The Evolution of the Modern Mill.1

The Evolution of the Modern Mill.¹

By C. J. H. Woodbury, Boston, Mass.

The great factories of the textile industries in this country are fashioned after methods peculiarly adapted to the purposes for which they are designed, particularly as regards the most convenient placing of machinery, the distribution of power, the relation of the several processes to each other in the natural sequence of manufacture, and the arrangement of windows securing the most favorable lighting. The floors and roofs embody the most economical distribution of material, and the walls furnish examples of well known forms of masonry originating with this class of buildings.

These features of construction have not been produced by a stroke of genius on the part of any one man. There has been no Michael Angelo, no Sir Christopher Wren, whose epitaph bids the reader to look around for a monument; but the whole has been a matter of slow, steady growth, advancing by hair's breadth; and, as the result of continual efforts to adapt means to ends, an inorganic evolution has been effected, resulting in the survival of the fittest, and literally pushing the weaker to the wall.

This advance in methods has, like all inventions, resulted in the impairment of invested capital. There are hundreds of mill buildings, the wonder of their day, now used for storage because they cannot be employed to sufficient advantage in manufacturing purposes to compete with the facilities furnished by mills of later design. Thus their owners have been compelled to erect new buildings, and, as far as the original purpose of manufacturing is concerned, to abandon their old mills.

In the case of a certain cotton mill built about thirty years ago, and used for the manufacture of colored goods of fancy weave, the owners added to the plant by constructing a one story mill, which proved to be peculiarly adapted to this kind of manufacture, by reason of added stability, better light, and increased facilities for transferring the stock in process of manufacture; and they soon learned not only that the old mill could not compete with the new one, but that they could not afford to run it at any price; the annual saving in the cost of gas, as measured by the identical meter used to measure the supply to the old mill, being six per cent. on the cost of the new mill.

In another instance, one of two cordage mills burned, and a new mill of one story construction was erected in its place. The advantage of manufacture therein was so great that the owners of the property changed the remaining old mill into a storehouse; and now, as they wish to increase their business, it is to be torn down as a cumberer of the ground, to make room for a building of similar construction to the new mill.

It is true that such instances pertain more particularly to industries and lines of manufacture where competition is close and conditions are exacting. Still they apply in a greater or less degree to nearly every industrial process in which a considerable portion of the expense of manufacture consists in the application of organized labor to machines of a high degree of perfection.

These changes have been solely due to the differences in the conditions imposed by improvement in the methods of manufacture. The early mills of this country were driven by water power, and situated where that could be developed in the easiest manner. They were therefore placed in the narrow valleys of rapid watercourses. The method of applying water power in that day being strictly limited to placing the overshot or breast wheel in the race leading from the canal to the river, the mill was necessarily placed on a narrow strip of land between these two bodies of water, with the race-way running under the mill.

To meet these conditions of location, which was limited to this strip of land, the mill must be narrow and short, and the requisite floor area must be obtained by adding to the number of stories. It was essential that the roof of such a mill should be strong and well braced in order to sustain the excessive stress brought to bear upon it. The old factory roof was a curious structure, with eaves springing out of the edge of hollow cornices, the roof rising sharply until about six feet above the attic floor, with an upright course of about three feet, filled with sashes reaching to a second roof, which, at a more moderate pitch than the first slope, trended to the ridge.

The attic was reduced to an approximately square room, by placing sheathing between the columns underneath the sashes, and ceiling underneath the collar beams above; thus forming a cock-loft above and concealed spaces at the sides which diminished the practically available floor space in the attic. This cock-loft and these concealed spaces became receptacles for rubbish and harbors for vermin, both of which were frequent causes of fire.

The floors of such a mill were similar in their arrangement to those of a dwelling. Joists connecting the beams supported the floor; and the under side was covered over by sheathing or lath and plaster, thus forming, as in the case of the roof, hollow spaces which were a source of danger. This method caused at the same time an extravagant distribution of material, by the prodigal use of lumber and the unnecessary thickness of such floors, and entailed an excessive amount of masonry in the walls.

Mills built after this manner were frequently in odd dimensions; and the machinery was necessarily placed in diversified arrangement, calling forth a similar degree of wasted skill as that used in making a Chinese puzzle conform to its given boundaries. Their area depended upon the topography of the site, and their height upon the owner's pocket book. There was in Massachusetts a mill with ten floors, built on land worth at that time ten cents or less per square foot, which has been torn down and a new mill rebuilt in its place, because, since the advent of modern mills, it has failed every owner by reason of the excessive expenditure necessary for the distribution of power, for supervision, and for the transfer of stock in process, in comparison with the mills of their competitors, built with greater ground area and less number of stories.

