It is now known that decay in wood is caused by fungi or low forms of plant life which cannot live without a certain amount of water, food, heat and air.
A fence post decays first at the place where it enters the ground, because at that point the conditions are most favourable. If wood can be kept entirely under water, one item—air—is lacking, so the fungous growths cannot exist and the wood will last indefinitely. This has been proved in many instances. One of the old Viking ships was raised from the bottom of the Christiania Fjord, Norway, after having been under water for a thousand years and it was found to be in a perfect state of preservation. Even the rudder oar or steerboard and wooden shields were intact.
As soon as it was brought into the air the process of decay began, and it became necessary to coat it with preservative. It stands today, 103 feet long, in the museum at Christiania.
Many other instances of under-water preservation might be mentioned.
The other extreme is also true. Wood which is kept perfectly dry will last indefinitely, as in the case of woodwork taken from the pyramids of Egypt, 3,000 years old, which is found to be perfectly preserved.
Fig. 233. A pile
Fig. 233. A pile
But when wood is alternately wet and dry it decays rapidly. A pile driven into the bottom of a tidal river is a good illustration. If such a pile be divided into four sections (seeFig. 233),ais always in the ground,bis always in the water,cis alternately in air and water,dis always in the air. Sectionsaandbmay be considered to be under the same conditions and should last the longest;cshould decay first:dwould last indefinitely if the atmosphere were always perfectly dry; but humidity and rain, air and heat combined finally bring about decay, and although this part of the pile will last longer thancit will in time decay. Sectioncshould be coated with a preservative.
Various woods under the same conditions act verydifferently and according to no well understood law. For example, in contact with the soil black locust is our most durable wood. It is very hard, and its life under these conditions is estimated at from ninety to a hundred years. Red cedar comes next, though it is soft wood. Oak decays in a few years; chestnut, much softer, lasts two or three times as long. Our approaching timber famine has induced a study of this subject, since the preservation of wood is becoming an absolute necessity.
It has been found that certain materials put on the wood before it is placed in the ground prolong its life. Coal tar, wood tar, paint, and creosote all help, but creosote has so far proved to be the best. It is one of the by-products of coal tar and is being used extensively by the railroad companies for prolonging the life of ties.
Experiments with creosote have brought out some very interesting facts. It has been found that after being treated with the hot creosote all woods resist decay alike, regardless of their hardness or softness. Consequently, a treated cheap wood will last as long as an originally valuable one. This is a great gain, as it allows us to make use of wood like the poplar which would otherwise be practically of no value.
The various coatings we put on wood, such aspaint, varnish, oil, etc., are intended not only to beautify but to preserve it, which they do by filling up the pores and excluding moisture, preventing fungous growths, etc. All of these coatings should be put only on dry wood, else they prevent evaporation of the sap and may hasten decay.
Fig. 234. Strains
Fig. 234. Strains
Drying lumber increases its strength, as it has been found by experiment, even as much as 400 per cent. if no checking occurs. When this happens it counteracts much of the gain, and if the wood absorbs moisture once more the strength will decrease. The strength of the various timbers varies greatly, and sap wood is usually weaker than heart wood.
The strains that may be brought to bear on timbers are illustrated inFig. 234, the arrows indicating the directions in which the forces operate. Atathe wood is under tension, the forces at work on it tending to pull it apart. Atbthe piece isunder compression, the forces tending to reduce its length by forcing its fibres together. A pillar supporting a weight is under compression. Atcthe weight tends to bend the beam. The upper part is under tension, the lower part under compression. This is known as beam action, and depends on whether the beam is supported at one end, as shown, or on both ends. Also it is important to know whether the beam has a uniformly distributed load or whether the weight is at one point only. The problems relative to beam action are largely of an engineering character and involve considerable mathematics.
Shearing is the sliding of one part of the timber along the grain. If a piece of wood is cut to the form shown atdand a weight applied ate, the tendency will be for this upper part to slide down as shown atf. When this occurs, shearing has taken place.
