of a building, will receive the plaster and hold it admirably while adding also greatly to the strength and stiffness of the frame. Strong floors and ceilings can be made by the use of this same form of lath and trough flooring.

The great weight of tile, brick and stone now used would thus be dispensed with and the much lighter construction described substituted. A very great saving of weight in the frame itself would be saved and the cost of the necessary foundations of the buildings be greatly reduced.

There would be so many other important advantages realized that we need not describe them here.

Enough has been said to invite the careful and unprejudiced study and criticism of engineers and architects, and out of this kind of investigation there may come a new system of building that may be the ideal one of the future.

XXXIII

FIRE-PROOFING OF WAREHOUSES.

By Mr. FRANK B. ABBOTT.

Read April 6, 1898.

Our modern steel skeleton building marks an era in the history of architecture. In pre-historic times, in the Druidical epoch, if I may be permitted the term, the architect practicing without a license but still building wisely and well according to his light, and with the primitive material then available, set up on end, at regular intervals, rough hewn or nature shaped posts of stone. Upon these posts and spanning the intervening spaces he laid other pieces of stone; upon these horizontal pieces he laid wooden poles, covering the whole with leaves and grass, and right here the simple principles underlying all architectural form were born-the column and the lintel. Through all the ages that have intervened we have not improved much upon these principles. We have varied them, it is true, we have used various materials from which to construct these two primary members, we have embellished them, we have placed a basket with Acanthus leaves growing around it on top of the column, we have inscribed the names of dead heroes on the lintels, but the column is a column still and the lintel is still a lintel, and while some of our profession seem never to have heard the old adage, “Ornament construction, but do not construct ornament," and in violation of the adage have at times almost concealed the true functions of column and lintel, still the two supporting members remain and wil remain until the end of time, or until nature rearranges her laws These two members are about all there is in a building aside from the finish and embellishment, for the beams and girders are but ramifications of the lintel, and struts and pilasters only undeveloped columns.

I repeat that the steel skeleton building marks an architectural epoch. The Romans marked an epoch when they introduced the arch and religion marked another when it drew the arch together at the top pointing up to heaven, but the use of steel has brought us back to earth, and with this new material we are starting again where the Druids did thousands of years ago. But we have the advantage of them, for a good many mistakes have been made in building construction since they set up the first column, and we are profiting by these mistakes. In those and in later times, the column could not be high without being pretty thick, and the lintel could not be long without being pretty deep, so the spaces between the columns were short, and

the Romans tried a curved lintel made of Voussoirs in order to overcome the difficulty.

But today we are back to first principles and are working out the same problems, so far as structural members are concerned, as were the Druids and the Greeks, but with the advantage of all that learning, science and experience has evolved in the intervening years; that is to say, the legs and ribs and backbone of our buildings are of steel today instead of stone or wood, because steel is stronger, and columns and lintels made of it are less limited in height and length, because carrying equal loads it is smaller in sections, because it can be readily worked into a thousand forms and when put together in a building becomes as one piece, a unit, without joints or seams, reaching higher toward heaven than the pointed arches of the old cathedrals.

You then naturally remark, "Steel must be the best building material," and I reply, "It is the best if properly handled." "But," you say, "why does not every one use it in building operations?" Every one will use it; it is only a question of time. It is only a question of time when all buildings will be built of this material, residences, churches, warehouses.

Our navy today is all steel, from keel to turret, and our residences and business buildings will be all steel in the near future, and not fire-traps for the destruction of life and property.

The word "fire" reminds me that I was not expected to talk about architecture, or about steel construction of buildings, but about fire-proofing. The preceding remarks are intended as a preface to the subject-matter. It is needless to say that fireproofing wooden construction is a paradox and a delusion, and fire-proofing stone absurd; therefore, it is assumed that when we speak of fire-proofing, we mean protecting steel and iron from the attacks of fire, for while steel is the best building material, it has two enemies, and in the light of recent discoveries it is difficult to say which is the greater.

Investigations recently made by the American Society of Mechanical Engineers, as to the condition of the steel in the frames of modern office buildings, reports of which investigations were published in Volumes XV and XVI of their transactions, show that in many instances the metal had been seriously attacked by corrosion, and there is small room for doubt that were the tile and terra cotta coverings removed from the steel skeletons of our great modern buildings, we should find that rust had set up its dangerous work in many places. Putting a covering over the metal and calling this covering fire-proofing does not insure the metal against corrosion, and sometimes, unfortunately, not against fire. Fire and corrosion, then, are the enemies of steel-the one bold, flagrant, irresistible, the other unseen, silent, insidious. Now, if we can keep these two enemies at bay, we have a perfect and enduring building.