With the advent of the steam engine as prime mover in mills, and the introduction of the turbine wheel with its trunk, affording greater facilities in the application of water power, the character of these buildings changed very materially, though still retaining many of their old features. One of the first of these changes may be noticed in the consideration which millwrights gave to the problem of fixing upon the dimensions of a mill so as to arrange the machinery in the most convenient manner. Although the floors were still hollow, there was a better distribution of material, the joists being deeper, of longer span, and resting upon the beams, thus avoiding the pernicious method of wasting lumber, and guarding against fracture by tenoning joists into the upper side of beams.

But this secondary type of mills was not honest in the matter of design. The influence of architects who attempted effects not accordant with or subservient to the practical use of the property is apparent in such mills. The most frequent of these wooden efforts at classic architecture was the common practice of representing a diminutive Grecian temple surrounding a factory bell perched in mid air. There were also windows with Romanesque arches copied from churches, and Mansard roofs, exiled from their true function of decorating the home, covering a factory without an answering line anywhere on its flat walls.

I do not mean to criticise any of these elements of design in their proper place and environment; but utility is the fundamental element in design, and should be especially noticeable in a building constructed for industrial purposes, and used solely as a source of commercial profit in such applications. Its lines therefore fulfill their true function in design in such measure as they suggest stability and convenience; and this can be obtained in such structures without the adoption of bad proportions offensive to the taste. In fact, certain decorative effects have been made with good results; but these have been wholly subordinate to the fundamental idea of utility.

The endurance with which brick will withstand frost and fires, and the disintegrating forces of nature, in addition to its resistance to crushing and the facility of construction, constitute very important reasons for its value for building purposes. But the use of this has been too often limited to plain brick in plain walls, whose monotony portrayed no artistic effect beyond that furnished by a few geometrical designs of the most primitive form of ornament, and falling far short of what the practice of recent years has shown to be possible with this material.

Additions of cast iron serve as ornaments only in the phraseology of trade catalogues; and the mixture of stone with brick shows results in flaring contrasts, producing harsh dissonance in the effect. The facades of such buildings show that this is brick, this is stone, or this is cast iron; but they always fail to impress the beholder with the idea of harmonious design. The use of finer varieties of clay in terra cotta figures laid among the brickwork furnishes a field of architectural design hardly appreciated. The heavy mass of brick, divided by regular lines of demarkation, serves as the groundwork of such ornamentation, while the suitable introduction in the proper places of the same material in terra cotta imparts the most appropriate elements of beauty in design; for clay in both forms shows alike its capacity for utility and decoration. The absorption of light by both forms of this material abates reflection, and renders its proportions more clearly visible than any other substance used in building construction.

The modern mill has been evolved out of the various exacting conditions developed in the effort to reduce the cost of production to the lowest terms. These conditions comprise in a great measure questions of stability, repairs, insurance, distribution of power, and arrangement of machinery.

In presenting to your attention some of the salient features of modern mill construction, I do not assume to offer a general treatise upon the subject; but propose to confine myself to a consideration of some topics which may not have been brought to your notice, as they are still largely matters of personal experience which have not yet found their way into the books on the subject. Much of this, especially the drawings thrown on the screen, is obtained from the experience of the manufacturers' mutual insurance companies, with which I am connected. By way of explanation, I will say that these companies confine their work to writing upon industrial property; and there is not a mechanical process, or method of building, or use of raw material, which does not have its relation to the question of hazard by fire, by reason of the elements of relative danger which it embodies.

It is indeed fortunate that it has been found by experience that those methods of building which are most desirable for the underwriter are also equally advantageous for the manufacturer. There is no pretense made at demands to compass the erection of fireproof buildings. In fact, as I have once remarked, a fireproof mill is commercially impossible, whatever effort may be made to overcome the constructive difficulties in the way of erecting and operating a mill which shall be all that the name implies. The present practice is to build a mill of slow burning construction.

FOUNDATIONS.

In considering the elements of such buildings, I wish to devote a few words to the question of foundations, because in the excessive loads imposed by this class of buildings, and in the frequent necessity of constructing them upon sites where alluvial drift or quicksands form compressible foundations, there is afforded an opportunity for the widest range of engineering skill in dealing with the problem. In such instances, a settling of the building must be foreseen and provided for, in order that it may be uniform under the whole structure. This is generally accomplished by means of independent foundations under the various points of pressure, arranged so as to give a uniform intensity of pressure upon all parts of the foundation. It is considered important to limit the load upon such foundations to two tons a square foot, although loads frequently exceed this amount.

