* *
 
 International Ctuuatton j 
 
 EDITED BY 
 
 WILLIAM T. HARRIS, A. M., LL. D. 
 
 VOLUME IV.
 
 INTERNATIONAL EDUCATION SERIES. 
 
 EDITED BY W. T. HARRIS. 
 
 IT is proposed to publish, under the above title, a library for teachers 
 and school managers, and text-books for normal classes. The aim will 
 be to provide works of a useful practical character in the broadest sense. 
 
 The following conspectus will show the ground to be covered by the 
 series : 
 
 I. History Of Education. (A.) Original systems as ex- 
 pounded by their founders. (B.) Critical histories which set forth the 
 customs of the past and point out their advantages and defects, explain- 
 ing the grounds of their adoption, and also of their final disuse. 
 
 II. Educational Criticism. (A.) The noteworthy arraign- 
 ments which educational reformers have put forth against existing sys- 
 tems : these compose the classics of pedagogy. (B.) The critical histories 
 above mentioned. 
 
 III. Systematic Treatises on the Theory of Edu- 
 cation. (A.) Works written from the historical standpoint; these, 
 for the most part, show a tendency to justify the traditional course of 
 study and to defend the prevailing methods of instruction. (B.) Works 
 written from critical standpoints, and to a greater or less degree revolu- 
 tionary in their tendency. 
 
 IV. The Art Of Education. (A.) Works on instruction 
 and discipline, and the practical details of the school-room. (B.) Works 
 on the organization and supervision of schools. 
 
 Practical insight into the educational methods in vogue can not be 
 attained without a knowledge of the process by which they have come to 
 be established. For this reason it is proposed to give special prominence 
 to the history of the systems that have prevailed. 
 
 Again, since history is incompetent to furnish the ideal of the future, 
 it is necessary to devote large space to works of educational criticism. 
 Criticism is the purifying process by which ideals are rendered clear and 
 potent, so that progress becomes possible.
 
 History and criticism combined make possible a theory of the whole. 
 For, with an ideal toward which the entire movement tends, and an ac- 
 count of the phases that have appeared in time, the connected develop- 
 ment of the whole can be shown, and all united into one system. 
 
 Lastly, after the science, comes the practice. The art of education is 
 treated in special works devoted to the devices and technical details use- 
 ful in the school-room. 
 
 It is believed that the teacher does not need authority so much as in- 
 sight in matters of education. When he understands the theory of edu- 
 cation and the history of its growth, and has matured his own point 
 of view by careful study of the critical literature of education, then he is 
 competent to select or invent such practical devices as are best adapted 
 to his own wants. 
 
 The series will contain works from European as well as American 
 authors, and will be under the editorship of W. T. HARRIS, A. M., LL. D. 
 The price for the volumes of the series will be $1.60 for the larger 
 volumes, 76 cents for the smaller ones. 
 
 Vol. I. The Philosophy of Education. By Johann Karl 
 Friedrich Rosenkranz. 
 
 Vol. II. A History of Education. By Prof. F. V. N. Painter, 
 of Roanoke, Virginia. 
 
 VoL III. The Rise and Early Constitution of Univer- 
 sities. With a Survey of Mediaeval Education. By S. S. Laurie, 
 LL. D., Professor of the Institutes and History of Education in the 
 University of Edinburgh.
 
 INTERNATIONAL EDUCATION SERIES 
 
 THE 
 
 VENTILATION AND WARMING OF 
 SCHOOL BUILDINGS 
 
 BY 
 
 GILBERT B. MORRISON 
 
 TEACHER OF PUY81C8 AND CHEMISTRY IN KANSAS CITY HIGH-SCHOOL 
 
 NEW YORK 
 D. APPLETON AND COMPANY 
 
 1887
 
 COPYRIGHT, 1887, 
 BY D. APPLETON AND COMPANY.
 
 EDITOR'S PEEFAOE. 
 
 THE practical character of the present volume will 
 be at once manifest. Of the four departments of edu- 
 cational literature history, criticism, theory, and prac- 
 tice the last includes two classes of works : . 
 
