use ice for preserving their milk, and thus of necessity keep it at a sufficiently low temperature, yet there are quite a number who produce and sell their milk without even depriving it of the animal heat. This can not but cause serious trouble to infants, and should, therefore, be prohibited.

In addition to the analyses set forth in the summary, I have also inspected about 60 dairies, which, together with the examination of the ventilation in the public schools, has constituted the year's work. Very respectfully submitted.

J. D. HIRD, M. A., Chemist.

Dr. W. C. WOODWARD,

Health Officer.

HEATING AND VENTILATING OF CERTAIN SCHOOL BUILDINGS.

In compliance with your instructions I have the honor to submit the following special report relative to the investigation into the heating and ventilating of certain school buildings:

For several years this subject has been receiving considerable attention, it being generally recognized that in order to have a sound mind within a sound body it is essential that the developing mind and body should be surrounded by conditions favorable to their healthy growth; and it is further recognized that the most important condition essential to this development is a generous supply of pure, fresh air. This fact hardly needs demonstration, for it is well known that every human being, in order to live, must be constantly breathing, and that in the act of breathing he takes in oxygen and throws out from the lungs not only carbonic acid gas, but also organic matter. This organic matter consists of epithelium, molecular, and cellular matter, which, owing to its being saturated with moisture, is in a condition most ready to putrefy. It is chiefly owing to this organic matter in air which has been breathed that injury arises, for while one could not live in an atmosphere of carbonic acid gas, one would experience little difficulty in an atmosphere containing as small an amount of the gas as is usually found in crowded rooms, provided this organic matter was absent, for it is estimated that the air would have to be vitiated to the extent of 5 per cent of carbonic acid gas in order to destroy life.

The ill effects produced, therefore, by breathed air must be due, for the most part, to the contained organic matter.

The first requisite of the schoolroom, therefore, as above stated, is a generous supply of fresh air, and the means by which this may be obtained at a proper temperature, without creating unnecessary and unpleasant drafts, is the problem which is engaging the attention of sanitary officers and engineers.

A second requisite, as an adjunct to the first, is a sufficient amount of floor and cubic space, for the smaller the space allotted to each individual the more rapid must be the change of air, which change, if too rapid, will necessarily cause unpleasant drafts.

In addition to these considerations, we have many other conditions affecting the health and comfort of the individual which it is our purpose to consider at this time, basing our conclusions upon the result of the investigations made, and trusting that honest criticism, where necessary, will assist us to a better knowledge of those conditions and means for their betterment which influence to a large extent the health of a

Location of buildings.-The first subject that needs consideration, in the discussion of the sanitary condition of the public schools, is the location of the buildings. Little need be said here concerning this subject, except to emphasize the fact that proximity to manufacturing establishments, steam railroads, or any other corporation whose business requires production of noise, smoke, or the generation of odors, is to be avoided.

The object to be obtained is cleanly and quiet environments, pure air, and plenty of ground where the children may run and exercise their lungs during the time of intermission and which will permit the building to be properly lighted.

Size of rooms.-The size of the schoolrooms in the public school buildings of this District varies somewhat, although they are on an average about 14 feet high by 25 feet wide and from 32 to 35 feet in length. They are planned to seat about 48 pupils, although the capacity of some of the rooms is greater. I have, therefore, estimated the seating capacity of the various rooms at 50 each, and have based my estimates of the floor and cubic space per individual on that number.

The best American and European authorities agree that there should be not less than 250 cubic feet of space for each individual. Taking this figure, therefore, for our standard, we will note from the table that except in two instances this figure is closely approximated in all the buildings examined, and that where the cloakroom is included in the estimate, this figure is considerably exceeded. Consequently, so far as the cubic capacity of the rooms is concerned, it is fair to presume that they meet the necessary requirements.

Heating and ventilation.-Heating and ventilation are closely allied to one another, and are practically part of one and the same process, except where stoves or direct steam radiation is relied upon for heating.