To prevent corrosion of the metal is not a difficult matter, as it is only necessary to keep out oxygen and moisture. But I wish to remark, in passing, that painting the metal is but a short-lived protection, as wherever air currents occur along the steel members-as is frequently the case where hollow air spaces are left between the fire-proof covering and the steel, particularly where these air currents originate in basements or areas where there is moisture and warmth combined-the painting will protect the metal but a few months.

Now, a fire-proofing material, of whatever kind it may be, to properly perform its work must entirely cover the metal on every side, wholly envelope it, and be of such nature and thickness as will prevent the transmission of heat. This being so, it follows that, if this fire-proofing material has the further quality of being impervious to air or moisture, we can then successfully resist the two enemies of steel in buildings with one material.

So far, history shows that iron embedded in cement and conpreserved from rust, as for example, iron cramps laid in cement joints, and used to hold together the lintels of the Parthenon have been found intact, and anchors imbedded in the concrete of the walls of the Coliseum of Rome when brought to light are as bright and untarnished as when new, and coming down to our own times, we bury the steel beams of foundations in concrete to prevent the action of rust, and the inside of the bottoms of the steel ships of our navy are protected from rust by a covering of Portland cement.

Therefore, if our fire-proofing material is concrete, and wholly protects the metal from fire, it will preserve it from rust. The proposition advanced, then, is to surround every column, beam, strut or other structural member with concrete, and not only surround the metal, but envelope it on every side, leaving no air spaces externally or internally.

What kind of concrete is best for the purpose? My experience shows that the best concrete is, first, one that is a fire resistant; second, one that will not expand under the action of heat; third, one that is light; fourth, one that is sufficiently strong for the purpose; fifth, one that is high in lime. There are a number of substances which, mixed with mortar of cement, will make concrete which conforms in the main requirements to that above described, but they are more or less dense and therefore heavy. In the ten-story manufacturing building, 171-173 Canal street, Chicago, the concrete fire and rust proofing is made of soft coal cinders mixed with Louisville cement, in the proportion of four of cinders to one of cement. These floors weigh about thirty-five

pounds per square foot.

The lime of commerce is one of the best fire resistants known, and concrete for fire-proofing purposes is best that contains the greatest proportion of this ingredient consistent with strength. In the Druecker warehouse, now being built, the columns will be

protected by concrete made of one part natural rock cement, one part lime putty and four parts cinders. This concrete material will be rammed into the internal cavities, as well as entirely surround the columns, the nearest approach of the metal to the air being four inches when the column is finished. After the concrete is set it will be covered by a metal lath, on which will be spread a thick coat of dense hard mortar. Wooden cylinders, four feet long and made of two-inch staves, hinged so as to open in the direction of their length, will be set around the columns and the concrete rammed into place from the top. As soon as one four-foot section is concreted the second section is constructed on top of the first, and this process continued to the top of the column before floors are put in, thus securing a continuous envelope to the column, without joint from basement to roof. The metal lath is used to provide a better key for the mortar finish and to protect the concrete from possible injury under high temperatures.

The steel will have no painting whatever, but will be cleaned of mill scale and other foreign substances at the building, before concreting, as nothing should be put upon the steel to prevent the perfect adhesion of the cement to the metal, as the cement in the concrete settles about the metal and deposits upon its surface a coating while the concrete is being rammed into place. The external columns will be covered with hollow bricks, and the spaces inside this outside covering filled with concrete material, the same as other columns.

In any building during a fire the point most fiercely assailed by the heat and flames is the floor construction directly above the fire, and there has been plenty of evidence to support the statement that if the floor construction of any building is impregnable to fire which may occur or originate in any story, then the damage from fire in such a building will be slight so far as the building itself is concerned. The fierce heat generated in burning buildings is caused by the floors burning away and thereby creating a draught through several stories.

To make a building fire-proof we must so construct the floors that fire cannot get through them, and in this connection it is perhaps well to say that there should be no openings of any kind whatever through the floors in buildings used for warehouse purposes, and all stairs and elevators should be enclosed in solid brick shafts.

In the Druecker warehouse the floors will be made wholly of cinder concrete put in as arches between the beams, and so constructed as to give 4 inches of concrete on the lower flanges and 3 inches on the upper, and the underside of all floor construction, meaning the ceilings, will be covered as are the columns with metal lath and plastered with hard mortar. The accompanying details show the method of application.

This concrete floor construction serves also another useful pur