 1. Those that relate to instruction and discipline, 
 and the details of teaching. Under this head come the 
 arrangement of the course of study, the programme of 
 daily work, the methods of teaching and discipline. 
 
 2. Those that relate to the organization and super- 
 vision of schools. Under this head we include works 
 relating to school legislation, governing boards, the 
 building of school-houses, and the organization of a 
 corps of teachers. 
 
 Of these practical matters practical because they 
 relate to the application of theory to details, and imply 
 the adaptation of means to ends the question of the 
 proper construction of school-houses is justly esteemed 
 to be of great importance. The school-house is a per- 
 manent affair. Other matters may be changed with less 
 ceremony ; a building stands for two or more genera- 
 tions. If it is faulty in its method of lighting, it will 
 send out every seven years its quota of children all
 
 yi EDITOR'S PREFACE. 
 
 affected more or less with a tendency to weakness of 
 eyes, near-sightedness, and to nervous dyspepsia and 
 irritability of temper. If the ventilation has been de- 
 fective, and a remedy has been sought by opening the 
 windows, so as to admit cold air from the bottom, the 
 seeds of future rheumatism and heart-disease have 
 been sowed. If the warming has been imperfect, a 
 long series of colds have weakened the lungs of pupils, 
 and many cases of consumption resulted. 
 
 The author truly remarks that " the greatest necessi- 
 ties are often not felt as wants." Our early experience 
 in a school-room that failed in these essential particu- 
 lars has left on our minds, perhaps, in most cases, the 
 impression that we did very well in the old-fashioned 
 school-house. We were not able then to trace causes 
 and effects in these matters on account of ignorance of 
 hygiene. We have seen evil enough befall our com- 
 panions in their life subsequent to the school, but it has 
 not occurred to us to trace it to the exposure incident 
 to improperly constructed school-buildings. 
 
 It is believed that the present work furnishes a good 
 text-book and book of reference to be used in normal 
 institutes and normal schools. A short course of lessons 
 or lectures will suffice to qualify a teacher to judge cor- 
 rectly in matters of ventilation, and to act efficiently 
 under all circumstances. When this is considered, it 
 will be seen that every corps of teachers should be 
 taught the theory and practice of warming and ven- 
 tilating according to the experimental or investigating 
 method. 
 
 I have drawn up the following syllabus of topics 
 and suggestions for a course of eight lessons, covering
 
 EDITOR'S PREFACE. yii 
 
 the most important items of the subject. I have also 
 added a full analysis of the contents of the volume : 
 
 LESSON I. The general principles of hygiene as re- 
 lated to ventilation. The necessity of pure air. Analy- 
 sis of air. What impurities are found in the air of 
 un ventilated school-rooms. Pasteur's experiments. Ef- 
 fect of breathing impure air stupor, headaches, diseases 
 of the lungs, dyspepsia, nervous affections, etc. (Chap- 
 ters I, H, III). 
 
 LESSON II. How to test the purity of the air (Chap- 
 ter IV). The proper degree of moisture in the air 
 73 per cent of saturation (Chapter III). How to test 
 the degree of humidity (Appendix A, page 161, Glai- 
 sher's factors). Amounts of moisture in the out-door 
 air at different temperatures (page 162) : at 80 Fahr., 
 elastic force 1-023 ; at 70, '733 ; at 50, -361 ; at 32, 
 181 ; at 20, -108 ; at zero, -OM. If out-door air at a 
 temperature of 20 Fahr. is heated in the school-room to 
 70 without adding moisture to it, it is seven times as 
 dry that is to say, its capacity to absorb moisture has 
 become seven times as great as before. Hence the dele- 
 terious effect on the mucous membrane of the air-pas- 
 sages and even on the skin of the body. 
 
