554 THE COLLIERY GUARDIAN. March 24, 1916. motions. The coke is pushed out through quenchers to an inclined hearth, over which it passes ;o 36 in. tray conveyors delivering the product to a central screening station, and thence to the blast furnace wagons. Gases from the ovens are collected in a large main, and exhausted through air and water condensers, then passing through tar extractors, and scrubber washers for absorption of benzol and remaining ammonia. After this treatment the gases are utilised,, half for heating the flues of the coke ovens, and the other half, in the, steel works. Tar, ammonia liquor, and benzol extracted from the gases are run into storage tanks and treated in buildings ■ / . • - ■ V,*„ m-- r-' & Fig. 2.—Coal Washery Building from the North-east. Coal Washery O/R7 HOPPER. I V/A ■M Fig. 3.—Section of Coal Washery. situated between the coal washery and the batteries of coke ovens, quenching and cooling water used in con- nection with the recovery of the by-products being drawn from the ferro-concrete tank over the washery building. Institution of Mining and Metallurgy.—The report for 1915 states that over 600 members (more than 25 per cent, of the membership) are serving with H.M. Forces, and reference is made to the large number of military decorations and other distinctions won by its members, particularly by those serving in the Royal Engineer tunnelling companies. During the year 72 members were admitted, raising the total to 2,441. The accounts show the ordinary receipts for the year ended December 31, 1915, to have been £4,906, as compared with £5,090 in the previous year. The ordinary expenditure amounted to £4,666. In consequence of the war, the council decided not to make the usual awards of medals, premiums, and post-graduate scholarships. For the same reason, the post-graduate courses were also held in abeyance. Sir Richard A. S. Redmayne has been elected as president, in succession to Sir Thomas K. Rose. PIT TIMBER AND ITS PRESERVATION.* By Percy Groom, M.A., D.Sc. The wastage of timber in coal pits that is caused by decay is very great, in fact, far greater in this country than is generally realised. In mines in the United S. ates it is estimated that of the whole wastage of timber 50 per cent, is due to decay and insects, mostly the former. The decay of wood is usually caused by wood-destroy- ing fungi. The first step is the infection of the wood, either by means of microscopic spores wafted through the air, or by the body or Mycelium of the fungus advancing from already infected material. In either ease, fungal threads entering from the mtside penetrate, grow within, and gradually permeate and destroy the wood. Spores are produced in myriads by easily visible fructifications, -which assume the forms of mushrooms, bracket's, or sheets. Consequently one method of decreasing infection is to destroy these fructifications before they have produced or shed their spores. Such a collection and destruction of fructifications in coal pits may sometimes be impracticable, and even when executed, its efficiency may be under-estimated; but by this simple me.hod the tender fungus was practically exterminated within a few years in a large forest in Germany. Before this method is attempted, it is essential to know which fungi are doing serious damage in coal pits, and therefore to identify the various fungi present. Unfortunately, many kinds of fungi readily produce spores quite apart from such fructifications, whose destruction might therefore be relatively futile. It is therefore necessary to work out the life histories of the fungi present in coal pits; and we may then also learn how to prevent or decrease the production of spores. Infection may take place by threads of the fungus advancing from an infected to a sound piece of wood. According to their mode of growth, wood-destroying fungi may be ranged in two groups. In one group the fungus, having established i.self at a point in the wood, not only gradually grows within the wood, but also emits threads that emerge from the wood, grow rapidly over the surface, clothing this with growths, often white, that are shaped like swings, sheets, or cushions. These superficial growths in turn send threads into the wood, and thus feed upon it. Especially by means of these exposed string-like growths the fungus can pass from one piece of wood, through dirt or even brick walls, over stones, coal, or iron, and can infect a sound piece of wood yards away. Fungi of this kind are very familiar in certain coal pits, and are locally known as “ cotton thread fungus.” Mining engineers will at once call tc mind a number of the ordinary operations in coal mines that seem incidentally to transmit infection to sound wood from timber already attacked by fungi of thi- group. In the other type of attack the fungus advances more * Paper read before the Midland Institute of Mining, Civil, and Mechanical Engineers. slowly, for, having entered the wood, it steadily eats its way in the interior, and keeps at a certain distance from the outside. Wood infected by such fungi, especially .when it is discoloured by various agencies in coal pits, may show no appreciable external sign of its rotting condition, even when a shallow incision is made with a knife. This type of attack is certainly abundant in coal pits, and where it alone occurs the miner may readily, but wrongly, assume that his pit is free from decay. Here and there the fructifications of such fungi will be.ray the secret. These