The Chair: of setting, and it is thawed. Mr. Adler:

Freezing sometimes will suspend the operation cement will sometimes preserve its elasticity after

Provided it is not meddled with.

Mr. Kerr: In this particular case I am satisfied that this cement, which I believe was the Louisville cement, had actually set at that time. I do not know of course what difference there may have been in the ultimate strength.

The Chair: I had an experience some years ago with natural cement, in a case where it was used simply for the weight which the cement furnished; that it should have enough elasticity to stay together and form an anchor. The mass was something like 10X12 feet in a vertical direction, and about sixty feet in length, and was the anchor for a shear leg crane which was erected at the ship yards at South Chicago, but its whole office was simply to lay on the ground and hold itself down, so that the question did not come up of the hardness of the product or its ability to bear weight, no more than that the anchorage should not pull through it, as the weights coming on it were very heavy, something like 200 tons. Conditions were such that we were obliged to get the crane in operation to place some boilers in a ship that was being built at the yards, and we had to push the work when the temperature was from zero to fifteen degrees below zero. Well, we used ordinary precautions and mixed it with hot water and kept our sand as warm as we could considering the weather, and the stone in the same way, and dumped it through a spout into the hole, and at the end we filled up the hole with water, it would freeze over, when we would take of the covering five or six inches of ice had to be taken off, and we would go on with the work. That was left in that shape till next spring. I do not recommend this as a mode of construction with concrete, but at the same time it shows the result. Along in June I was called to the yard one day, was told that the foundation was all falling down, the anchorage of the shear legs was all falling to pieces. I went down there and found that the ground was all caving in around the crane, and by digging down a little way we found snow and ice where it had been dumped outside of the sheeting, and covered over. It was shoveled out and we heard no more of it for about six months; then we undertook to channel across that block of concrete to get another bearing to run a pipe through, and we had to do it with a cold chisel all the way through. That was simply a single experience in the way of misuse of cement, if you please.

Mr. Windett: At the South works of the Illinois Steel Co. there were two retaining walls put in about sixty-six feet long by two feet wide, exposed to the atmosphere about four feet. These were put in about a year ago, and they passed through the winter exposed to the weather, and at present I have not noticed any cracks on the face. A year ago last February, when the weather

for a week or ten days was down around zero, running somewhat below, we put up an addition to the rail mill at the southern part of the building, which foundation carries traveling cranes of twenty-five ton capacity in daily use. Those foundations were put in with slag cement, and broken slag for stone, and we have had no trouble whatever from the settling or cracking or deterioration of the foundation in any way at all.

XXXII

FIRE-PROOF CONSTRUCTION AND PREVENTION OF

CORROSION.

By GEN. WILLIAM SOOY SMITH, Mem. W. S. E.

Read April 6, 1898.

The use of combustible materials in buildings of all kinds endangers life and property to an extent realized only when we are startled into thinking by some great conflagration or appalling destruction of life by fire.

When a dozen or two of people, unable to escape from a burning building, or two or three firemen nobly battling with the flames, are burned to death, we read a notice of the deplorable event in our daily paper and exclaim, "It is awful," or "It's too bad," and pass on to the latest news or to spicy society gossip and think no more of occurrences which from their very frequency cease to make deep and lasting impressions. But if the great aggregate of destruction of life and property by fire during a single year could be carefully and accurately made up, the world would stand aghast at the horrible revelation.

While such wonderful progress has been made during the latter half of the nineteenth century in the development and applications of physical science, is it not passing strange that so little has been done to mitigate this stupendous evil?

The term "fire-proof" is only relative, for there is scarcely anything that will resist the highest known temperatures if applied for a few hours only. And the best and cheapest materials used in buildings do not belong to this class of very refractory substances.

The evil can be mitigated or prevented by the best possible protection that can be given to these by fire-proofing, and by preventing the very high temperatures that might otherwise be developed by fires by admitting only the very smallest quantities of more combustible materials, both in the construction of the buildings themselves and in their contents.

Even in the construction of small houses a cheap wooden frame can be erected and covered, both inside and out, roof and all, with a first-class fire-proof plaster that will stand exposure to weather and make dwellings that will be cheap, fire-proof, warm in winter and cool in summer, needing no painting, and which will be practically as durable as brick or stone houses.

Larger buildings may be constructed in like manner, and even brick and stone structures may be so plastered and made fireproof, and be otherwise greatly improved.