The strength of wood differs in resisting these various strains, the tensile strength being greater than the crushing or compressive strength. Ash, for example, has a tensile strength of 16,000 pounds to the square inch, but its crushing strength is only 6800 for the same size. The tensile strength of dry white pine is 10,000 pounds, its crushing strength5400 pounds, and its shearing strength varies from 250 pounds to 500 pounds, showing that its weakest point is along the grain. If the young woodworker becomes ambitious enough to think of designing a bridge or large building he can find these figures in any engineers' hand-book. There are so many important factors to be considered that the amateur will do well to go ahead with great caution. Knots and other defects reduce the proportionate strength of large beams greatly, so that it would not be safe to assume that a beam 6 inches square would be 36 times as strong as a piece 1 inch square.
In upright posts of considerable length, not alone the crushing strength must be considered, but a bending action enters into the problem. Wherever the question of danger to life enters, as in a bridge or a house, it is wise to leave a large margin for safety. We realize this fully when we read of a grand stand holding hundreds or thousands of people collapsing under the weight. The architect has also to reckon with still other elements, such as wind pressure and vibration.
The woodworker soon discovers that arithmetic is a very practical and necessary subject. He will meet many problems both in drawing and in actual construction which test his ability and call for some knowledge even of elementary geometry. It is important to be able to estimate from his drawing just how much lumber will be needed. He will soon discover through intercourse with dealers in lumber that there are certain standard sizes, and he should make his designs as far as possible conform at least to standard thicknesses.
Common boards are sawed 1 inch thick. When dressed on two sides the thickness is reduced to7⁄8. In planning some part of a structure to be 1 inch thick it is better to make the dimension7⁄8inch, else it will be necessary to have heavier material planed to 1 inch and the cost will be that of the heavier lumber, plus the expense of planing. In buying1⁄2-inch dressed lumber, very often inchboards are dressed down to the required thickness, and the purchaser pays for 1-inch wood, in addition to the dressing. The boy is surprised to find that it costs more for1⁄2-inch than for inch material. Standard lengths are 10, 12, 14, 16, etc., feet. Widths vary, and as wood shrinks only across the grain—with one or two exceptions—this dimension cannot be depended on, as the amount of shrinkage depends somewhat on the age after cutting. Whenever possible, it is wise to go to the lumber yard and select your own material, choosing boards that are free from knots, shakes, etc. Clear lumber—free from knots—costs more, but is worth the difference.
A measurement is a comparison. We measure the length of a lot by comparing it with the standard of length, the yard or foot. We measure a farm by comparing its area with the standard unit of surface measure, the acre, square rod, or square yard.
In every measurement we must first have an accepted standard unit. The history of units of measurement is a very interesting one, and its difficulty arises from the fact that no two things in nature are the same. One of the ancient unitsof length was the cubit, supposed to be the length of a man's forearm, from the elbow to the end of the middle finger. This, like other natural units, varied and was therefore unreliable. As civilization progressed it became necessary for the various governments to take up the question of units of measurements and to define just what they should be.
Our own standards are copied from those of Great Britain, and although congress is empowered to prescribe what shall be our units, little has been changed, so that with few exceptions we are still using English measurements.
The almost hopeless confusion and unnecessary complication of figures is shown in the following tables as compared with the metric system:
12 inches= 1 foot3 feet= 1 yard(standard)51⁄2yards}}= 1 rod}or161⁄2feet320 rods}}} = 1 mile}}or1760 yardsor5280 feet.001= millimetre.01= centimetre.1= decimetre1.= metre10.= dekametre100.= hectometre1000.= kilometre
The original English definition of an inch was "three barley corns" with rounded ends. The meter is 1/10,000,000 (one ten-millionth) of a quadrant of the earth's circumference,i. e., the distance from the pole to the equator measured along one of the meridians of longitude. The length of three barley corns might be different from the next three, so here was the original difficulty again. The designers of the metric system went back to the earth itself as the only unchangeable thing—and—are we sure there is no change in the earth's circumference? The great advantage of the metric is that it is a decimal system and includes weights as well as surfaces and solids. Our weights are even more distracting than our long measure. We have in fact two kinds of weight measure—troy and avoirdupois.