There is a large building in New York City which has recently been reconstructed, and the foundations rearranged, where the load reached to the enormous amount of six to ten tons per square foot. It was a frequent occurrence in the class of high mills spoken of to impose loads of so much greater intensity upon the wall foundation than upon the piers under the columns of the mill, that the floors became much lower at the walls than at the middle.

The stone for such foundations should be laid in cement rather than in mortar, not merely because cement offers so much greater resistance to crushing, but because its setting is due to chemical changes occurring simultaneously throughout the mass. The hardening of mortar, on the other hand, is due to the drying out of the water mechanically contained with it, and its final setting is caused by the action of the carbonic acid gas in the air.

Although quicksands are never to be desired, yet they will sustain heavy loads if suitably confined. When inclined rock strata are met with, all horizontal components of stress should be removed by cutting steps so that the foundation stones shall lie upon horizontal beds.

Foundations are frequently impaired by the slow, insidious action of springs or of water percolating from the canal which supplies the water power for the mill; and the proper diversion of such streams should be carefully provided for.

In the question of foundations, there is much of a general nature which is applicable to all structures; but, at the same time, each case requires independent consideration of the circumstances involved.

WALLS.

In addition to what has been said, there is but little for me to offer on the subject of walls beyond the general question of stability. In mill construction, walls of uniform thickness have been displaced by pilastered walls, about sixteen inches thick at the upper story, and increasing four inches in thickness with each story below.

The remainder of the walls is from four to six inches less in thickness than at the pilasters. Frequently the outside dimensions of these pilasters are somewhat increased, giving greater stability and artistic effect. By leaving hollow flues within them, and using these flues as conductors for heated air which may be forced in by a blower, such pilasters afford a means for the most efficient method of warming the building.

Consideration must be given to the contraction of brick masonry, especially when an extension or addition is to be made to an older building. This shrinkage amounts to about three-sixteenths of an inch to the rod, an item which is of considerable importance in the floors of high buildings, where the aggregate difference is very appreciable. Some degree of annoyance is caused by neglect to consider this element of shrinkage in reference to the window and door frames, which should have a slight space above them allowing for such contraction. This contraction is often the source of serious trouble in brick buildings with stone faces, the shrinkage of the brick imposing excessive stress on the stone. Instances of this are quite frequent, especially in large public buildings, notably the capitol at Hartford and the public building at Philadelphia, where the shivering of the joints of the stone work gave undue alarm, on the general assumption that it indicated a dangerous structural weakness. The difficulty has, I believe, been entirely remedied in both cases.

The limit of good practice on loads upon brickwork is eight to ten tons per square foot, although it is true that these loads are largely exceeded at times. It is not to be shown, however, that the limits of safety in regard to desirable construction should be confined to the use of masonry for any low buildings. Structures which may be said to be equal to those of brickwork, as far as commercial risk is concerned, can be built wholly or in part of wood so as to conform to all practical conditions of safety. This statement does not apply except to low buildings of one or possibly two stories in height, where the timber cannot be subjected to the intense blast of flame occurring when a high building is on fire.

Mr. George H. Corliss, the eminent engine builder, of Providence, first built a one-story machine shop, with brick walls extending only to the base of the windows, above this the windows being very close together, with solid timber construction between them.

Another method is to place upright posts reaching from the sill to the roof timbers, and to lay three-inch plank on the outside of such posts up to the line of the windows. A sheathing on the outside plank between the timbers is laid vertically and fastened to horizontal furring strips. In some instances a small amount of mortar is placed over each of the furring strips. The reason for this arrangement is to prevent the formation of vertical flues, which are such a potent factor in the extension of fires.

WINDOWS.

Light is often limited or misapplied on account of faulty position or size of windows. The use of pilastered walls permits the introduction of larger windows, which are in most instances virtually double windows, the two pairs of sashes being set in one frame separated by a mullion. A more recent arrangement, widely adopted in English practice, is to place a swinging sash at the top of the window, which can be opened, when necessary, to assist in the ventilation, while the main sashes of the window are permanently fixed.

Rough plate glass is used in such windows, because it gives a softer and more diffused light, which is preferred to that from ordinary clear glass. White glass may be rendered translucent by a coat of white zinc and turpentine.

