If wooden floors are used in a chemical laboratory, they should be protected by wax, paraffin, or some such material. Wherever finances will permit, and especially in a brick, stone, or concrete building, the use of tile floors is strongly recommended.

Floors made of asphaltum are recommended by Professor Gill. "But," as he remarks, "there is danger that heavy tables, chairs, etc., will sink into the asphaltum and thus render them of unstable balance and out of level." This, he suggests, may be partly overcome by making wide foot rests for such tables. Naturally this sort of floor must be laid on the top of a close-fitting underfloor and separated from it by tarred paper, asbestos board, or some form of steel lath. In every case where a laboratory is on the second floor all possible leakage from water pipes or basins must be prevented, and this is best done by taking care in construction.

The late Doctor Baskerville, formerly of the College of the City of New York (Science n. s. 28, p. 665 f.), said:

In my opinion, the best material for floors which has been put forward is that which is known as lithoplast, devised by Dr. W. L. Dudley, of Vanderbilt University. It is essentially a paraffined sawdust-sand floor, with a magnesia cement. This flooring may be laid in any length and in one piece and offers many desirable qualities. The baseboard may be made as a part of this floor. There are no cracks. The presence of the sawdust allows of its expansion and contraction with changes of temperature and the coating of paraffin over it prevents its rotting or napping, which are objections put forward in opposition to sawdust. It may be tinted, polished, washed, or scrubbed. It can be repaired without having cracked points, and, furthermore, it allows nails and screws to be driven into it in much the same way as wood does.

When it comes to a consideration of the material to be used for the tops of the laboratory tables, a more difficult problem must be confronted. It is without doubt true that all, or nearly all, of the older tables used for this purpose had wooden tops, and as a result of habit in the making of other tables oak or some more expensive material was used and finished with much care for appearance sake. But, as all who have worked in a chemical laboratory know, it is only a matter of weeks until such tables are blistered, stained, or discolored until they are unsightly, and it seems unnecessary to use expensive lumber and go to the trouble of polishing and varnishing it, as is done with furniture in general. Good, clear pine, free from pitch, is about as serviceable as oak. Naturally, there is some danger in the use of wood, but it causes less breakage of test tubes and beakers than almost any other material used. It is not so cold as glass, tile, or slate, and hence does not endanger glass apparatus as much.

Theoretically, plate glass is the most satisfactory material for table tops, for it does not stain, is easily kept clean, is nonabsorbent, is not affected by acids in ordinary use, and from the standpoint of wear

is durable. The only objections of serious importance that can be offered against the use of glass for this purpose are that it is cold and hard and is liable to crack from the heat reflected from the bottom of vessels heated during experimental work. This latter is such a serious objection that it seems wise to caution against its use. Professor Gill says:

For the tops of laboratory desks or tables the following woods have been found to give good satisfaction: Northern pine, whitewood, cedar, and California redwood. These may be finished with equal parts of linseed oil and turpentine, or better, filled with aniline black made in the pores of the wood.

It may be added here that sugar pine is an ideal wood for table tops for laboratories, for this wood does not readily warp. It can be had in boards wide enough for a full top, and so will leave no cracks. It does not splinter, can be planed easily, readily takes the stain and filling noted above, and is not heavy. Unfortunately, the great trees from which such lumber is made are rapidly disappearing, and therefore the lumber is comparatively expensive.

Mr. Lincoln, of the Technical High School of Springfield, Mass., says that he prefers wood as material for table tops for beginners in chemistry on account of the danger of increased breakage with the use of harder surfaces, but personally prefers white glazed tiles if they can be laid so that they will not buckle. When wood is used, he prefers soft pine treated in the following way (which is the same as that recommended by Professor Gill):

Solution 1:

Recipe for treating tops of laboratory tables.

100 grams aniline hydrochloride,

40 grams ammonium chloride,

650 grams water.

Solution 2:

100 grams copper sulphate,

50 grams potassium chlorate,

615 grams water.

Apply solution 1, let it dry, then apply solution 2 and let it dry. Do this three times.

During this process the color changes from green to black. The table top is then washed with hot soap solution, allowed to dry, then rubbed down with vaseline. After this last the color of the table top is a soft deep black.

The tables treated as above have given very good service. They are wiped with a damp cloth each day after the laboratory work is over.

WALLS.

In a chemical laboratory it is important that the walls be so constructed that the material composing them will neither discolor nor disintegrate as a result of the fumes liberated in experimental work. The ordinary plastered walls are very unsatisfactory, for

this disintegration begins quickly, and not only litters the floor but causes the room to appear untidy as a result of the rough and stringy appearance of the plaster. In laboratories where any quantitive work is done this falling material will vitiate results and cause much trouble. In sections of the country where earthquakes occur the plastering so affected is likely to fall and is therefore dangerous. The same is true in the event of fire. The use of cement instead of ordinary plaster is followed by similar troubles.

Hard-glazed tiles are clean, durable, neat, and acid proof, and when carefully selected and well set are easily cleaned and are also attractive in appearance. Glazed white brick is still more to be desired, but is expensive, and for inner walls adds considerably to the strength necessary in the building. Unglazed bricks may be used, but need to be covered with an acid-proof white or creamcolored paint. Professor Gill recommends for such purpose a paint made of "sublimed lead (PbSO,), barytes, or zinc white, or preferably a mixture of these in about equal proportions."

