March 24, 1916. THE COLLIERY GUARDIAN. 555 moreover, repeated drenching of wood tends to check the production of such fructifications. The relatively high temperatures prevailing in coal pits accelerate decay, since, so long as sufficient moisture is present the activity and growth of the fungus are (within limits) proportional to the tempera- ture. But each species of wood destroying fungus grows only within certain ranges of temperature. For instance, Merulius lachrymans may be found growing in mines whose temperatures lie below 80 degs. Fahr., but not in deep coal pits whose temperatures exceed this. Of greater practical importance is the fact that exposure to high temperatures, especially associated with moisture, serves to kill fungi and their spores. Thus it is easy to sterilise pit timber, and such sterilisation often takes place during the process of injecting preservative liquids into wood. It must be remembered, however, that prolonged exposure of wood to temperatures above the boiling point of water materially weakens the timber. Attention may be directed to the fact that the rela- tively high temperatures prevailing in coal pits tend to promote the disintegration of wood by chemical agents. For instance, zinc chloride, a very efficient and econo- mical wood preservative, can gravely attack timber when used in sufficient concentration at only moderately high temperatures. Iron sulphate, either applied as an antiseptic, or casually occurring in mine water, under- goes decomposition, yielding sulphurous and sulphuric acids, whose destructive action on wood is intensified by rise in temperature. Wood destroying fungi require appropriate raw food material. Some of them can feed upon the sap wood or heart wood of many different kinds of timber; others can attack only hard woods or only soft woods, and sometimes only the sap wood of these; still others may be greater specialists, and capable of attacking only one group (genus) of timbers, say, pine woods. These facts provide a possible means of decreasing decay by selec- tion of an appropriate immune kind of wood to replace decayed timber that has been removed; for instance, if the fungus doing harm locally or generally in a pit attacks soft woods exclusively, these pine pit props can be replaced by a hard wood. Or again, if a pine pit prop be rendered rotten by a fungus that cannot attack larch, it may be replaced by a larch prop, which will then not be infected from the pine capping, which is also probably decaying from the same cause. But before we can apply this economical method of sanitation, it is necessary to have full information as to the habits of the fungi con- cerned, and for this research is necessary. The facts already given serve to expldin why it is that the durability of one and the same wood varies in different pits, and that the relative durability of different woods in different mines will not always be the same. At Commentry, in France, the following w7ere the esti- mates as to durability of pit wood :— Oak .................................. 50 months. Beech ................................ 24 ,, Pine, cherry, rowan, birch, and poplar 18 ,, False acacia ” (Robinia) ............ 9 ,, Hornbeam and sycamore ................. 6 ,, At the same pits the following was the order of dura- bility noted in certain observations, the list beginning with the most and concluding with the least durable : Oak, Scots (“ Baltic ”) pine, alder, ash, cluster pine, “ false acacia,” willow, sycamore, elm, aspen, cherry, birch, hornbeam, beech, and poplar (other than aspen). The different position of beech in the two lists is notice- able. In this country Scots (“Baltic”) pine,. cluster pine (from France), larch, oak, with some small quan- tity of ash and birch, appear to be the woods chiefly used. It is also stated that in some pits Norway spruce is employed. Of these timbers, larch and oak are the most durable at ordinary levels. As to the comparative durability of these woods in pits in this country, I have no statistics available. It is assumed that the different kinds of wood vary in durability in accordance with the amount of fungus repelling or antiseptic material that they contain, or produce when attacked. And this leads to the fact that artificial durability may be given to timbers by the 'application of antiseptics or fungicides. All solutions may act antiseptically if sufficiently con- centrated. For instance, sugar, though a food admir- ably suited to promote the growth of fungi, arrests the growth of these when used in a concentrated form. Common salt (sodium chloride) in concentrated solu- tion is an antiseptic, and when naturally abundant in coal pits undoubtedly protects the wood. But its hygro- scopic qualities and relative weakness of action detract seriously from its value as an artificial antiseptic. Ferrous sulphate is very uneven in its effects, some- times considerably prolonging the life of timber, at other times being associated with rapid decay. Undergoing oxidation, it deposits oxide of iron on and in the wood, and thus tends to check the ingress of water; but it pro- duces sulphurous and sulphuric acids, wdiich may, on the one hand, attack the wood directly, and, on