The top of a window should be as near the ceiling as practicable, because light entering the upper portion of a room illuminates it more evenly, and with less sharply marked shadows, than where the windows are lower down.

The walls below the windows should be sloped, in order that there may be no opportunity to use them as a resting place for material which should be placed elsewhere.

FIRE WALLS.

Brick division walls should be built so as to constitute a fire wall wherever it is practicable to do so. Such walls should project at least three feet above the roof, and should be capped by stone, terra cotta, or sheet metal. They must form a complete cut-off of all combustible material, especially at the cornices.

FIRE DOORS.

All openings in such walls must be provided with such fireproof doors as will prove reliable in time of need. Experience with iron doors of various forms of construction show that they have been utterly unreliable in resisting the heat of even a small fire. They will warp and buckle so as to open the passageway and allow the fire to pass through the doorway into the next room.

A door made of wood, completely enveloped by sheets of tinned iron, and strongly fastened to the wall, has proved to resist fire better than any door which can be applied to general use. I have seen such doors in division walls where they had successfully resisted the flame which destroyed four stories of a building filled with combustible material, without imposing any injury upon the door except the removal of the tin on the sheet iron; and the doors were kept in further service without any repairs other than a coat of paint.

The reason for this resistance to fire is that the wood, being a poor conductor of heat, will not warp and buckle under heat, and cannot burn for lack of air to support combustion. A removal of the sheet metal on such a door after a fire in a mill shows that the surface of the wood is carbonized, not burned, reduced to charcoal, but not to ashes.

Many fire doors are constructed and hung in such a manner that it is doubtful whether they could withstand a fire serious enough to require their services.

The door should be made of two thicknesses of matched pine boards of well dried stock, and thoroughly fastened with clinched nails. It should be covered with heavy tin, secured by hanging strips, and the sheets lock-jointed to each other, with the edge sheets wrapping around, so that no seam will be left on the edge.

Sliding doors are preferable to swinging doors for many reasons, especially because they cannot be interfered with by objects on the floor. But, if swinging doors are used, care should be taken that the hinges and latches are very strong, and securely fastened directly to the walls, and not to furring or anything in turn attached to the walls. The portion of the fixtures attached to the doors must be fastened by carriage bolts, and not by wood screws.

Sliding on trucks is the preferable method of hanging sliding doors, inclined two and one half inches to the foot, and bolted to the wall. The trucks should be heavy "barn door hangers," bolted to the door; and a grooved door jamb, of wood, covered with tin similar to the door, should receive it when shut. A step of wood will hold the door against the wall when closed. A threshold in the doorway retards fire from passing under the door, and also prevents the flow of water from one room to another.

These doors are usually placed in pairs, and sometimes an automatic sprinkler is placed between them.

Fire doors should always be closed at night. In some well ordered establishments there is a printed notice over each door directing the night watchmen to close such doors after them. In a storage warehouse in Boston, the fire doors are connected with the watchman's electric clock system, so that all openings of fire doors are matters of record on the dial sheet.

Fire doors should certainly be closed at times of fire; yet, that such doors are open at night fires, or left open by fleeing help at day fires, is an old story with underwriters. A simple automatic device can be used to shut such doors. It consists of two round pieces of wood with a scarfed joint held by a ferrule, forming a strut which is placed on two pins, keeping the door open, as other sticks have long since served like purposes.

The peculiarity of this arrangement is that the ferrule is not homogeneous, but is made up of four segments of brass soldered together with the alloy fusible at 163 degrees Fahr., which is widely known for its use in automatic sprinklers. When the solder yields, the rod cripples, and the door rolls down the inclined rail and shuts. At any time the door can be closed by removing one end of the rod from one of the pins and allowing it to hang from the other pin.

MILL TOWERS.

Because of economic reasons for preserving the space within the walls of the mill so that it may be to the greatest extent available for the best arrangement of machinery, the stairways should be placed outside of the building. Such stairways should not be spiral stairways, but should be made in short straight runs with square landings, because in the spiral stairway the portion of the stairs near the center is of so much steeper pitch that it renders them dangerous when the help are crowding out of the mill.

The wear of stairs from the tread of many feet presents a difficult problem. A very common practice consists in covering each tread with a thin piece of cast iron marked with diagonal scores, and generally showing the name of the mill. These treads wear out in the course of time, but for this use they answer very well, although somewhat slippery.