The object to be attained must necessarily be the introduction of heat sufficient to maintain a constant and proper temperature in the schoolrooms, and to provide for a sufficient supply of fresh air and the removal of the vitiated air.

There are practically three methods by which this may be accomplished either in whole or in part.

One is by direct steam radiation, which, considering the subject of heat alone, is all that could be desired. The trouble here, however, lies in the fact that we get little or no ventilation, or only such as would be caused by the escape of the heated air around the doors and windows and its consequent replacement by cooler air.

The second method is by means of what is known as the direct-indirect system, which allows fresh air from the outside to flow around the radi ators, thus insuring the delivery of pure heated air, and not such as may have been breathed once or twice, as in the case of direct radiation. The trouble here, however, lies in properly regulating the supply of air, for when the heat is reduced the supply of air is reduced also, while on other occasions, if the wind is in the direction toward the inlets, it is somewhat difficult to heat the air, owing to the limited area of heating surface.

The third method, and probably the most satisfactory one of the three, is by what is known as the indirect system, in which fresh air from the outside is allowed to flow around and through the furnace, or around steam coils and then to pass on by means of appropriate ducts into the rooms above.

As this method more properly combines the systems of heating and ventilation, and it has been pretty generally adopted in the more modern

type of school buildings, it is fitting that we should give it our par ticular attention, in order that we may note its defects and make such improvements therein as may seem desirable and expedient.

Two of the buildings of this class which were examined, the Douglass and Greenleaf, are provided with fans for attaining this object, but the remainder depend upon heat for the motive power. Heated air rises, and this is the sole principle of heating and ventilating in all the schools with the exception of the two mentioned and one other. In these buildings, as above stated, fans are used for forcing the air into the rooms above, thus being independent of outside influences, such as the direc tion and velocity of the wind and the various conditions of the weather. In the other buildings of this class, however, which depend upon indirect heat, it will be seen that the weather plays an important part, for the system consists of a window for the introduction of fresh air, furnaces or steam-coils for heating the same, and ducts for conveying it to the rooms above. To remove the air from the rooms one or two systems are in general use; either the air is allowed to escape through ventilators and make its exit up the chimney, or, as in the case of the Smead system, the same principle is used for removing the air as for supplying it, namely, a stack heater is so arranged as to heat the air in a chimney whose supply of air can only be obtained from the rooms. It thus acts as an aspirator to the rooms, by causing the heated air to pass up the chimney and drawing other air from the rooms to supply its place. To accomplish this a line of ventilators, each about 3 feet long and 4 inches high, are placed along the base of the floor, usually one under each window.

The Smead system.-With this system it will readily be seen that unless fans are used for forcing the air its successful operation depends, to a considerable extent, upon the direction and velocity of the wind; upon the degree of heat generated by the furnaces, and, indirectly, upon the temperature of the outside air, for the warmer the air the less the fire that will be kept in the furnace, and, consequently, the less the quantity of heated air that will rise to the rooms above, until when the warmer months of spring arrive and the furnace fires are allowed to go out the amount of fresh air entering the rooms from this source becomes very slight.

Then, again, should the winds be blowing in a direction away from the fresh-air windows, there is not only a tendency to decrease the quantity of air entering there, but there is also a tendency to reverse the entire system by diminishing pressure in the neighborhood of these windows. So that at times it simply becomes a question as to the power of the two opposing elements, with the chances of a reversal of the current greatly strengthened after the fires in the furnaces have been allowed to go out and the main motive power thus removed. When, however, the wind is in the direction of the windows, then the velocity of the air entering the room is greatly increased, and the chances of a reversal of the current or of a backward draft are reduced to a minimum. In like manner the windows and doors also exert an influence on the successful working of this system, which will be better appreciated when we consider further the manner in which the air is removed from the rooms to the vent stack.

By consulting Plan A it will be seen that in the Smead system there are two stacks, each of which is required to act as a ventilating shaft for four rooms, two on the first floor and two corresponding rooms imme diately above on the second floor. The foul air on leaving the rooms