Now, gentlemen, if these men had not been prudent in this matter, and, instead of making this combination, had been extravagant in adopting the heavy iron and heavy clay as in the English system, they would have secured improvements in name, but not in fact; for cash is the key to the situation, and, although the manufacturer has noble aspirations for progress and improvement, he knows that he must maintain prudential limits.

I have enlarged on this point; for it is a general defect, that, when we see a new thing, our natural inclination is to go to the extreme and reach after the impracticable, thus making no progress.

Thus was established in Catalonia two systems of fireproof factories: the one type shown in the factory of Vidal Hijos, constructed 1871, the spindle building of Battlo Bros., 1869, and several others; the other type shown in the loom room of Battlo Bros., woollen factory of Carreras, etc. The first type consists of wooden girders and tile arches, and the second has tile arches for ribs, with small iron beams with dome between. Sections shown on plan.

What is the combination, -iron and clay, or wood and clay? It is very simple; it is only iron or wooden girders, set apart over columns at the regular distance of a factory bay, ten feet six inches or more, as has been stated, and between them tile arches, similar to those now to be seen in the Boston new public library, or the Harcourt building, or Exeter Chambers.

The combination with iron can be executed in two ways, as it is used in some of the rooms of the library, acting as a beam or girder, working by deflection; or as used in the Colorado Telephone Company's building, Denver, Y. W. C. A., New York, working principally by tension. This latter form may also be seen in some of the rooms of the library. When the combination is of wood, it is working in deflection, as in the case of iron, and in some cases by tension. The construction is cheapest in both materials when working by tension.

Some may think that fire-proofing in Catalonia is cheaper than here; that, in a general sense, is not so, because, supposing they had accepted the English system, the relation between the English system and the cohesive system would be the same there as here. It may be supposed that the cohesive system is dearer here than there. I will show wherein the difference lies. It cannot be in labor, as the same proportion of difference exists in the wages of carpenters for wooden construction as for masons; and, as the walls are the same in either case, the difference is only in the floors; and, if any there be, it must be in the material. Wood is the same there as here. Portland cement, one of the main factors in the construction, costs in Spain three dollars a barrel, against two and one-half dollars here. Plaster costs about the same. The difference is only in the cost of the tile, which in Spain can be purchased at five dollars per thousand, while costing here fifteen dollars; but, taking into consideration the fact that in Spain we use fiveeighths inch and here one inch in thickness, and that the tile is only one of the components, and that it is only in this special material that the cost is greater, the real difference in the price per foot of the material is only twenty-five per cent. This twenty-five per cent. difference in the cost of materials cannot be a sufficient reason for not using the construction here; for, in a factory one hundred by one hundred feet, or ten thousand square feet, the difference in the floors would only be eight hundred dollars. I do not think this eight hundred dollars would prove an insurmountable obstacle to a New England manufacturer, therefore this cannot be the cause. In the iron there is a little disproportion; but, as the economic state of a country is relative in all things, if the iron and construction is cheaper, the production is also cheaper and the income and interest less, so that does not affect this comparison; consequently, the difference in cost there and here between the wooden and fire-proof factories is really the same, and the reason for not adopting the same system here is not due to the difference of eight hundred dollars for each ten thousand feet of floor.

We can now build the arches sufficiently light and strong with enough span to bridge a large bay, and can use iron girders or wood, with clay. Both of these have their advantages, especially the latter:

First. Avoiding heavy construction of brick.

Second. Enlarging the span so as to bridge from bay to bay ten, twelve, fifteen feet or more.

Third. Avoiding the inconvenience in setting shafting, giving the same facilities as though all wood.

As regards the arches themselves, they can be seen in every form and combination in the new library, as was explained in my lecture in this building of Oct. 24, 1889. This construction consists of a combination of clay tiles and Portland cement, forming in itself an artificial stone of the shape which experience advises, selecting in each case the most convenient form, knowing that on this depends the economy and strength of the arch. To give a more practical idea of this element of construction, I may say that it is nothing more than a conglomerate; and I think that you are all aware of what the term conglomerate implies, that is, a stone composed of small chips united together by nature with sediments of lime, silicate or aluminum, or a combination of these. We have examples of this all about Boston; the principle is the same, the only difference is in the process or modus operandi, so as to obtain rapidity, economy and lightness inside of the maximum strength, and to secure this we use clay tiles and Portland cement, forming practically an artificial stone.

CRITICISMS ON THE SYSTEM.

Many discussions have arisen both in favor of and against the cohesive system in the last months, as is natural when any new application is brought forward in the arena of scientific discussion; but it is frequently seen that the greatest friends of the system sometimes go too far in their enthusiasm and favor of the new idea, the result being that in their hands it is disfigured or erroneous.

For instance, it is said:

First. That the arches under this system have no thrust. This is correct, and not correct, as I will prove afterwards.

Second. It is said that the system is more expensive than any other system of fire-proofing, or that there is no economy in it. To this I will answer that it depends on the forms adopted in the system.

Third. That the ceilings of this construction require greater height than others; consequently, it is necessary to

build every room with high ceilings, and this of course causes the building to be higher. That seems to be so, surely, because some people may have seen some arches or ceilings that have been constructed specially with a high rise, to give more constructive lines; and they thought that all the ceilings must have a similar rise; when the truth is, that it entirely depends on the wishes of the architect who is applying the system.

In answer to the first, I will say that the thrust depends on the form and not on the material. Suppose we take a lintel of stone, as in Fig. 1; if we put it as in Fig. 1, practically we have no thrust. If we take another lintel, Fig. 2, that is like the first one; but, taking off the material under the curved line A, B, C, Fig. 2, we have some thrust at once. You can see, without any demonstration, that in the second case we have thrust and in the first one we have comparatively none. This does not mean that in the first case it absolutely does not exist, because inside of any lintel we must consider an arch when it is working; in the same way that in any block of stone or any block of marble or any block of wood we know exists the most ideal figure that the imagination can conceive, the question is to take away the shell that involves it. In the same way in any piece of wood or in any block of stone we have an arch better than which the most exact mathematician cannot define; and, as soon as we put a lintel to work, this imaginary arch is put into action, and all of the material under this arch is working to take off the thrust, because it is the rod of this imaginary arch. Now, if we take away this material (which is the condition in the second case), as the material which is working as a rod is not there, the arch is more free for weight and thrust.

But we have a third case; suppose Fig. 3,- this is not a lintel where we take the lower part of the material forming, as in the rest, an arch, this is a regular arch, formed by pieces; it is not necessary to demonstrate that this has thrust, but in this case the thrust is in full; permit me to