TURF OR PEAT.

When a district is spread out in the form of a flat basin of greater or smaller dimensions, and the water which collects upon its surface or rises from springs, cannot freely escape, but stagnates for a length of time, forming a shallow lake, as is not uncommon in the temperate zones, particularly where evaporation goes on slowly and the atmosphere is habitually moist, as for instance, in Ireland, then water-plants of all kinds, sedges, rushes, reeds, algæ, mosses, more especially Sphagnum, even shrubby plants, as willows, &c., spread from the sides towards the centre of the pool, and quickly form a thick covering of vegetation. With the change of season these plants die and fall to the ground, making room for a second crop in the following spring; this process goes on from year to year, until the shallow pool becomes a bog, and is at length completely filled up with a loose spongy vegetable mass. The remains of the plants immersed in water quickly decay; they lose their original solidity with the simultaneous evolution of gas (marsh gas, carbonic acid) and a disagreeable and noxious smell, while oxygen at the same time is absorbed from the atmosphere and from compounds, such as sulphates, contained in the soil and the water surrounding them, which are reduced to the state of sulphurets. The vegetable matters become brown and soft, and are eventually converted into a blackcoloured, soap-like mass. The debris of plants reduced to this state by decay, or in which the process is still going on, is called turf or peat.

Such is now almost universally acknowledged to be the natural process by which peat has been produced, and the older hypotheses, that it is a formation as old as the hills and valleys where it occurs; a bituminous deposit from the sea; the wreck of once floating islands; or an actually growing vegetable substance, may be viewed as entirely exploded.

The plants from which turf seems to have been principally formed in the northern hemisphere are the mosses, amongst which Sphagnum palustre chiefly predominates. Besides these, heath and fern, rushes and reeds are frequent, and one or more species of cotton-grass (Eriophorum) are also common. Whole trees, oaks, firs, ash, birch, yew and willow, have been frequently found at the bottoms of peat bogs, sometimes erect, as if they had been gradually buried by the encroaching growths of moss, in which

they have ultimately perished, at others lying prostrate, in which position they may have aided in impeding the flow of water and in accelerating the growth of the bog. Human remains have been dug up in turf bogs, sometimes in a state of high preservation, although bearing upon them, in the form of hair clothes and antique sandals, clear intimations of a very long submersion and testifying to the powerful preservative or antiseptic qualities of the turf. Remains of animals now extinct, and fatty substances known as bog-butter, and consisting principally, according to Mr. Brazier, of an acid which he calls butyro-limnodic acid (C32 H32 O4),* support the foregoing statements.

In the southern hemisphere, according to Darwin, peat does not occur nearer the equator than the 45th degree of latitude, and the peat there formed is composed of the remains of almost all the plants growing in the vicinity, including the grasses; it is remarkable, however, that no mosses appear to have taken part in the formation of South American peat, which is chiefly composed of the remains of a plant called by Brown Astelia pumila.

Small deposits of turf are found in almost every country, but districts of immense extent occur upon the low shores of the North Sea and German Ocean (Holland and North Germany), in the formation of some of which, the waters of the sea appear to have borne a part.

In mountainous districts the hollows are frequently filled with peat bogs, the constant assemblage of clouds upon the mountains favouring their growth by a gradual but incessant supply of moisture. These bogs, however, are seldom very extensive, nor does the deposit generally exceed 6 feet in thickness. In Holland entire districts are covered by this formation; in Ireland oneseventh of the whole island, or an area of 2,830,000 acres, consists of peat-moor; and in France, the great marsh of Montoire, near the mouth of the Loire, is said by Blavier to be more than 50 leagues in circumference.

These vast growths of peat are deep in proportion to their extent, the moors of Holland averaging 2 fathoms, while those of Ireland are often 30 feet in depth.

Sometimes the peat formation appears to have taken place at successive periods; the layers are then generally separated by deposits of sand. Although peat sometimes comes quite to the surface, it is frequently covered with sand or mould, but is always found in horizontal layers of moderate thickness. Peat belongs to

*Chem. Gaz. Oct. 1st, 1852.

the more extensively diffused kinds of fossil fuel, and may be distinguished into two kinds, differing in geological age, and in the amount of decomposition to which they have been subject. They are:

1. Recent peat, in which the structure of the roots and stems of vegetables is still perfect, and which possesses a very porous, specifically light texture, is soft and exceedingly fragile. Passing from a light to a blackish-brown colour, and containing the roots and fibres which are really foreign to it, disseminated through an earthy matrix, it gradually verges, without any marked distinction, into the

2. Older peat, in which all organic structure has disappeared, and the fibrous has given place to an earthy texture. Those kinds of peat are considered the oldest, in which the structure has become so fine in the grain, so free from fibre, and so dense, as to appear, when freshly cut, as smooth and shining as wax or pitch. All varieties of peat belonging to this class are distinctly heavier than those belonging to the former; while a cubic foot of the more porous kind only weighs about 4 lbs., the weight of a cubic foot of the latter amounts to from 12 to 20 times as much (Karmarsh).*

The humic acid contained in peat, and observed by Sprengel, as also the various other products of the decomposition of woody fibre, which constitute its chief mass, are of little interest, as regards its application. The same may be said of the resins discovered in it by Mulder, and described by him.