TROY24 gr.= 1 pwt.20 pwt.= 1 oz.12 oz.= 1 lb.5760 gr.= 1 lb.AVOIRDUPOIS16 oz.= 1 lb.112 lb.= 1 cwt.20 cwt.= 1 ton2240 lb.= 1 long ton2000 lb.= 1 short ton100 lb.= 1 short cwt.7000 gr.= 1 lb.METRIC.001milligram.01centigram.1decigram1.gram10.dekigram100.hectogram1000.kilogram
In surface measurements, the same differences are seen:
AMERICAN OR ENGLISH9sq. ft.= 1 sq. yd.301⁄4sq. yds.= 1 sq. rod160sq. rods}}= 1 acre4840sq. yds.640acres= 1 sq. mileMETRIC.0001sq. centimetre.01sq. decimetre1.sq. metre100.are10,000.hectare1,000,000.sq. kilometre
In measures of volumes we are as badly off:
DRYLIQUID2 pints= 1 quart2 pints= 1 quart8 quarts= 1 peck4 qts.= 1 gallon4 pecks= 1 bushel1 gal.= 231 cu. ins.4 quarts= 268.8 cu. ins.1 heaped bushel=11⁄4struck bushels.The cone in a heaped bushel must be not less than 6 ins. high.METRIC.001millilitre.01centilitre.1decilitre1.litre or cu. decim.100.dekalitre1000.hectolitre
As if this were not enough, when we go to sea we use another system. The depth of water is measured in fathoms (6 feet = 1 fathom), the mile is 6086.07 feet long = 1.152664 land miles, and 3 sea miles = 1 league. In our cubic measure:
1728 cubic inches= 1 cubic foot27 cubic feet= 1 cubic yardA cord of wood is 4 ft. × 4 ft. × 8 ft.= 128 cubic feet.A perch of masonry is 161⁄2× 11⁄2× 1= 24.75 cubic feet
Isn't it about time we used the metric system? The reader will not mind one more standard unit. Lumber is measured by the board foot. Its dimensions are 12 × 12 × 1 inches; it contains 144 cubic inches and is 11⁄12of a cubic foot. A board 10 feet long, 1 foot wide and 1 inch thick contains 10 board feet. One of the same length and width but only1⁄2inch thick contains 5 board feet.
The contents of any piece of timber reduced to cubic inches can be found in board feet by dividing by 144, or from cubic feet by multiplying by 12. As simple examples: How many board feet in a piece of lumber containing 2,880 cubic inches?2880⁄144= 20 board feet. How much wood in a joist 16 feet long, 12 inches wide and 6 inches thick? 16 × 1 ×1⁄2= 8 cubic feet: 8 × 12 = 96 board feet. A simpler method may be used in most cases. How much wood in a beam 9 inches × 6 inches, 14 feet long? Imagine this timber built up of 1-inch boards. As there are nine of them, and each 14 ft. ×1⁄2foot × 1 inch and contains 7 board feet (Fig. 235), 7 × 9 = 63 board feet. Again, how much wood in a timber 8 inches × 4 inches, 18 feet long? This is equivalent to 4 boards 1 inch thick and 8 inches or2⁄3foot wide. Each board is 18 ×2⁄3× 1 = 12 board feet, and 12 × 4 = 48, answer. (Seeb,Fig. 235).
To take a theoretical case: How much wood in a solid circular log of uniform diameter, 16 inches in diameter, 13 feet and 9 inches long? Find the area of a 16-inch circle in square inches, multiply by length in inches and divide by 144.
16 × 16 × .7854 = 20113 ft. 9 in. = 165 inches(201 × 165)⁄144= 13045⁄144board feet
It is not likely that a boy would often need to figure such an example, but if the approximate weight of such a timber were desired, this method could be used, reducing the answer to cubic feet and multiplying by the weight per cubic foot.