 LESSON III. The proper amount of light for a 
 school-room. It should be lighted on two sides from 
 the rear of the pupils and from the left-hand side not 
 from the right-hand side, because of the shadow of the 
 hand upon the paper when writing or drawing. The 
 windows should extend to the top of the room, or at 
 least as high as one half the width of the room, in order 
 to light sufficiently the pupils sitting farthest from the 
 windows. Hence the room should not be too wide
 
 EDITOR'S PREFACE. 
 
 not over 24 or 28 feet when the windows extend 14 feet 
 above the floor. The length of the room may be 32 or 
 34 feet. There should be three windows on the side and 
 two at the end of the room. Double windows are very 
 desirable for ventilation purposes (Chapter X), and for 
 protection in very cold weather, when a current of 
 chilled air falls down the surface of the window. If a 
 room happens to be seated so that light comes from the 
 right hand of the pupil, the desks may be changed so 
 as to bring it from the left hand and rear. A school- 
 building is ill constructed if its rooms have windows on 
 one side only, unless the rooms are very narrow, and 
 receive light solely from the north, as such rooms are 
 sometimes constructed in Europe for advantages in 
 drawing-lessons. Rooms on the south, east, or west side 
 of the building must exclude the direct rays of the sun 
 during some portion of the day by curtains or shutters, 
 and the consequence is that pupils sitting remote from 
 the windows get too little light, unless thin white cur- 
 tains are used and the windows are very large, and in 
 height equal to two thirds the width of the room. 
 Pupils sitting in twilight (the shutters being closed) 
 become near-sighted in consequence of straining their 
 eyes, or because they acquire a habit of holding the 
 book too near the eyes. The correct form of school- 
 building requires four rooms to each story one on each 
 corner. Two or three stories at most is enough, and a 
 school-house should not stand nearer than 70 feet to 
 another building, on account of the obstruction to light 
 occasioned by it, especially to the rooms of the ground 
 story. 
 
 LESSON IV. The amount of air required per pupil
 
 EDITOR'S PREFACE. 
 
 IX 
 
 2,000 feet per hour (Chapter Y). The average school- 
 room, 28 x 34 x 14, with 50 pupils, furnishes fresh air 
 enough to last 7 minutes. Methods of calculating 
 the size of ventilators necessary, and the rapidity of the 
 movement of the currents of air admitted through 
 them (Chapter V). The registers for the entrance of 
 fresh air properly warmed should be distributed around 
 the room. Natural ventilation depends on the fact that 
 heated air is lighter and rises ; passing out of the top 
 of the room, it sucks in fresh air through the inlets 
 below (Chapters V and YI). The inlets should be 
 placed near the floor. Why 2 (Chapter YII.) Size of 
 flues admitting fresh air for 75 children 10 square 
 feet of total area. The foul-air flues should have an 
 equal area. Importance of frequent cleaning of the 
 foul-air shafts (Chapter YIII). 
 
 LESSON Y. Aspirating chimneys what they are, 
 and how large. The velocity of the column of air as- 
 cending to be 7'7 feet per second. Discuss the two 
 methods : (a) Drawing the foul air out of the bottom of 
 the room into the aspirating chimney ; (J) out of the 
 top of the room (Chapter IX). The theory that im- 
 pure air falls to the floor incorrect (Chapter YII). 
 Method of drawing down pure air through a ventilating 
 shaft. Necessity of heating the column of air in a foul- 
 air shaft to secure its efficient movement. The best 
 plan to build large aspirating chimneys with iron smoke- 
 stacks passing up through the center to heat the foul 
 air. 
 
 LESSON VI. Ventilation by windows (Chapter X). 
 Inconveniences of such ventilation dust, smoke, waste 
 of heat, cold drafts, etc. On account of defective plans
 
 x EDITOR'S PREFACE. 
 
 for school-buildings, 99 per cent of the school-houses 
 depend on windows and doors for ventilation. Always 
 lower the windows from the top, except when the out- 
 door temperature is above 80 Fahr., when they may 
 be also raised from the bottom. In very cold or windy 
 weather the windows should be lowered only one inch, 
 or even less ; in moderate weather 12 inches, or even 
 more. But all windows should be lowered alike, so as 
 to move all the air in the room ; otherwise the ventila- 
 tion will be very imperfect. If a window is opened 
 too wide in cold weather, a chilly current pours in 
 upon the necks and shoulders of children, and produces 
 colds or rheumatism. If the windows are lowered only 
 slightly, the cold fresh air moves down the surface of 
 the wall and gets warmed somewhat in its descent by 
 contact, with the heated air. The devices of oblique 
 boards fastened to the sash (Chapter X). The effects 
 of the wind when strong sometimes require the windows 
 on one side to be nearly or quite closed. 
 