The subject of buildings is of vital interest to all mankind. Our convenience, comfort, health and safety depend largely upon the character of our dwellings and of the buildings in which our labor is done and our business transacted. It is especially requisite that the materials employed and the modes of construction of buildings shall be such as to make them strong, durable, safe and economical. They should also be as nearly as possible proof against destruction by fire, or by fire and water combined, as they are generally exposed to the joint action of the two in cases of conflagration.

The "skeleton construction" now so common in large cities for tall buildings is about as faulty and objectionable as it can be when exposed to this combined action. The expansion of the steel the buildings contain is at the rate of a tenth of an inch per foot for a change in temperature of one thousand degrees (red heat). The other materials, stone, brick, terra cotta, etc., each has its own rate of expansion differing from each other and from that of steel. They all differ also in their conductivity of heat. If these materials and steel are raised in temperature equally throughout their whole length, the increase in length will differ in each material, and taking the conditions as they occur in almost all burnings of buildings, the steel will, on this account, be heated much more quickly, and throughout a much greater part of its length, than any of the other materials present. The differences in the total dimensions of the several parts of the building resulting from these causes is so great as to bring about a destructive war between them. This is not mere theory, although it is correct. Close observation of the effects of fire on buildings discloses the same facts.

When a fire is in progress in a building and its parts heated to a high temperature, the fire engines throw powerful streams of cold water on the heated materials, and most of those now commonly employed fly to pieces under this joint action of fire and water. So says Chief Swenie, of the Chicago fire department, and all who have become familiar with the effects of fire and water on building material. This is especially true of the light integument of terra cotta built around the steel columns of a skeleton building.

A. W. Smith, an expert tester, having served the writer for the last two years making tests of various so-called fire-proofing materials, makes the following report:

CHICAGO, April 5, 1898.

"During the time we were engaged in the effort to discover a perfect fire-proofing, I think that nearly, if not quite, every kind used here in the construction of buildings was thoroughly tested and none was perfect; some of them endured fire alone, some endured water, but all save one yielded to fire and water. The clay tile not only transmitted heat too readily, but also when

heated to a red heat and subjected to a jet of cold water went to pieces. I found one porous clay tile which withstood the test of red heat and cold water without yielding or cracking. It was a hollow porous tile made by Lehmann & Kohlsaat in the northwestern part of this city. The tile was about two inches thick and eight inches square. It took twenty-five minutes to heat this tile over a very hot flame so that the hand could not be borne on the top. I plastered a tile of this kind on both sides with a three-eighths inch coat of asbestic plaster and the transmission of heat was thereby so greatly retarded that when placed in the same heat for one and one-half hours the bare hand could be borne for a brief time without pain on top of the tile.

"I found one of the compounded fire-proof tile, made in this city, to be the best non-conductor, of heat I have ever seen. But it will not endure fire alone or fire and water, and is in my judgment lacking in strength for many of the purposes of fireproofing. It will literally burn up slowly, though it will not blaze. "As to these compounded kinds of fire-proofing, I believe it to be true that several of them will burn slowly. Some of them will soften nearly to the consistency of pulp even in cold water, and not one of them will endure the application of cold water when they are brought to a red heat.

"Our best results were obtained by plastering the Lehmann & Kohlsaat tile, a tile composed chiefly of asbestic.

"The asbestic fire-proofing, when used in connection with steel or expanded metal lath, works admirably for the protection of all the members of steel, iron or mill construction, while it is beyond all question unequaled as a wall plaster. The last statement has been frequently demonstrated in eastern cities and here in Chicago. The plaster is strong, practically indestructible by fire, and as a non-conductor of heat is simply wonderful.

"(Signed)

A. W. SMITH."

Iron and steel being the strongest materials used in the construction of buildings, and in proportion to the service to be performed one of the cheapest, have deservedly come to the front rapidly as a building material, particularly in the United States, for the very high buildings that have been erected in the business districts of large cities in which the high prices of lots make it advisable to secure the greatest rentable space practicable on a given area.

The experience previously gained in the construction of iron and steel bridges throughout the world prepared the way for the use of these metals in buildings, and to some extent developed correct methods of proportioning and connecting their parts. But it seems remarkable, in view of this experience, that such radical defects still creep into the details of iron and steel framing in buildings-such as the flimsy lug and bracket connection of beams and girders with the columns, the eccentricity of loads