A knowledge of square root is often of great value to the woodworker for estimating diagonals or squaring foundations. The latter is usually based on the known relation of an hypothenuse to its base and altitude. It is the carpenters' 3-4-5 rule. The square of the base added to the square of the altitude = square of the hypothenuse. 3² = 9, 4² = 16; 9 + 16 = 25. The square root of 25 is 5. (SeeFig. 235). To square the corner of his foundation the carpenter measures 6 feet one way and 8 the other. If his 10-foot pole just touches the two marks, the corner is square. 6² = 36, 8² = 64; 36 + 64 = 100. √100 = 10. This method was used in laying out thetennis court, the figures being 36, 48, 60—3, 4, and 5 multiplied by 12.
To take a more practical case, suppose we are called upon to estimate exactly, without any allowance for waste, the amount of lumber in a packing case built of one-inch stock, whose outside dimensions are 4 feet 8 inches × 3 feet 2 inches × 2 feet 8 inches. Referring to the drawing (Fig. 235,d), we draw up the following bill of material:
2pieces(top and bottom)4 ft. 8 in. × 3 ft. 2 in.2″(sides)4 ft. 8 in. × 2 ft. 6 in.2″(ends)3 ft. 0 in. × 2 ft. 6 in.
The top and bottom, extending full length and width, are the full dimensions of the box, while the sides, although full length, are not the full height, on account of the thickness of the top and bottom pieces—hence the dimensions, 2 feet 6 inches. From the ends must be deducted two inches from each dimension, for the same reason. In multiplying, simplify as much as possible. There are four pieces 2 feet 6 inches wide; as their combined length is 15 feet 4 inches, we have 151⁄3feet × 21⁄2feet = 381⁄3square feet. The combined length of top and bottom is 9 feet 4 inches = 91⁄3× 31⁄6= 295⁄5, and 381⁄3+ 295⁄5= 678⁄5or 68 board feet, ignoring such a small amount as1⁄5of a foot. This is close figuring,too close for practical work, but it is better to figure the exact amount, and then make allowances for waste, than to depend on loose methods of figuring, such as dropping fractions, to take care of the waste.
Fig. 235. A packing case
Fig. 235. A packing case
As a good example of estimation, take the hexagonal tabourette shown inFig. 178; the five pieces, aside from the hexagon under and supporting the top, which may be made from scrap lumber, are shown laid out inFig. 236. The board must be at least twelve inches wide in order to get out of it the large hexagon. The legs may be laid out as shown with space left between for sawing, yet even by this method considerable waste will result, and it should be kept constantly in mind that as far as possible waste is to be reduced to a minimum. "Wood butcher" is the common shop name forthe workman who spoils more material than he uses.
The great advantage of making out a bill of material before starting is that it not only makes you study your drawing, but causes you to consider the best method of laying out the blank pieces.
Fig. 236. Laying out the pieces for a tabourette
Fig. 236. Laying out the pieces for a tabourette
It is often necessary to find the areas of figures other than the square or parallelogram. Assume that we are to floor a room in an octagonal tower or summer house. If the distance across the flat sides of the octagon is sixteen feet, leaving out the item of waste, how many square feet will be required?
Fig. 237. Finding the area of an octagon
Fig. 237. Finding the area of an octagon
The octagon may be drawn in a square and its area will be that of the square, less the four triangles in the corners. (Fig. 237). So the problem resolves itself into finding the area of one of these triangles. If we knew the length of one of the sides of the octagon, the solution would be simple, but we only know that the eight sides are equal. The following method may be worked out: Find the diagonalof the sixteen foot square. It is 22.6+. Deduct the distance across the flats, 16, leaving 6.6 feet equally divided betweenaandb;a= 3.3 and it may be proved thatc=a=d. So in each corner we have a triangle whose base is 6.6 × 3.3. The area of a triangle equals half its base by the altitude. Therefore the area of each triangle is 3.3 × 3.3 and 3.3 × 3.3 × 4 equals 43.56 square feet, the combined area of the four corners. This deducted from the area of the square leaves the area of the octagon, or 256-43.56 = 212.44 square feet.