A wood tread gives a more secure foothold upon the stairway; and in some instances stairs have been protected by covering the treads with boards of hard wood, containing grooves about three-eighths of an inch deep, and of similar width, with a space of half an inch between them. These boards are grooved on both sides and placed on the stairs. After the front edge is worn, they are turned around so as to present the other edge to the front, and, in course of time, turned from the exposed side to do service in two positions on the other side. In this manner these tread covers are exposed to wear in four different positions.

Mill towers, besides containing the stairways, also serve other purposes, as for cloak rooms for the help. They often contain a part of the fire protective apparatus, carrying standpipes with hydrants at each floor. For this use they are easily available, and furnish a line of retreat in case a fire spreads to an extent beyond the ability of the apparatus to cope with it. These towers also furnish an excellent foundation for the elevated tank necessary for the supply of water for the fire apparatus in places unprovided with an elevated reservoir.

In view of the terrible and deplorable accidents which have occurred by reason of lack of proper stairway facilities at panics caused in time of fire, I would repeat the words of the late Amos D. Lockwood, the most eminent mill engineer which this country has yet produced, when he said to the New England Cotton Manufacturers' Association, "You have no moral right to build a mill employing a large number of help, with only one tower containing the stairways for exit."

The statute laws of several of the States require fire escapes; but it is a matter of fact that they are rarely used, because people are not often cool enough to avail themselves of that opportunity of escape. I know of one instance where a number of girls jumped out of a fourth story window, because they did not think of the stairways, and did not dare to use the fire escape. In that instance, none of the group referred to tried to go down the stairs, which did furnish a perfectly safe means of exit to a number of others.

Most of the fire escapes are put up so as to conform to the letter of the law; and in such manner that no one but a sailor or an acrobat would be likely to trust himself to them. In crowded city buildings, and in other places where the ordinary means of escape are not in duplicate, it is essential that fire escapes should be provided; but it is a great deal better to make a mill building so that they shall not be necessary as a matter of fact, even if they are put up to conform to the requirements of statute law.

REAR TOWERS.

In addition to stairways, towers are placed at the rear of the mill, for the purpose of accommodating the elevators and sanitary arrangements. It is not desirable that elevators should be boxed or surrounded with anything that would result in the construction of a flue; but it is preferable that they pass directly through the floors, with the openings protected by automatic hatchways which close whenever the elevator car is absent. In the washroom, etc., in these towers, it is desirable to protect the wood floors by means of a thin layer of asphalt.

BASEMENT FLOORS.

There are difficulties connected with the floors on or near the ground, by reason of the dry rot incident to such places. Dry rot consists in the development of fungus growth from spores existing in the wood, and waiting only the proper conditions for their germination. The best condition for this germination is the exposure to a slight degree of warmth and dampness. There have been many methods of applying antiseptic processes for the preservation of wood; but, irrespective of their varying degrees of merit, they have not come into general use on account of their cost, odor, and solubility in water.

It is necessary that wood should be freely exposed to circulation of air, in order to preserve it under the ordinary conditions met with in buildings. Whenever wood is sealed up in any way by paint or varnish, unless absolutely seasoned, and in a condition not found in heavy merchantable timber, dry rot is almost sure to ensue. Whitewash is better.

There has recently been an instance of a very large building in New York proving unsafe by reason of the dry rot generated in timbers which have been completely sealed up by application of plaster of Paris outside of the wire lath and plaster originally adopted as a protection against fire. Wire lath and plaster is one of the best methods of protecting timber against fire; and, if the outside is not sealed by a plaster of stucco or some other impermeable substance, the mortar will afford sufficient facilities for ventilation to prevent the deposition of moisture, which will in turn generate dry rot.

Where beams pass into walls, ventilation should be assured by placing a board each side of the beam while the walls are being built up, and afterward withdrawing it. In the form of hollow walls referred to, it is a common practice to run the end of the beam into the flue thus formed, in order to secure ventilation.

I am well acquainted with a large mill property, one building of which was erected a short time before the failure of the corporation, which resulted in the whole plant remaining idle several years. After the lapse of about five years this establishment was again put into operation; but before the new mill could be safely filled with machinery, it was necessary to remove all the beams which entered walls and to substitute for them new ones, because the ends were so thoroughly rotted that it would have been dangerous to impose any further loads upon the floors. When floors are within a few feet of the ground, unless the site be remarkably dry, it is essential to provide for a circulation of air, which can be done very feasibly in a textile mill by laying drain pipe through the upper part of the underpinning, forming a number of holes leading into this space, and then making a flue from this space to the picker room or any other place requiring a large amount of air. The fans of the picker room, drawing their supply from underneath the building, produce a circulation of air which keeps the timber in good condition.

