Popular Science Monthly/Volume 29/September 1886/Woods and their Destructive Fungi II
By P. H. DUDLEY, C. E.
AT the close of my former article I described the conditions which are favorable to the growth of the fungi on woods. In this article I present a few examples under similar conditions, to show what takes place as the result of such growth.
Fig. 10 is a representation of a typical example of decay at and below the ground-line of railway-signal and telegraph poles, sign and Fig. 10. fence posts. In the case illustrated, as in a large number of other cases, the sap-wood forms part of the pole, the bark only being removed. At the ground-line the ever-present spores of some of the fungi have germinated, under the influence of the moisture, warmth, and air, and have sent out their delicate mycelia over the wood, the threads penetrating any season cracks or fissures, thence piercing and growing in the wood-cells; the manner of growth is not only interesting but wonderful, and almost leads one to think, for an instant, that the fungi, like animals, have instincts to protect them in their development. Certainly I do not wish to convey that impression, but rather to assert the fact of their certain growth and the consequent destruction of the wood, when the conditions before mentioned are present.
The figure shows a section from a telegraph-pole of black spruce (Picea nigra); the opening at the ground-line was sufficient for the admission of the necessary air to carry on the development of the mycelia and the fermentations, but not large enough to allow the wind and heat to dry up the moisture and check the decay; nor was the opening made until a long time after the internal decay was well advanced, the breaking away of the tissues of the wood occurring more from the inside than the outside. In unpainted poles especially of this wood so exposed to the sun that an exterior shell may be dried, or in painted poles, the decay does not appear above the ground-line on the exterior until after the breaking away of the interior wood-cells. In chestnut poles, the sap-wood being so much thinner, the cells break away sooner than in the spruce.
From the place of growth at the ground-line the mycelia pierce the upright longitudinal cells more readily than they do those of the medullary system, growing up and down, but faster in the latter direction, from the fact that the moisture is retained below the ground line in greater abundance than above. Accompanying the mycelia is a growth of ferments, either of the Schizomycetes (bacteria) or the Saccharomycetes depending somewhat upon the particular fungi and the wood. These aid in carrying on the destruction by producing fermentations, which extend down the wood-cells preceding the growth of the mycelia. The illustration was prepared from a pole of which, five feet in length of the base was in the ground, and decay had followed down the cells four feet, while above-ground the decay only followed up the cells a few inches; the pole being unpainted allowed the moisture to escape sufficiently to retard the upward growth. It will be seen from Fig. 10 that a few inches below-ground the exterior of the wood is not so quickly affected, and, comparatively speaking remains sound until destroyed from the inside, though retaining the moisture and facilitating the growth of the fungi. This illustrates one of the important principles to be observed in the care and preservation of our timber in structures, for it will be seen that exterior protection to unseasoned timber, or to that which is to be in a damp situation, retains the moisture and hastens internal decay.
In the case of painted posts above the ground the paint prevents the escape of the moisture, the mycelia and fermentations grow farther up the cells and the posts often break off on the inside above the earth, while appearing sound outside, with a cone-shaped fracture.
In Fig. 10 the decay was extending toward the center of the pole very slowly, the fermentation not being communicated with as great rapidity by the medullary cells, which are only one fifth to one third as large as the upright cells.
Fig. 11 shows the tangential section of the tamarack, which is quite similar to that of the black spruce. The three largest bundles of rays contain resin-ducts, while the cell-cavities of the rays can just be seen; also the sections of the lenticular markings on the walls; in Fig. 12, they show in position on the walls parallel to the medullary rays; the latter are the lines partly crossing the cut, and composed of short contiguous cells, which are thick-walled and not easily penetrated by the mycelia or destroyed by fermentations. An example of the slow lateral extension of the decay is found in the white cedar, a transverse section of which was shown in Fig. 2 (see August number). In growing trees of this wood some of the lower limbs often die, and, not breaking off close to the body, the fungi grow before the wound heals and start decay in some of the upright wood-cells. Ties from such trees show decayed spots from one half-inch to an inch in diameter which extend through their entire length of eight feet. When the wounds close up, the decay is checked, and the wood is so durable that the ties are mechanically destroyed in the track before the decay spreads from the spots so as to render them unserviceable.