Fig. 238. Problem of the hexagon
Fig. 238. Problem of the hexagon
Assume that our problem is to find the narrowest board we can use to cut out a hexagon whose diameter is fourteen inches. As shown in Chapter IV, the hexagon is drawn in a circle. One of the sides is equal to the radius or half the diameter. This gives us the arrangement shown inFig. 238, in which our problem is confined to the right-angled triangle whose base is seven and hypothenuse fourteen. From our knowledge of triangles, we deduct the square of seven (49) from the square of14 (196), leaving 196-49 = 147, which is the square of the altitude. Then √147 = 12.12, which is the narrowest board from which we can obtain a hexagon 14 inches in diameter.
These examples are given to show the close connection between woodwork and arithmetic.
It is hardly possible for a boy to select and purchase wood for his various purposes without some knowledge of the different woods and their peculiar characteristics. No two are exactly alike, and in fact two trees of the same kind growing in different parts of the country under different conditions will produce timber of very different qualities. This is specially noticeable in the tulip or white wood, for example. A tree of this species, growing in a swamp in the South, will yield a very different wood from one grown on high ground in the North.
Again, the same wood is known in different localities by different names, so in order to have a sound knowledge of lumber, it is really necessary to know something about the trees. White wood, just mentioned, is called, in many localities, yellow poplar. As a matter of fact, it is not a poplar, nor is it related to the poplars, being a member of the magnolia family.
The following pages, devoted to this subject, are the cream of many talks between our boys, boiled down to the important facts and arranged in some order. It was a hobby of Ralph's, and Harry became so enthusiastic over it that they frequently laid aside their work and took long walks through the country studying trees.
Harry started a small nursery in the garden and is raising young trees from seeds and cuttings. As he remarked to Ralph one day: "It's astonishing how little people know about trees! Why they are the most interesting things that grow. Just think how many things we get from them besides wood; maple sugar, rubber, turpentine, wood alcohol, tannin for making leather, shellac, Canada balsam, spruce gum, and nuts! All of our nuts except peanuts come from trees—hickory, walnuts, butternuts, beechnuts, chestnuts, pecans, almonds, etc."
Ralph noticed that as Harry's interest in the trees grew he became less wasteful of his wood in the shop. The fact that a tree had to be cut, and in most cases killed, in order to furnish him with lumber, seemed to worry him. One day when he was thoughtfully at work in the shop, he blurted out, "It's a shame that so many trees have to be cut down for lumber!"
"Yes," said Ralph, "it seems so; yet if no lumber was wasted, it would not be so bad. It is estimated that 75 per cent. of the wood cut down is wasted."
"How?" asked the boy.
"Well, in the first place, many lumbermen after cutting the tree down, take just the log or lower part and leave the top to decay. It often happens that they leave the tops and branches as a great mass of litter, which soon becomes as dry as tinder, an invitation to the smallest spark to start a fire, and more woodland is destroyed by fire each year than I care to tell you."
"How much?" asked Harry.
"Every year, between twelve and fifteen million acres, and some years three times as much."
"How much is a million acres?"
"You can get some idea from this: Long Island, N. Y., is a hundred miles long and about twenty across in the widest part. It contains about a million acres. Imagine this covered by solid woods, multiply by fifteen and you would have a good idea of the amount of woodland burned over every year."
"Gracious!" exclaimed the boy. "I should think every tree would have been burned years ago."
"Well, this is a big country," said Ralph. "I figured it out once. The United States is large enough to make six hundred states the size of Connecticut, and have room for twenty-five or thirty more. The state of Texas alone could be cut up into a hundred pieces as large as Connecticut.
"The forest fire is one of our worst enemies. It is far worse than the lumberman, because when he cuts down trees it gives hundreds of young seedlings which are struggling to live in the shade a chance to grow and cover the ground with a new forest; but the fire kills these young seedlings and even burns the seeds that are lying in the leaves waiting to grow. That is one of the worst things to be said against the forest fire."
"Does it kill every tree?"
"Oh, no! Trees like the oak sprout from the old roots, but most evergreen trees are killed outright."