 LESSON YII. The most efficient means of ventilat- 
 ing is a fan or blower (Chapter XII). It should be 
 placed in the flues for fresh warm air (plenum move- 
 ment), and not in the impure-air shaft (vacuum move- 
 ment) (pages 79 and 80). The action of Bittenger's 
 fan (pages 84^87 and Appendix C) ; of the Blackman 
 fan (Appendix F). The method of calculating the 
 efficiency of the aspirating chimney (Chapter XI and 
 Appendix B). 
 
 LESSON YIII. The proper temperature of a room, 
 70 Fahr. (Chapter XVI). General methods of warm- 
 ing : conduction, i. e., by stove-pipes ; convection, i. e., 
 by hot air from furnace or steam-coil ; radiation, i. e.,
 
 EDITOR'S PREFACE. xi 
 
 by open fire-place, standing coil, or stove. Importance 
 of using large stoves or furnaces to "avoid the neces- 
 sity of overheating. The poisonous gases that escape 
 through iron when heated to redness. Great advantage 
 of radiant heat. Nearest to solar heat. Dr. Arnott's 
 smokeless grate ; open fireplaces (Chapter XYII). The 
 Ruttan system. Advantages and disadvantages of steam 
 heating (Chapter XVIII). Direct radiation from steam- 
 coils not good for the school-room, because it does not 
 provide for moving the air of the room and for supply- 
 ing fresh air ; warms the same air over and over ; diffi- 
 cult to provide for moistening the air ; needs a ventilat- 
 ing fan to render it efficient. Prof. Morrison's ideal 
 plan for warming and ventilating ; distributes his steam- 
 coils underneath the floor with many small registers 
 opening into the aisles of the school-room; foul air 
 escapes at the top of the room into an aspirating chim- 
 ney.
 
 CONTENTS. 
 
 CHAP. PAOB 
 
 I. NEEDED INFORMATION 11 
 
 II. THE EFFECTS OF BREATHING IMPURE AIR . . .17 
 
 III. THE AIR 24 
 
 IV. EXAMINATION OF THE AIR 31 
 
 V. AMOUNT OF AIR REQUIRED 38 
 
 VI. GENERAL PRINCIPLES OF VENTILATION .... 45 
 
 VII. NATURAL VENTILATION 48 
 
 VIII. INLETS 61 
 
 IX. REGULATING THE DRAFT OF OPENINGS THE WIND. 56 
 
 X. VENTILATION BY WINDOWS 62 
 
 XL ARTIFICIAL VENTILATION 70 
 
 XII. THE MOVEMENT OF THE AIR BY MECHANICAL MEANS . 78 
 
 XIII. AIR-PROPELLERS 82 
 
 XIV. CAN THE PLENUM MOVEMENT BE AFFORDED ? . . ,90 
 
 XV. THE COST or VENTILATION 97 
 
 XVI. WARMING . .104 
 
 XVII. METHODS OF WARMING Ill 
 
 XVIII. STEAM HEATING 129 
 
 XIX. AN IDEAL PLAN FOR WARMING AND VENTILATING . . 144 
 APPENDIX A. METHOD OF TESTING THE HUMIDITY OF THE AIR . 160 
 
 B. ASPIRATING CHIMNEYS 163 
 
 C. RITTENGER'S FAN (page 84) 166 
 
 D. CONDUCTING POWER OF MATERIAL . . . .167 
 E. RADIATING AND ABSORBING POWER OF MATERIALS . 168 
 F. THE BLACKMAN FAN 169
 
 ANALYSIS OF CONTENTS. 
 
 CHAPTER I. Needed Information. Advice plentiful (p. 11); questions 
 to be answered regarding impure air where found, its causes, its reme- 
 dies ; most of the school-houses in the United States made without atten- 
 tion to ventilation (p. 12); they depend on loose-fitting windows and 
 doors for fresh air ; report of the commission appointed by Congress on 
 the public-school buildings in the District of Columbia (p. 13) ; systems 
 of warming and ventilating in Boston, Denver, London, Vienna (p. 14) ; 
 authorities consulted, R. S. Roeschlaub, Professors Parkes and Draper, 
 Dr. de Chaumont, General Moran ; Dr. Neil Arnott (p. 15) and his la- 
 bors (p. 16). 
 