The manner of decay shown in Fig. 10 is quite similar in principle to that occurring in double bridge-planks; where the under side of the lower plank is exposed to the air, a thin shell from one eighth to one fourth of an inch thick remaining dry, checks the evaporation from below of the absorbed moisture from above, and decay takes place from the fact that the necessary conditions for the fungi to grow are supplied.
A large majority of fence-posts, especially on railways, are from small timbers, with the sap-wood remaining except on the face side; on those of chestnut and oak, Polyporus versicolor, Fr., Fig. 8 (see August number), will often be found fruiting near the ground-line, as seen in the figure, while its mycelium has already partially rotted the post. Many other species of fungi will also be found fruiting, though in a majority of cases the mycelia only will be seen. The bark should always be removed from posts or timber to be used in the ground, otherwise it will furnish means for a growth of mycelia, and the posts or wood will decay much quicker than otherwise would be the case. This is readily seen in the forest; dead trees with the bark on will be found more or less covered with fruiting fungi, the wood decaying with great rapidity, while those with the bark off remain sound for a longer time. A striking object in a forest abounding in birch-trees is to see on their dead trunks, of twenty to thirty feet high, ten to twenty specimens of Polyporus betulinus, Fr. (Fig. 13), from one to four inches in diameter, projecting from small openings in the bark, which clasps around their necks and holds them with firmness; it is a sight once seen never to be forgotten, for their presence shows the decay that has taken place, and conveys an impressive lesson. The bark, like the coat of paint on unseasoned wood, has retained the moisture, the mycelia have grown, and the tree will soon be destroyed and fall to the ground. A study of the decay of trees in the forests teaches many lessons of great importance, and in practice to avoid as much as possible the conditions which there conduce to decay. That the decorticated tree does not quickly decay furnishes a fact of general application in the care and preservation of timber, teaching that wood will be protected by paint only when it is thoroughly seasoned or dry, otherwise the paint will furnish the artificial bark and hasten instead of retarding decay. Readers who are conversant with the decay of freight-cars will understand what must be expected from the use of
so much unseasoned lumber in their construction, and will comprehend the conditions furnished for the growth of fungi by the moisture in-side of the cars retained by the outside paint. These facts must be more generally understood before the car-builder will be supplied with seasoned lumber. There lies before me as I write this a piece of timber from a building erected about eight years ago; to prevent the sills from decay, they were covered on three sides with asphalt, and tarred paper underneath the preparation; the wood was so badly decayed that they were replaced two years since. The wood was cracked longitudinally and transversely, the cracks being filled with the mycelia of the fungi which had destroyed it; upon drying, the wood crumbled to dust—the so-called "dry rot." Planks only two inches thick and eight inches wide were tarred on three sides at the same time, and were rotted under the tar over an inch in depth, while the unprotected side was sound. I did not see these timbers before they were treated, but they reveal their history as plainly as though the words were written upon them; the builder coated un-seasoned wood, and produced the result he wished to avoid.
Fig. 14 is partly in vertical section, to show the pores in which the basidia grow bearing the spores.
On the under side of the various Polyporei here illustrated are the pores, just visible to the eye in some species (see Fig. 6 in August number), from ten to twelve thousand occurring per square inch; others are coarser and not so numerous. Minute as are these pores, their interior is studded with the basidia and spores, a few of which, magnified four hundred diameters, are shown in Fig. 15, where a represents sterile cells and b the basidia, usually having four sterigma, each of them bearing a spore.