In

Peat is cut and prepared for use in a very simple manner. Ireland, Germany, and most other parts, the surface of the deposit is laid bare by removing the sod or earth above it, and the peat is cut with common spades, or with the slade, an instrument resembling a long spade, with a portion of the blade turned up at right-angles on the one side, into the shape of thick bricks, which are placed to dry, piled up loosely one against the other, or upon

* The grand-duchy of Hesse comprises extensive peat-moors. The Rhine, formerly obstructed in its course at Bingen, was forced to spend its waters over the low-lands opposite Mayence, and the stagnating water which remained after the Rhine had forced its passage through the rocks at Bingen gave rise, in the still swampy district called Ried, to the formation of peat, which is now cut at Pfungstadt and Griesheim. The peat of the latter locality is dense, heavy and black, and closely related to the older peat; that of the former is light, without earthy constituents, rich in the roots of plants, of a light colour, and evidently belongs to the more recent species. The quality of the Griesheim peat is very superior to that from the other locality.

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some kind of support. Care is taken to separate the peat of the upper part of the layer, which is young and fibrous, from the heavy and more plentiful lower peat.

The process adopted in Holland is somewhat more circuitous, but certainly more appropriate, which exactly resembles the preparation of bricks by moulding. The peat is scooped with spades as long as practicable, and when the peaty mass, which is more spongy than solid, becomes too thin to be thus advantageously collected, a particular kind of instrument is substituted for the scoop commonly used upon such occasions. This consists of a kind of sharpened iron ring fixed upon a handle, forming as it were, the side of the scoop; the ring is perforated with small holes on every side, and serves as a support for the bottom, which is formed of a net or piece of cloth. This instrument prevents any quantity of water being scooped up with the peat, the holes allowing the water to run off immediately. The peat-mud collected in this manner is converted into a homogeneous mass by treading with the feet and stirring about with rakes like mortar; the stones are picked out, and it is then spread out evenly in layers of one foot in thickness in large wooden boxes, such as are used for slaking lime, that the water may run off and the mass become dry. To facilitate this, and prevent the adhesion of earthy matter, the bottom of the box is previously covered with hay. After some days, when the mass exhibits a certain consistence, it is subjected to another operation, in which women and children are employed, who, instead of beating it, strap flat boards, like snow-shoes, to their feet, and stamp upon it in all directions. The treading is continued until no impression is produced by a common foot-step; and the peat is lastly struck with beaters until the surface is uniform. The whole cake, eight or nine inches in thickness, is divided by means of long laths into squares of about four inches across. The thickness of the cake corresponds with the length of the bricks. To effect the complete desiccation, the first brick taken out is laid transversely upon the second, the third is laid upon the fourth, and so on; this order is afterwards reversed when the pieces are piled.

In some places, the peat-mud is scooped out with buckets to a dry place, and the water being allowed to drain away, it is made into bricks with moulds. Too much water in the peat may completely destroy its value and render it incapable of being piled.

The value of peat is in proportion to its dryness, density, and firmness. If it possess these qualities in a slight degree only,

it suffers by carriage and by keeping, the upper layers of the heap compressing and breaking the lower layers, which are thus rendered valueless. The porosity and brittleness of peat prevent its application in all cases where the fuel and other matters to be heated are piled up to any considerable height one upon the other.

Dense peat comprises, in an equal bulk, much more combustible matter than porous peat. This fact has led, in recent times, particularly in Ireland, to the construction of presses for the purpose of improving the quality of the lighter kinds of peat, but the difficulty of introducing a machine which is at once rapid in its action, cheap, and effective, has not yet been entirely overcome, the elasticity of the fibre offering great obstacles to the action of the press. It is evident that the use of a press, in addition to the advantages named, would also very much aid the drying process. In one experiment, a brick weighing 8 lbs. lost 2.5 lbs. of water under the press.

Where a large demand admits of peat being prepared upon a manufacturing scale for consumption, the process introduced by Mr. C. M. Williams at Cappoge, in Ireland, has been employed, but we fear without much profit. It consists in breaking up the fibre of freshly-cut turf, placing it thus broken between cloths, and submitting it to the action of a powerful hydraulic press. The peat on leaving the press occupies only

of its previous volume, and has lost about of its weight from the water which has been expelled. It is then denser than wood, although prepared from the lightest varieties of peat, and is said to have no tendency to reabsorb water. The cost of the process is not considerable, as the prepared peat can be delivered at 58. per ton; the price of the unprepared material in the neighbourhood of the moors being 3s. 6d. per ton.

The longer peat is kept and allowed to dry in suitable sheds, the more it will improve as a heating agent. The spongy character of peat enables it to retain a large but very variable quantity of hygroscopic water. Karsten observed a loss of as much as 45 per cent by simply drying freshly-cut peat in the air, but even when thus dried the quantity of moisture retained varied between 25 and 50 per cent, which could be driven off at a higher temperature. The specimens examined were however probably in the latter case not fully dried, and in this state the peat is principally consumed in this country and in Ireland, creating as it must a loss of heat equivalent to 30 per cent. Under