpendicular furnace, in which, according to Dumas (Chemistry applied to the Arts), Mr. La Chabeaussiere distils wood.

After having studied what modifications were necessary to render Mr. La Chabeaussiere's furnace useful for peat's carbonization, without saving either gas or liquids, I constructed the following kiln-On a solid soil, I made an excavation from ten to twelve feet wide at the top, nine feet deep, and nine in diameter at the bottom, which I covered with a dry brick floor, that had a convexity of six inches. I lined this hole round with a dry brick wall, in the way of a common pump pit. At four equal distances at the bottom of the round wall, I opened an air-hole of about four inches square, and continued it in the form of a narrow chimney outside the wall, to the height of about six feet, when I prolonged

it about six feet more, but in a horizontal direction. For the top of this kiln I had a sheet-iron cover made, a few inches wider than the diameter of the brickwork, of a convexity of two feet, with a round hole or chimney in the centre, one foot high, and nine inches diameter, provided with a cover and handle similar to that of a canister, and at a foot from the extremity of the large cover, are cut out four auxiliary chimneys, at equal distances one from the other, with a four-inch diameter. Four strong iron rings are fixed to the cover to receive the hooks of a chain, which, by means of a double purchase, raises or lowers the cover.

When this furnace, says Dumas, is filled with wood, the cover is lowered down, and some firebrands are precipitated through the central chimney to the bottom of the kiln; the wood being placed so as to leave a sort of funnel open. By means of the four blowing air-holes, the fire is very soon spread in all directions, and its progress is to be regulated by shutting or opening the smoke and air-holes, according to the direction of the wind.

These rules, which no doubt did answer when wood was to be distilled, were inefficient when applied to the carbonization of peat; but by dint of trials and patience, I succeeded beyond my utmost expectations, upon the following plan:

I make two tunnels of inch board, nine feet high and eight inches square, with some hand-holes from distance to distance. These tunnels I place in the kiln along the side, in order that the bottom end may correspond with one of the four air-holes ; one of my workmen descends then to the floor of the furnace, and forms an aerated bed with peat, by setting the cakes upright, with their tops inclined one towards another, so as to create a good draught, which must, as much as possible, run in the direction of both air-holes where the tunnels are standing. It is necessary for this operation that the cakes be entire and dry, as pieces would intercept the air, and a wet cake would paralyze the action of the fire. After the setting of this bed, the peat is thrown down upon it, and left in the natural confusion of its fall, only it is required that a man place round the tunnels the turf cakes in regular order, to build like a chimney round these moveable tubes. When the kiln is filled and heaped up about three feet above the level of the hole, the tunnels are drawn out by means of their hand-holes, and leave two square passages from top to bottom. In these temporary chimneys, a few incandescent peat cakes are thrown, and on these some broken pieces of turf, till the passages are filled; but as the air plays more freely through these former chimneys, some barrowfuls of peat crumbs will shut the too wide pores, which places are easily seen by the greater volume of smoke escaping from them. The kiln left open, to facilitate a more general conflagration, is not covered before the heap of turf cakes has sunk to the level of the brickwork. In this state, the cover is let down, and some soil is brought round

its border to intercept the escape of smoke. In this stage of carbonization, all the air-holes with the large and small chimneys are open.

As soon as the fire is perceived through either of the small chimneys corresponding with the passages where the fire has been lighted, the horizontal mouth of the same air-hole is to be shut with a piece of brick and some marl, and the others are to be successively stopped in the same way, the moment the redness of the fire can be distinguished. If there remains any doubt of the perfection of the operation, a pole about fourteen feet long should be thrust through the hole where the carbonization appears incomplete, and by thus gauging to the bottom of the furnace, you will immediately be aware of the state of the charcoal, which you can remedy instantly, by opening the air-hole opposite the place examined.

When the smoke begins to abate, you place the cover on the central chimney, but so as to shut only the half of the aperture, taking care at the same time to direct the open part of the cover towards that part of the kiln which you might consider not so perfect as the remainder. At last, when the eruption of smoke has ceased, you shut all chimneys immediately, and the operation is at an end. It requires generally twenty-four hours to complete the carbonization of one furnace, and sixty hours for carbonization and cooling of the charcoal. A kiln of these dimensions can receive between three and four one-horse loads of peat, of about fourteen hundred-weight.

There are three kinds of peat. The white, or top of the moss land, is the lightest, and consequently the worst; it is sold from four to five shillings the load. The brown, which comes from the second stratum, is much better, being more compact, and sells at five shillings and sixpence per load. The black, or best quality, sometimes called iron-turf, is very hard and heavy; it gives an intense and sharp heat; produces a thick black smoke, with strong and unpleasant smell; it burns slowly, and is bought at six shillings. The incineration of the black turf leaves heavy reddish ashes, whilst those of white turf are of a sulphur yellow, and those of the brown have often a sort of orange tinge.

The peat ashes which owe their alkaline quality chiefly to the presence of lime, are considered a good manure for grass and clover, and used as such in the north of France and in Belgium. March and April are the best months to use them. They are generally sown during damp weather, and will have a good effect used with any plant, at its first appearance above ground. I tried them last year with pease and other vegetables, and perceived in one instance, that the use of them cleared the cabbage plants of the insects that were devouring them.

In order to get the kiln to act more regularly, it is well to carhon each sort of peat separately. I have at present four