Fig. 14 represents a very interesting but destructive type of fungi, and, in one sense of the word, parasitic upon living trees. It is drawn from Polyporus fomentarius (Fr.), "Dingy-hoof Polyporus." Pileus ungulate, sometimes four to five inches broad, sub-triangular, obsoletely zoned, nodulose, brownish-gray, resembling coffee slightly tinged with milk; its peculiar form and color make it easily identified. Closely allied to it are Polyporus nigricans (Fr.), Black-hoof Polyporus; pileus pulvinate; Polyporus igniarius (Fr.), Rusty-hoof Polyporus; pileus at first tuberculoso-globose (immarginate); Polyporus fulvus (Fr.), Tawny-hoof Polyporus.
The first three are found upon beeches, willows, hornbeams, cotton-woods, and plums, and trees of similar characteristics, and grow upon live trees, where they have been injured by the breaking of limbs, or by the checking of other limbs, at the junction with the trunk of the tree. Polyporus fulvus (Fr.) is found upon the firs. The mycelia,
once started, will continue to grow in the heart-wood of the tree, while the sap-wood, with its bark, is still growing. If the wound is not closed by the growing tissue, the decay continues, causing hollows in the trees. These are not uncommon sights to those familiar with forests, and the trees almost seem to be conscious that they must keep their bark intact, or the invisible fungi will start and eventually destroy their stately proportions.
A cut in a growing tree will be healed over in a few years, and in many woods, after twenty-five to thirty years, the scar can hardly be found. This fact will be recognized by those who have traced former land-surveys through the forests; upon rerunning the line, chopping into a supposed line-tree is often required to determine the question, the former wound having healed so perfectly as not to leave a scar.
Fig. 16, one fourth size, represents Polyporus pinicola (Fr.), partly in section to show the pores, also the apparent economy in the use of material in providing a surface for the growth of the spores, a succeeding forming over a preceding growth; on the upper portion the spore-bearing surface was renewed three times, and then new tissue pushed out underneath, and one set of pores formed before it was gathered. This fungus is found upon the firs and spruces, and is very destructive to planks of the latter, destroying those of two inches in thickness, in walks in from two to four years, while in station-platforms close to the ground, they do not last that length of time. One interesting feature in regard to this fungus is the quantity of phosphoric acid which was obtained from it by treating with necessary reagents. Potash and lime were also abundant. The watery extract from this fungus nearly resembles in composition the artificial preparations used for the cultivation of molds, and it undergoes fermentation in a few hours in the laboratory, cells of some of the species of Saccharomycetes growing in great abundance. In wood in process of destruction by this fungus, similar cells have been found.
The fungi so far illustrated are but a few of the species of the highest types which produce the so-called "dry rot" in timber, and the list could be extended, though the final results of all are practically similar, all requiring about the same general conditions for growth in order to destroy the timber. Besides those of the highest type, there are many other fungi, which are very destructive. The lower order of Sphæriacei contains some genera which are parasitic upon the trees, especially the Sphæria; others of its species thrive upon decorticated trees and unseasoned sawed timber, and many are associated with the decay of timber that writers have called "wet rot." The distinction from the improperly called "dry rot" is not clear, as in either kind the presence of moisture, air, and warmth combined is essential.
The mycelia of the Sphæria are not so abundant as those of the higher types, but the filaments are larger, stronger, and able to pierce the medullary cells of the sap-wood, destroying them and making a free entrance for air and moisture. Fig. 17 represents Sphæria pilifera (Fr.), as identified by Professor Charles H. Peck, and is drawn from specimens I have found abundant upon the sap-wood of the yellow pine from the South, as stated in the former paper; another form of it is sometimes found from the same locality, having smooth perithecia; this latter form is common in the white pine in Massachusetts.
The affected wood looks dark and moldy, and, upon close examination, the little beaks, about one eighth of an inch long, can be seen projecting from the wood, and, when it is dressed, will show discoloration; if dried, the further growth of the fungus is arrested, but will be resumed if the wood becomes damp. On examination with the microscope, the resin-ducts of the medullary rays (see Fig. 11) will be found filled with the dark-colored threads, spreading to the upright ducts and the wood-cells. Although the dark threads are abundant, discoloring the wood, they alone do not destroy the canals, but are aided by fermentations.