It is supposed by some that there is a difference in the quality of timber according to the season in which it is felled, preference being given to winter timber, on account of the greater amount of potash and phosphoric acid which it is said to contain at that time. In some parts of Europe it is a custom to specify that the lumber should have been made from rafted timber, on account of the action of the water in killing certain species of germs. Whatever may be the merits of either of these two theories, the commercial lumber of the northern part of this country is generally felled in winter and afterward rafted.

The action of lime in the preservation of wood has always been attended with the most excellent results; although not suited to places subject to the action of water, which dissolves the lime, leaving the timber practically in its original condition. The preservative action of lime upon wood is readily shown by the admirable condition in which laths are always found. I doubt if any one ever found a decayed lath in connection with plaster.

As an example of the action of lime as a preservative of lumber. I can cite an instance of a mill in New Hampshire where the basement floor was placed in 1856, the ledge in the cellar having been blasted out for the purpose. The rock was very seamy, and abounded in water issuing from springs or percolating from the canal supplying water to the mill. The rock was blasted away to a grade two feet below the floor, and most of the space filled up again by replacing the small pieces of stone, so arranged as to form blind drains for the removal of any water which might find its way under the floor.

Toward the top of this filling, finer stones were used, then about three inches of gravel, which was covered with two inches of sand and lime. Two years ago I was at this mill when some alterations requiring the removal of the floor were in progress, and found that the lumber was still in good, sound condition, except for a superficial decay on the under side of the floor plank.

But there are frequent instances where it is necessary to place the floor directly upon the earth, without any space or loose filling underneath it, in order to save room, or to secure a firm support for machinery. By way of information upon what has actually been accomplished in this direction, I will cite instances of three floors in such positions, all of which have to my knowledge fulfilled the purpose for which they were designed.

The first instance is that of a basement floor laid twenty-one years ago, a portion of which was made by excavating one foot below the floor, six inches of coarse stone being filled in, then five inches of coal tar concrete made up with coarse gravel, and finally about one inch of fine gravel concrete. Before the concrete was laid, heavy stakes were driven through the floor about three feet apart, to which the floor timbers were nailed and leveled up. The concrete was then filled in upon the floor timbers, and thoroughly tamped and rolled out to the level of the top of the floor timbers. The under side of the floor timbers was covered with hot coal tar.

This floor is still in good condition, and has not needed repairs caused by the decay of the timber. Another portion of the floor laid at the same time and in the same manner, with the exception that cement concrete was used in the place of the coal tar, was entirely rotted out in ten years.

Another floor was made in quite a similar manner. All soil and loam was removed from the interior of the building; the whole surface was brought up to the grade with a puddle of gravel and ashes; stakes two and a half by four inches, and thirty inches in length, were driven down; and nailing strips were secured to them. Over this puddled surface a coat of concrete eight inches thick was laid, the top being flush with the upper surface of the nailing strips. This concrete was made of pebbles about two inches in diameter, well coated with coal tar, and laid in place when hot. It was then packed together by being tamped and rolled, and a thin covering of the tarred sand placed upon the top, forming a smooth, hard surface. The first floor consisted of two inches of matched spruce, grooved on both sides, and fitted with hard pine splines, five-eighths by one and one-fourth inches. On the top of this a hard pine 1¼ inch floor was laid over a course of building paper.

Another method, which is certainly more novel than either of the others, consists in supporting a floor upon a bed of resin. The underlying earth was removed, and replaced with spent moulding sand, leaving trenches for the floor timbers, which were placed upon bricks laid without mortar. Melted resin was poured into the space alongside and underneath the timbers. The floor planks were then laid upon the timbers, the tops of which were about half an inch above the level of the sand. Holes were bored into the floor plank about four feet apart, and melted resin then poured into the holes, so as to interpose a layer of resin underneath the floor plank and beams. Upon this floor a top floor of hard wood was laid in the usual manner. This floor has been used for a number of years to support a large quantity of heavy machine tools, principally planers, without yielding or depreciation due to decay, and has proved to be most satisfactory.

In some instances asphaltum or coal tar concrete floors are not covered with wood, although it is much more agreeable for the help to stand upon wooden floors. It should be remembered that all these compounds are readily softened by means of oil, and they should be protected from oil by a coat of paint when not covered with wood; the preferable method being to first apply a priming containing very little oil, or a coat of shellac, and follow with some paint mixed up with boiled linseed oil.

(To be continued.)