the other hand, successively act as an antiseptic and a food material in relation to fungi. These facts suggest the whitewashing of bare wood in pits where ferrous sulphate is abundant in mine water. The lime present will neutralise the acids, and tend to form an impervious sheet outside the wood. Corrosive sublimate is not to be recommended, being extremely poisonous. It is dangerous to handle; more- over, it is easily washed out, and is volatile. Copper sulphate as a fungicide in wood gives remark- ably variable results. Sometimes it is very efficient, but in other cases it causes very rapid disintegration of the wood (possibly because of the free acid). In the presence of ferrous sulphate its destructive action is especially marked. Hence, copper sulphate cannot be recommended for use, and must be especially avoided when mine water contains ferrous sulphate. Taking into consideration initial cheapness and pro- longed efficiency, zinc chloride is the best inorganic fungicide for use in connection with the preservation of wood. As a superficial wash, its value is diminished greatly where the wood is exposed to rain. In efficiency it is surpassed by several other salts, such as magnesium fluosilicate. Creosote and its derivatives constitute the best pre- servatives of wood, for creosote is a more powerful fungicide than zinc chloride, and is not washed out. Moreover, if the-wood be seasoned, creosote retards the absorption of water, and thus indirectly contributes to the strength of timber in moist places. Among the cheaper derivatives of creosote may be mentioned cresol calcium, which is being tested on railway sleepers. The most efficient derivatives, however, are the dinitro- phenates and cresotes of sodium and potassium, and one or more of these with admixtures of other sub- stances, may become of commercial importance in this connection. But, as is shown by the succeeding table summarising Fayol’s observations, investigation and trial are required to show the relative efficiency of various antiseptics in different coal pits, as in some cases simple treatment, or cheaper or more dilute antiseptics, will be as efficient as more costly antiseptic treatment. It is now possible to consider the effects of the various types of treatment designed to preserve wood. (1) Seasoning and barking of wood have effects whose limited efficiency has already been discussed. It may here be added that Peters (U.S.A.) found that in dry, well ventilated mines seasoning sometimes increased the durability of the wood by 25 per cent. (2) Carbonising or braizing the outside of timber serves to provide an aseptic or antiseptic, and at least temporarily dry surface, which, however, is liable to be subsequently broken. At the Commentry mines this treatment was often ineffective, though sometimes efficacious. (3) Painting the surface of the wood with various antiseptic liquids yields limited and uncertain results, as it is difficult to secure and maintain an absolutely continuous antiseptic coating. Nevertheless, where the antiseptic could not be washed off, and the substance used was creosote, Peters showed that seasoned loblolly pine had an increased durability of from 50 to 100 per cent. So that, where most costly and effective methods are not adopted, this may be recommended. Comparative Durability of Pit Props in Coal Pits at Commentry (compared with Untreated Wood, which is RECKONED AS 1). , v Nature of the wood. Immersed in, or treated with Mine water. Super- ficially braized. ■ Tar. Creosote. Sulphate of copper. Sulphate of iron. Chloride of zinc. Oak, common 10*4 1 14*4 3*6 38*4 28*8 14*4 Cluster pine 1 1 ( 50 I t 2*33 j 40 5*33 2*66 8 Alder 1 ' 1 2*11 40 4 10 ^0 Beech 1 1 37 6 1*75 50 7*5 50 False acacia (Robinia) 1-2 , 7*22 5*33 2*2 . 8 26*6 40 Hornbeam ; 3 ' i 2’5 7 15 . —■ 12 50 Sycamore 2*5 3 6 12 7*5 — —. Cherry rc>6 3’16 — 2*5 1*83 — Aspen , 1 — 2*5 — 2*5 8 — Birch ; 1 ! — — 2*66 13 33 50 Poplar (not aspen) 1 — 2*2 — 11*33 2*61 — Sorbus (rowan, &c.) — ; 1 — — 50 28 Range 10*4-1 7*22-1 (50) 14*4-1 40 1*75 50-2*5 50-1*83 50-8 Average . 2*25 . 2’44 (9*06) 4*73 16*36 13*22 14*85 35*05 Duration of immersion: 12 hours in the cases of the salts of iron, copper, and zinc; 30 minutes in the cases of tar aim ureuwic. The strengths of the solutions were respectively : Iron sulphate, 5 per cent. ; copper sulphate, 10 per cent.; zinc chloride, 10 per cent.; the creosote and tar were heated to 140 degs. Cent. (4) Immersion of the wood in a warm or hot tank of antiseptic is more efficient than the mere painting of the surface with the same preservative, for a more con- tinuous antiseptic coating and deeper penetration are obtained. The accompanying table giving Fayol’s results at Comm entry demonstrates the efficiency of the method in the cases of various timbers and antiseptics. The table must not, however, be taken as an accurate indication of the comparative efficiency of the various antiseptics. Some of Peters’ observations in America seem to illustrate the superiority of tank treatment over mere brush work on the surface; for Peters noted that tank treatment with the relatively weak antiseptic solu- tion, common salt and magnesium chloride (15 per cent.) gave