Fig. 18 shows some of the cultivated ferments I obtained from splitting open a block and touching a sterilized needle to a resin-duct destroyed by Sphæria pilifera (Fr.), and then inoculating a culture-tube of prepared gelatine. It will be recognized as a species of Saccharomycetes, but with more elliptical cells than Saccharomycetes cervisiæ, the yeast-plant. In wood further advanced in decay than the destruction of its resin-ducts, rounder cells have been frequently obtained by direct observation with the microscope.
Some species of the Sphæria played important parts, infinitesimal though they were, in inducing the fermentations which helped decay the Nicholson pavement; for in the partially decomposed white-pine blocks I find generally an abundance of the dark hypha, and, in some, the fragments of perithecia, showing it was a Sphæria that produced the dark filaments, and not a modification of the white mycelia of some of the higher fungi which are often found associated with it, or in other portions of the block. The decayed spots in the white cedar before described are more or less filled with the dark-colored hypha of some species of Sphæria.
Fig. 19, magnified ten diameters, represents Sphæria aqitila (Fr.), "Brown nestling Sphæria," very common on limbs on the ground—the mycelium pierces and discolors the wood-cells. An asci containing the ascospores, magnified fifty diameters, is shown in the left side of the figure.
Sphæria morbosa causes the black knot in plum and cherry trees.
In Fig. 20 are represented a few of the filaments and the dark spheres in the resin-ducts and wood-cells I found in some white-pine lumber from Michigan, used for sheathing freight-cars. The wood was discolored and the medullary rays were mostly destroyed, especially those containing resin-ducts, which were penetrated from the exterior, the hypha spreading to the longitudinal resin-ducts and wood-cells; upon drying, the decay was checked, but will commence again on moisture gaining access to the wood, which is likely to be the case in the cars. Such discolored wood should be rejected for all situations where moisture will again be possible, as it will quickly decay and communicate it to other woods. I recently saw a number of window-frames made up with lumber having on a portion of sap-wood which was discolored; the dampness from the stone window-sill, after a short time, will revive the former growth in the base of the frames, and, the exterior paint retaining the moisture, the growth will be facilitated, and cause decay of the wood.
Many of the ferments I have cultivated from some of the species of wood decayed by different fungi are dissimilar in form and manner of growth; some are confined entirely to a surface-growth of the gelatine, and others germinate in small spheres along the line of inoculation,
those nearest the surface only developing to any size, while those below the air-supply do not increase after a few days. The ferments obtained from decaying hemlock grew and liquefied the gelatine very rapidly from the surface downward; no budding ferments were found but those which grew by fission (bacteria) belonging to the Schizomycetes. An interesting and practical point was, that they grew rapidly in alkaline gelatine, while in that of acid they developed slowly; some cultures in the latter have not grown so much from the 1st of April to July 15th as the same kind of ferments did in alkaline gelatine in ten days after inoculation.
Note.—Figs. 21 and 22 are from "The Methods of Bacteriological Investigation," by Dr. F. Hueppe. New York: D. Appleton & Co., 1886.
The great abundance of germs in the air is well shown in attempting to obtain pure cultures of the ferments, as all the care and some of the methods of the pathogenic bacteriologist must be practiced. The fact of their universal presence is more readily demonstrated by Fig. 22.—Inoculating a Culture Tube. growing them than can be done by the microscope alone, as one germ soon grows to a great colony, and to be seen singly may require staining to be differentiated by the microscope, so that it is likely it would have been overlooked in a specimen directly from the wood. The general dissemination of the spores of the fungi of the highest types by the wind has been mentioned; their invisibility like that of the ferments, however, eludes ordinary observation, and the bountiful supply of each, on every stick of timber, or the smallest piece of wood, is unnoticed.
Fig. 23 shows the spores of Coprinus atramentarius (Fr.), "Inky Coprinus," magnified one hundred diameters, which just enables the engraver to define their form. Many spores are much smaller Inoculating and of different shapes, while the ferments found in the hemlock require enlarging to one thousand diameters to be as distinctly seen; what the latter lack in size is made up in quantity; and this it is which enables them to set up such destructive fermentations.