"What happens then?"
"Why, it depends. If the forest is mixed, hard woods and conifers, the hard woods, or some of them, will in time send up sprouts, and where you formerly had a mixed stand, you will in a few years have only hard woods, unless some of the evergreens were not touched. In that case, their seeds will in time replace the old evergreens."
"How long does it take?"
"From forty to a hundred years to have a large forest. Some evergreens, like the spruce, increase in diameter very slowly."
"What happens when the forest that is burned is all evergreens, and they are all killed?" asked the irrepressible boy.
"The process of reforesting in that case is very slow. Trees of little value, like the poplar or birch, appear first, because their seeds are light and are carried a considerable distance by the wind. If fires pass over the same area every few years, the forest will never come back unless seeds are planted. There are large areas in this country thus denuded, and instead of a forest we have a scrubby growth of bushes that are of little value to anybody.
"Huckleberries grow in burned-over land luxuriantly, and in some sections it is suspected that the people who make money by gathering the berries burn the brush purposely.
"The forest cover is valuable for other things besides timber. The snow melts slowly in an evergreen forest, because the rays of the sun cannot penetrate with full strength. This allows the water to sink into the ground slowly, and to come out lower down in the form of springs.
"Where there is no forest the snow melts much more quickly, the water rushes down the hills in streams, carrying with it the top soil, which is of so much value to the farmer, cutting the hillsides into gullies, causing floods in the valleys, and filling up the rivers with silt or mud.
"This spoils the streams, ruins the land, and causes millions of dollars' worth of damage to property. If you doubt it, read the newspaper accounts of floods in the valleys of the Ohio, Missouri, and Mississippi every spring."
"But I should think by this time all the soil would be washed away."
"It will be in time. There are large areas in China where the soil is washed away to the bare rock. The population has been obliged to emigrate because when the soil goes, the population can no longer live."
"Well, what are we going to do about it?" asked Harry in amazement.
"Wait a minute," said Ralph, warming up to his subject. "The Mississippi carries into the Gulf of Mexico every year seven and a half billion cubic feet of soil; enough to cover Long Island two inches deep every year."
"What are we going to do?" repeated the boy.
"We can do one of two things," said Ralph sagely, "We can follow in the footsteps of China and let the land go to ruin; or we can follow the example of Germany, take care of our forests—or what is left of them—and plant new ones. It is one of the greatest questions in this country to-day, and you are going to hear a lot about it before you are twenty-one."
The lumber business ranks fourth in the great industries of the United States. The Department of Forestry at Washington estimates that we are using three times as much wood yearly as the annual growth of the forest.
A grand total of 150,000,000,000 board feet of lumber for all purposes, including firewood, is the estimated amount, a figure the mind can hardly grasp.
The railroads of our country rest on 1,200,000,000 ties. The average life of a tie is about ten years, so that we must replace one tenth, or 120,000,000, each year. As the average forest produces two hundred ties to the acre, this item alone calls for half a million acres of woods every year.
The tie is only one item in the great business of railroading, immense quantities of lumber being required for trestles, platforms, stations, bridges, etc., so that a full million of acres must be cut annually to keep our railroads operating.
Place this item against the fifteen million burned, and the statement may be made that we burn enough each year to supply the railroads for fifteen years. To offset this loss several railroad companies are now planting trees for a future supply, as the many attempts to supplant the wooden tie with a manufactured one have not been very successful.
The six thousand mines of various kinds within our border use up 5,000,000,000 board feet every year, and so on through the list of wood-consuming industries. As our population doubles, the consumption of lumber quadruples. To-day, five hundred feet of wood is used annually for every man, woman, and child, as compared with the sixty feet used in Europe. Already our many industries are beginning to feel the shortage, and prices constantly go up.
Turpentine, which is made from the Southern yellow pine, requires a new "orchard" of 800,000 acres yearly to keep up the demand; and when we realize that one third of the lumber cut is yellow pine, it is little wonder that the price of turpentine and other naval stores keeps moving upward.