greater durability than brush treatment with the potent fungicide creosote. Where the amounts of timber to be preserved are small, tank treatment is the simplest and most economical method that can be applied. It must be noted, however, that too prolonged treat- ment in a bath at a temperature exceeding the boiling point of water weakens timber, so that pit props are then apt to fail by rupture. (5) Thorough impregnation of the wood by means of pressures exceeding one atmosphere constitutes the method of applying antiseptics that is most efficient, and where large quantities of timber are concerned, most economical. This method is well illustrated by the familiar process of creosoting by pneumatic pressure in closed chambers. Of this normal process there are various modifications, some being designed to ensure thorough penetration of the wood, succeeded by an expul- sion of the excess of creosote. Possibly one of these modifications will be found the most suitable in con- nection with coal pits. So far as decay is concerned, such thorough creosoting confers an increase in dura- bility from perhaps a month or two to an indefinite number of years (creosoted wooden fences still per- fectly sound after 40 years of use, and railway sleepers free from decay after more than 20 years of use in one form or another, are known). In conclusion, it may be pointed out that increased preservation of timber involves not merely a saving from the point of view of the colliery proprietor, but it involves an enormous saving in the amount of timber imported into this country, for most of our pit props come from the Baltic region, and some from France. With the continual rise in the price of soft wood timber, this saving will increase with years. W. F. Sherfesee,* assuming that the average life of an untreated pit prop is three years, and of an antiseptically treated pit prop 13 years, and that 40 per cent, of mine timber could be profitably treated antiseptically, concludes that the annual saving to the United States involved by such treatment would be 51,700,000 cu. ft. of timber. With- out relying too greatly on Sherfesee’s estimates, and still less without applying them to this country, they sufficiently indicate the immensity of the saving that may be possible in this country by improved sanitation and appropriate treatment of wood in mines. * “ Wood Preservation in the United States,” by W. F. Sherfesee, U.S.A. Forest Service Bulletin 78. BRITISH MINING INDUSTRY AND THE WAR. In the course of his presidential address to the Institution- of Mining and Metallurgy, Sir R. A. S. Redmayne, K.C.B., said that he spoke not in his capacity of Chief Inspector of Mines, but as a mining engineer, desirous of ventilating some matters which engineers considered of great moment, and of trying to solve some problems in connection with mining, which now, more than ever, were of national importance. The war would be followed by a period of industrial depression, amounting possibly to something like prostration, but he believed also, that we had it within our power to remedy matters in a comparatively short period, and to put the nation on a stronger, financial and industrial basis than ever before in its history. We must take time by the forelock and make our plans now. The war had emphasised one outstanding fact, viz., that we should and could approximate more closely to ■the ideal state of being self-supporting; in other words, develop to the utmost our natural resources and put them to the most economical use at home. Inventory of Mineral Resources Desirable. Great Britain was the most highly mineralised area in the world. No other country contained such a variety of mineral resources of use to mankind, not- even the United States of America. If we extended our view and took the whole British Empire, there was-no fuel, ore, stone, or clay which was not contained therein. It behoved us .to know exactly .where we stood in respect of our mineral* resources; where; the different kinds of minerals occurred, of what qualify,,and.to what extent. A great deal of information "existed on the subject in the Transactions of various technical institu- tions, in geological memoranda, and • in . reports on mining properties, which, in the hands of a body of mining experts, could be summarised so as to form part of a large work resulting from further enquiry and inves- tigation. Would not the services of the institution be of value in the prosecution of such an idea? Extending Coal Fields and Preventing Waste. Limiting consideration to the mineral resources of the United Kingdom, the most important mineral asset was coal, the next in importance being iron ore. An esti- mate of the available resources of coal was made by the Royal Commission on Coal Supplies which reported in 1905. But since that date our-knowledge in respect of the available resources of coal ' had been considerably enlarged. The extension — then of a somewhat speculative character—of the Notts and. South Yorkshire fields had since been proved, and the limits were now roughly known. The compass of the Kent coal field had been more correctly determined, and extensions of the Warwickshire field had been proved. Geologists were