When decayed timber and ties dry, and crumble to dust, some of the ferments which caused their destruction will be disseminated by the winds,and each one can form a colony; not a stick of timber in the vicinity will escape a supply; drying at ordinary temperatures does not destroy, but only renders them inactive for the time being, and harmless until surrounded by the proper conditions for their germination. When these ferments fall upon unseasoned wood which contains from thirty-five to fifty per cent of its weight of moisture, many of them germinate and set up fermentations, especially in the sap-wood, increasing their number, though their further growth may be eventually checked by seasoning; the wood, however, shows the effect in proportion to the extent of the fermentations. Fig. 23, 100/1. The molds play an important part, and are often associated in the decomposition of the sap or fluids in the sap-wood, extending to those of the heart-wood.
The cellulose which composes the principal part of the cell-walls of the various tissues in the wood is of itself quite indestructible, and requires some inducing cause to start its decomposition through the contained sap or moisture, which the fungi can do when warmth and air, the latter in limited quantity, are present for them to grow.
One important aid in the preservation of timber will be, for those whose duty it is to care for it, to acquire more practical knowledge of the fungi which grow on it, and this is not a difficult task. What is needed is to call the attention of the men to the conditions and to the prevention of the growth of fungi. The literature about it is meager, only foreign text-books having been published which describe the general species. Professor Charles H. Peck, in the reports of the New York State Museum of Natural History, from the twenty-third to the thirty-eighth, inclusive, has described a great many species of fungi, and has made the most important American publications to date. For practical use he has done a valuable work in the collection and mounting, in the State Herbarium, at Albany, of over twenty six hundred species, where one can in a short time learn to identify the ordinary species found upon ties and timber. In the Columbia College Herbarium there is a collection of nearly three thousand species of the general fungi of this vicinity, which is also open for study. The facilities for taking up the practical work are abundant. Every railway company has men of sufficient aptitude to learn to identify species and study their conditions of growth, and form from, the materials which can be found upon every mile of their lines, collections of decayed wood, from which the employés can gain knowledge to be put into daily practice to check much of the unnecessary decay of all their wood-work of ties, bridges, cars, and buildings.
The cheapest operation to protect our woods, and quite sufficient for many purposes, is to season or thoroughly dry the timber, reducing the contained moisture from eight to twelve per cent of the weight of the wood; and when in this condition, with a circulation of air around it, to prevent the collection and absorption of moisture, the wood will last indefinitely, as the fungi can not grow in such surroundings. Every one is more or less familiar with the soundness of timber in the upper parts of buildings, while in lower parts near the foundations it is often decayed on account of moisture.
In many situations, however, where timber must be used, the conditions of growth of the fungi are present, and it will decay; some species can be used which resist the attacks of the fungi for a long period, but the final result is decay unless the wood is treated by some process preventing the growth of the fungi, which must be capable of doing either one of two things: 1. It must keep the fibers dry, preventing the absorption of moisture. 2. If the wood must be in a damp place and kept moist, some antiseptic must be present, sufficient to prevent the growth of any of the various kinds of destructive fungi. Timber entirely submerged does not come under these considerations. To use the first process successfully means more than a thin coat of paint or tar on seasoned wood when exposed to continued moisture. It must be some substance which penetrates the tissues of the wood sufficiently far, in case the exterior surface is broken, to prevent any absorption of moisture. Woods impregnated with the heavy tar or lighter oils are protected more from the fact of prevention of access of dampness to the fibers than by the contained antiseptics, unless in the exception of a great percentage of creosote. In the second method the moisture is permitted to come in contact with the fibers of the wood, and reliance depends upon the antiseptic. In this case, the entire wood should be saturated to give the greatest measure of success, not merely an exterior protection of a half-inch or so in depth, the latter fact, as before explained, being the cause of many of the failures which have taken place. The antiseptic treatment, to succeed, must destroy all the germs which have found lodgment in the timber, and also those which may come from the exterior.