Where and when will it stop? We read a great deal about the transformation of water power into electrical energy, but the flow of streams is dependenton forests, and the spring floods are followed by drought. While the Ohio River rises forty feet in the spring, it is possible to walk over the river bed almost dry shod the following summer.
We hear much about irrigation, but irrigation is dependent largely on mountain forests.
So a burning question has arisen in these United States, called conservation, or the husbanding of the great resources that have made our country what it is.
The forest resources are different from those of the mines. There is a definite end to the supply of coal, iron, gold, and silver, but by proper care the forest may be made to yield a continuous crop of lumber.
Forestry does not mean the fencing in of the woods, but the handling of them in such a way that no more is cut than the annual growth. This has been practised in Germany on scientific principles with such success that the production has been increased 300 per cent., and where seventy-five years ago they obtained twenty cubic feet from each acre a year, they now cut sixty, and the forest continues to grow luxuriantly.
What Germany has done we can do, and millions of acres now useless can be made to yield large quantities of wood while continually clothed with growing forests.
The cutting of lumber is usually done when the sap is dormant, preferably in the winter. The logs are gotten to the mill by the cheapest method, which usually consists in floating them down a stream or river; but now that most of the remaining forest is remote, it is quite common to have portable mills transported into the woods where the trees are cut and sawed into planks or the larger sizes of timber and from there loaded on the cars.
The old-fashioned method was more picturesque, and the "drive" started with the breaking up of the ice in the spring. Thousands and hundreds of thousands of logs were guided down stream, pulled off shore when they became stranded, and the jams were broken up until the smooth water below made sorting possible.
As several companies might be driving down the same stream, each log was marked by an axe with the private mark of the one to which it belonged. After many vicissitudes, the drive would reach the sorting boom, where the lumber of the various companies would be separated and made up into rafts.
A boom is a chain of logs fastened together by iron chains, and extending into the river. It mayreach clear across, or one end can be anchored in the stream to allow a passage for boats. In that case the river end has to be anchored up stream to catch the logs.
One of the most serious things encountered on a drive is the log jam. It may be caused in many ways but usually by some obstruction, as a shoal, rocks, a narrowing of the river, etc.
The lumberman has a vocabulary of his own, and he recognizes several kinds of jams, such as wing jams, solid jams, etc.
No matter how caused, it is the business of the lumber jack to break up the jam, and sometimes before it can be done a late freeze will occur and the whole mass become solid ice and logs. It is sometimes necessary to use dynamite to break it up. The breaking up is a dangerous time for the driver, who must sometimes run for his life across the moving mass of logs to the shore.
After they are made into rafts, steamers are used to tow the logs to the various mills. It is slow work, but when the destination is reached, the real process of converting the tree into lumber begins. Often the rafts stay in the water for months before being broken up, and the logs guided to the endless chain which drags them up into the mill.
From this time on the action is very rapid. The modern mill is a mass of rapidly moving machinery, guided and controlled by comparatively few men. Three distinct classes of saws are used—circular, band, and gang saws, and different mills in the same neighborhood use different methods.
Band saws are continuous bands of steel, often 48 feet long, and as wide as 8 inches, which pass over two large wheels like a belt. Gang saws are straight and move up and down rapidly. A number of them are fastened to horizontal pieces, the distance apart being adjustable to the thickness of timber desired.
Before passing through the gang saw, the logs are usually edged,i. e., a slab is cut from two opposite sides. The log is then turned over on one of these flat sides, so that as it passes through the gang saw the planks are all the same width.
The slabs or edgings are passed through other saws and cut to the width and length of a lath, all the waste possible being made into lath or other by-products.
As we use four billions of lath a year, this is an important item.
The process varies with the kind of lumber and its future purpose, but a great deal is wasted in manymills. The refuse is used for fuel, and in some cases burned in stacks built specially for the purpose of getting rid of it. This is one of the forms of waste which will undoubtedly be done away with in the future, and already many lumbermen are at work on the problem. The sawdust is conveyed directly to the furnaces under the boiler and used in the generation of steam.