considerations suggest that in a coal pit where the swift-growing fungi of the first group are present, the durability of the timber may be considerably increased by rendering the surface of the wood resistant to infection; bu. that where decay is largely due to the stealthy, slow-growing, internal fungi, decreased loss may often be more easily secured by destruction of the fructifications. The statement is frequently made in reference to certain coal pits that there is little or no loss due to decay of wood. Facts just mentioned suffice to prove that such statements cannot be accepted without fuller investigation, even when the rupture of pit props appears to take place while these seem to be perfectly sound. In pits that are dry, or where the mine water is very rich in salts, there may be little or .no decay; and where props are exposed to great pressures they .rupture while in a sound condition. Yet, if it be found that there are coal pits free from decay whilst showing conditions essentially similar to other pits in which decay is rife, then we arrive at the fundamentally important con- clusion that the decay of wood in pits can be checked by the cheapest of all means, namely, sanitation of the simplest kind. It is therefore evident that we must acquire by investigation a thorough knowledge of the conditions prevailing in coal pits, and this becomes doubly clear by a consideration of the effects of external conditions on the growth of wood-destroying fungi. For the purpose of respiration, such fungi require a free supply of air, and particularly of oxygen, but they also demand an adequate supply of water. It is, there- fore, clear that wood, either very dry or very wet, is generally safe from decay. When very dry, it has the air, but not the moisture required. When waterlogged, it lacks the requisite amount of air.* These facts, partly at least, account for the practice adopted in some countries of drenching the wood with water regularly, and for the circumstance that wood under an unceasing flow of water in coal pits is generally durable. As fungi will attack wood only when this contains more than a certain minimum and less than a certain maximum of water, we can understand why decay is often more pronounced along the return draft than along the intake way, and why, in relatively dry mines, decay is worst in the wettest places, whereas in moist pits the reverse is the case. Different kinds of fungi vary as regards the degree of dryness or wetness of the wood that they can success- fully thrive under. One species, Merulius lachrymans (causing the worst form of dry rot in buildings, and probably active in many coal pits), when once estab- lished can attack the driest wood. In respiration, this fungus produces water in sufficient quantity to render the infected wood moist, wet, or sodden. It thus renders the wood liable to attack by other fungi that demand more water; indeed, in a relatively dry mine the extermination of Merulius alone might indirectly thus lead to the extirpation of some or all the other kinds of wood-destroying fungi present. This case again emphasises the necessity for investigation into the con- ditions of existence of fungi living in coal pits. In order to protect wood against decay, it is sufficient to keep it absolutely dry or soaking wet. Apart from the practical difficulty of keeping wood in pits wet, it must not be forgotten that wet wood is much weaker than dry wood (sometimes having only one-third the strength). On the other hand, at present it is not economically practicable to prevent the ingress of air or moisture into pit timber, for continuous impervious coatings are diffi- cult to secure and maintain. Consequently, the pro- tective effect of seasoning wood before use in coal pits is determined by the dryness or wetness of the mine. If, for instance, pit props be barked and then seasoned, their superficial dryness tends to protect them from decay so long as they remain thus dry: but wood is hygroscopic, so that in wet mines such props soon relapse into their former moist and vulnerable condi- tion. On the other hand, if unseasoned props, with intact bark, be utilised in relatively dry mines, the intact bark acts as a shield against infection; but as the wood slowly and gradually dries, it shrinks, and in the bark there arise cracks, through which infecting spores gain entrance to the relatively moist wood within. These considerations supply an explanation of the contra- dictory results obtained in the United States, where barking the props was found to increase their dura- bility in dry mines, but not in wet mines. In our own country the collection of statistics as to the relative humidity of the air in various coal pits would give valuable indication as to the extent to which seasoning and balking, or the latter alone, would serve to preserve pit props. The seasoning and barking would not only directly increase, but also prolong the strength of props: and the significance of these facts may be especially great in the case of deep pits. Yet dryness to some extent favours the production of fructifications, and consequently of their spores. Hence, such fructifications are often more developed along the intake ways than along the return ways; * Some woods decay relatively rapidly under water : the extent to which very wet wood in mines is destroyed by bacteria, and the extent to which the latter are responsible for the production of marsh gas (firedamp) are unknown, and call for investigation.