In a general paper I can only indicate the antiseptics which have been fairly successful, though in many cases the failures were due not so much to the antiseptic used as to the faulty manner of application, which can be understood from what has been written.
The four antiseptics which are most used now are chloride of zinc, creosote, corrosive sublimate, and sulphate of copper; sulphate of iron and pyrolignite of iron may be mentioned. The treatment of the wood by bichloride of mercury (corrosive sublimate) was called kyanizing; by chloride of zinc, Burnettizing; by creosote, creosoting or the Bethel process; by sulphate of copper, Boucherie's process. Sulphate of copper has been used for over a century in preserving timber, and when well applied the results have been good. The idea of Boucherie was to force the antiseptic through all the wood-cells, which was correct, and the method successful in proportion to the extent it was accomplished.
The attempts to impregnate wood are made now with nearly all of the antiseptics, in large cylinders capable of sustaining from two hundred to three hundred pounds pressure per square inch, one end of which can be opened and closed for admission and withdrawal of the timber. When the cylinders are filled with the timber they are closed, then steam or heat is applied to vaporize the sap or moisture; after this a partial vacuum is produced and sustained for from six to twelve hours, then the moisture is withdrawn from the cylinders, and the antiseptic is pumped in and raised to a pressure of from one hundred and twenty to one hundred and fifty pounds, which is maintained for from six to twenty-four hours. Porous woods are impregnated quite readily, while the heart-wood of the yellow pine (see Fig. 1) and the white oak (Fig. 3 in August number) are not penetrated so easily, and take longer time. The external pressure may be one hundred and fifty pounds per square inch; yet the hydrostatic pressure in the cavities of the cells, not 1 of an inch in area, is quite small, the impregnation being to a great extent by capillary attraction and absorption through the cell-walls.
It is evident from preceding statements and illustrations that untreated railway-ties in the road-bed are of necessity in about as favorable conditions for the growth of the fungi as could be selected, and consequent decay is not only probable but certain and rapid. Ties of the most durable woods, as a rule, only resist decay for from eight to ten years, while inferior qualities only last from four to seven years.
The consumption of ties by our railway system will closely approximate eighty million the present year for repairs, and, as these require to be cut from special trees from thirty to sixty years old, ten to sixteen inches in diameter, will take many trees which, in as many more years, would yield from six to eight times as much timber. This rapid reduction of the prospective timber-supply is one of the serious phases of the question, and is causing grave apprehension as to the future sources of ties, not only to the railway officials, but to all persons who look to the general welfare of the country. Transportation now is so intimately connected with every business, and its cost so much a part of the price of nearly all articles, and especially of food-supplies, that the increasing cost of ties becomes a subject of national importance. The American Forestry Congress is urging the planting of trees and the better care of existing forests. While the measures it urges may help the supply of timber twenty-five or thirty years hence, they can not meet the exigencies of the case in the mean time. Railway-ties only last from one fourth to one tenth of the time required to grow them, and the forests are now being rapidly cut to furnish the supply. Very few of the railway companies are in a position to grow their ties; but, as consumers of such vast quantities of timber annually, they can take more effective measures to stop the growth of the fungi and check the enormous wastes of timber now taking place.
One important step, when storing ties and timber before using, would be to put down blocks or timbers for each end of the piles to rest upon, leaving an air-space underneath, and pile the ties an inch apart. This would permit a circulation of air and prevent the growth of mycelia, which is so frequent on the first, second, and third layers, when placed directly upon the ground. When this is not done, the fungi grow as much in the ties, in two or three months in the summer, as they would in one or two years in the road-bed.