On the whole, despite the added danger due to the inflammable material, a ceiling made of well-seasoned pine or maple, carefully tongued and grooved with the boards not more than 3 inches wide, blind nailed and then treated with acid-proof paint, seems best adapted to a chemical laboratory for high schools. This is, in its initial cost, more expensive than plaster, but in the end it is cheaper and much more satisfactory.

Where plaster must be used "white plaster, which has been given three coats of acid sulphur-proof paint, a combination of lithopone and zinc oxide, has proved satisfactory. Paints which contain lead oxide should be avoided. All metal ware which is likely to be exposed to any fumes whatever in the laboratory should be painted with an acid-proof paint."

In the plan presented to indicate the proper arrangement of the science rooms, it will be noticed that the main aisle is along the wall away from the windows, and along the track laid in the floor. The tables in the laboratories ought to be placed at right angles to the main aisle, with individual work spaces and plumbing on each side. This will insure good light and better classification of the workers. The secondary aisles between tables can be made as wide as space will permit; but they should be at least 5 feet.

Further discussion of the arrangement of science rooms seems unnecessary, for equipment and plumbing are matters which school authorities must settle for each individual case. This further point, however, ought to be emphasized: It is a serious menace to the health of the students to work in a chemical laboratory which is not provided with adequate means for carrying off the fumes and keeping

the air pure and clean. Therefore, directly above the tables upon which the experiments are performed ducts should be placed to carry off the gases liberated in the experimental work. In small laboratories gas jets kept burning within the main part of the duct will create a fairly good draft and in this way help to keep the air pure. But in a larger room where many students are engaged and the system of ducts rather complicated, it is best to place in the pipes between the roof and the ceiling a small exhaust fan with an electric motor attachment to be run during the laboratory periods. This fan must be firmly bedded so as not to jar or buzz while running, and the branching ducts must be as free as possible from sharp angles, and air-tight between the openings above the tables and the outer air above the roof.

XVI. ASSEMBLY ROOMS.

The assembly room, or aula, as it is called, is the center of school life for a German gymnasium. It is the place of all places in the school where artistic and even lavish decoration is the rule. It is the historic remnant of the days when churches and chapels were used as gathering places for students, and it has retained some of the religious atmosphere of those bygone days. They gather here for music, for worship, for lectures, for counsel, or for some celebration. Stained glass windows, beautiful mural paintings, tasteful pieces of statuary, and very frequently a pipe organ attest the fact that this room is designed to be used for important educational purposes.

We have made rapid progress in supplying assembly rooms for both high schools and grammar schools since the earlier edition of this bulletin was printed. The illustrations of assembly rooms herewith presented should arouse our pride, for they are as beautiful and commodious as many of our best theaters. But for our smaller and medium-sized high schools we are not yet demanding what we should in this regard. It is earnestly hoped that the illustrations here reproduced will serve to stimulate to further efforts to secure for all schools this much needed and very helpful agency.

There is no desire to overestimate the need of assembly rooms in the American public high school, but I believe there is no country in the world where the need of social unification, artistic refinement, and cooperation is more pressing than in our country, under our form of government. Loyalty to athletic prowess is a good thing, but there is need for a deeper, more fundamental loyalty to school, to scholarly ideals, and to the community; and an artistic assembly room will greatly contribute to these ends. Every high-school building, then, ought to be built to meet this need. In addition to the uses above

suggested it will be a great stimulus to boys and girls in the grades if they also can occasionally share in the use of these rooms. Wise supervision of city schools demands closer contact between the children of the grades, especially the upper grades, and those of the high school. It would be a powerful stimulus to many boys to endeavor to enter the high school if now and then they could get a peep into the laboratories and assembly rooms of which they sometimes hear but which they rarely or never see. Moreover, around the school, as has been suggested, are gathering many organizations for social service looking to immediate help in practical citizenship. An assembly room, properly and tenaciously guarded against those who have selfish ends to serve, can become the rallying point for the general educational movements in the community. Such use of a school building will not desecrate it, and can, if wisely directed, be of great service in connecting school work with the real and vital problems of the community.

Having said so much in general-and these arguments are often needed to convince those in authority of the importance of supplying an assembly room-let us now turn to the actual demands of construction.

The first question to consider is its location in the building. The prevailing practice in the older buildings was to put it on the second floor, but this is passing away, for surely the first floor is a better place. This location saves much wear on the building, in that it enables large audiences to gather without threading hallways or climbing stairs. It makes it easier to start the day's work with an assembly, and in this way gives opportunities for announcements by the principal, for the inspiration of song, readings, or short addresses. It is safer in case of fire; permits of easy entrance from the second floor to the gallery, if one is introduced; and allows ample height for the stage and for the ceiling above the gallery without interfering with a uniform scheme for roofing. It also insures a safer and stronger building for large audiences and gives a better opportunity to heat and ventilate it properly. By thus using the height of two stories, the floor of the main room as well as that of the gallery can be inclined without interfering with any other part of the structure, and extra exits can be arranged with little expense and without marring the architectural effect of the building as a whole. This position will also have the advantage of the wider hallways, and exits below and will thus avoid crowding in the halls and on the stairways. If situated in the central axis of the building and opposite the main entrance, it will give a unity and dignity to the interior not possible when on the second floor. The floor plans and cuts herewith presented illustrate the arrange