There is one phase of decay in ties which has been generally overlooked; in fact, it would not be noticed except by making special examinations. A slight fermentation, which would only soften or make the fiber brittle under a rail or around a spike, becomes of greater importance in ties than in beams which have a large factor of safety. Ties of many species of wood, when sound, will cut under the rails to some extent, and the rate will be much increased, in case the fibers are softened or weakened by fermentations; this I found to be the fact in several hundred chestnut, oak, and yellow-pine ties which had been removed from the track, on account of abrasion under the rails, and of mechanical injury by repeated spiking. Either side of the rails the ties were sound, and would not be called decayed. In the yellow pine the spikes check and separate the. annular rings, which permits the entrance and growth of the mycelium of its special fungus, and this weakens the fiber and loosens the spike. In white oak and chestnut the layers separate by breaking through the small tracheids surrounding the ducts (see Fig. 3, August number), those of the chestnut more rapidly. The fermentations are retarded in these woods by the tannin in the cells, but they take place eventually, softening and injuring the fibers around the spikes and under the rails.
In ties which are well treated, so as to preserve them, the fermentations are held in check, and the softening of the fibers is prevented, and their durability and consequent wearing capacity are increased. This is an advantage so important that its full benefits can not be appreciated until actual comparisons are made between treated and untreated ties under similar conditions of service. I have parts of treated ties of over thirty years' service under heavy traffic, trebling their ordinary life, while there are numerous instances in which the oak has doubled its life, and the hemlock has given from five to six times its usual service.
The durability of well-treated ties is well established in this country by considerable experience on various railways. In England, France, and Germany the experience is ample, the ties lasting there longer than we can expect them to last here, from the fact that chairs are generally used to hold the rail and distribute the weight to a greater area of wood than is the case with the base of our rails; and, besides, the tonnage per car-wheel is less than ours. It is our freight-cars, with limited spring action, which cause a large portion of the abrasion of the ties. The economy would be great that would result to the railways by prolonging the life of their ties by treatment; this fact was realized long since, but in putting it into practice the information and experience were not sufficient to enable their engineers to secure the anticipated beneficial results. In fact, much of the treatment hastened the decay of the ties and timber, or, when overdone, destroyed their strength. This need be the case no longer, for the study of many of these failures has given much of the information needed, and the experience in treating wood is now extensive. The cheaper grades, such as the beeches, maples, birches, elms, and hemlocks, having a structure sufficient to sustain a heavy traffic, can be treated and substituted at less expense than the first cost of untreated white oak or yellow pine, and have a greater durability. This would effect an immediate-economy in the renewal of ties.
It would be decided economy to treat the higher-priced ties, so as to double their durability. A general example is given of a mile of track on a trunk line, where 2,800 ties are used per mile: This year the ties cost fifty-five cents apiece; to lay them in the track costs fifteen cents more, and their average life will be seven years. To treat these ties would add twenty cents to the above cost, and give them an average durability of fourteen years.
Twenty-eight hundred ties at seventy cents = $1,960, which would be the cost for seven years, and, for fourteen years, twice this $3,920. Twenty-eight hundred ties at ninety cents = $2,520, and these would last fourteen years.
The difference in first cost is $560, and the simple interest on this at five per cent for fourteen years is $392, and this added to the $2,520 makes $2,912, a difference of $1,008 for the treated ties per mile for fourteen years. Local conditions would vary the results, but not the principle.
In the present extensive use of timber and lumber, only the roughest approximate estimate is possible of the annual loss by fungi; and the amount of loss can be indicated in only a few items. The cost of replacing decayed ties by the railways of the United States for 1885 exceeded $30,000,000. Repairs of station-buildings and road-crossings, $19,500,000. Repairs of wooden and wood parts of bridges, $6,250,000 (estimated). Repairs of freight-cars, $22,500,000 (estimated). Repairs of passenger-cars, $7,500,000 (estimated). The renewal of telegraph poles and fixtures on 160,000 miles of line constitutes a large item. The loss to the agricultural interests is much greater. The tenth census reports the cost of fencing in 1879 at $77,763,473, the most of which was for repairs. The loss caused by fungi on the 9,000,000 dwellings, with their accompanying buildings, and the $406,520,055 worth of agricultural implements which appear in the census reports, and that on the 6,654,997 tons of marine, and on wharves above water, form other large items. The lumber interests are also a great loser through the quantities of timber that are destroyed in store. The mere mention of these facts makes it evident that the regular annual loss from this source must be rated at many million dollars.