 CHAPTER II. The Effects of Breathing Impure Air. Symptoms caused 
 by breathing impure air; stupor, headache, etc. (p. 17); not the carbonic 
 dioxide, but the poisonous emanations from the skin and lungs (p. 18); 
 bad air the cause of consumption ; authorities and statistics ; ventilation on 
 ships ; New York Board of Health attributes 40 per cent of all deaths to 
 breathing impure air (p. 21) ; effect of bad air on the work of the pupils 
 and on their behavior (p. 22) ; financial waste in neglecting ventilation 
 (p. 23). 
 
 CHAPTEB III. The Air. Its composition : contains carbonic dioxide, 
 even in its pure state, one part in 2,600 (p. 24). Its impurities: their di- 
 lution in the air, diffusion ; ammonia the great supporter of microscopic 
 animals, 200 forms of them found in the air ; Koch's and Pasteur's ex- 
 periments (p. 26) ; street-dust near the ground contained 45 per cent of 
 organic matter and 30 per cent at a height of 134 feet; ground air 
 unwholesome; air poisoned by stoves and heating apparatus (p. 27). 
 Humidity of the air: importance of supplying moisture to air heated 
 in cold weather ; the dew-point ; 73 per cent of saturation the healthy 
 standard ; statistics in hospitals, Washington and Boston ; shallow vcs-
 
 XVI ANALYSIS OF CONTENTS. 
 
 sels of water on stoves and heating coils or hot-air ducts (p. 30) ; hy- 
 grometers. 
 
 CHAPTER IV. Examination of the Air. Microscopic: Woulfe's bottles 
 of pure distilled water connected by tubes and an air-pump (p. 32) ; cul- 
 tivating solution. Chemical: tests for carbonic dioxide, (pp. 33-37). 
 
 CHAPTER V. Amount of Air required, One person evolves from 0'4 
 to 0'7 of a cubic foot of carbonic dioxide in an hour, and vitiates 2,000 
 to 3,500 cubic feet of air per hour (p. 39) ; a school-room of average size 
 (28 x 34 x 14 feet) would supply fresh air for less than seven minutes if 
 there were no means of ventilation ; how to estimate the amount of air 
 passing through a room (p. 40) ; air rushes into a vacuum with a velocity 
 equal to what a body acquires in falling five miles ; it rushes into a 
 room through a ventilator at a velocity equal to eight times the square root 
 of the height of the exit orifice multiplied by the difference between the 
 out-door and in-door temperatures in degrees Fahr. and divided by 4 91 (p. 
 42) ; the anemometer can measure this ; insufficiency of ventilating 
 registers and flues ordinarily in use (p. 44) ; air should be distributed to 
 all parts of room through many registers. 
 
 CHAPTER VI. General Principles of Ventilation. Natural ventilation 
 secured through the tendency of heated air to rise ; artificial ventilation 
 secured by mechanical power illustration (p. 47). 
 
 CHAPTER VII. Natural Ventilation. Ventilators should be at the 
 top of the room (p. 48) ; foul air rises with the heated air and is not to 
 be found at the bottom of the room ; Mr. Leeds's experiment not conclu- 
 sive (p. 60). 
 
 CHAPTER VIII. Inlets. Should be placed near the floor ; but avoid 
 cold drafts ; warm the air before admitting it to the room ; downward 
 currents in summer; the inlets for air for 75 children should have an 
 area of 10 square feet, and there should be the same area to the outlet 
 flues, where there is a good aspirating chimney giving a velocity of 7'7 
 feet per second ; the inlets should always be distributed round the room, 
 so that free diffusion may occur ; the air furnished from a pure source 
 and drawn from some distance above the ground (p. 54) ; shapes of cowls 
 or conical caps to the shafts ; shafts frequently cleaned (p. 56). 
 
 CHAPTER IX. Regulating the Draft of Openings the Wind. The ac- 
 tion of the wind modifies the results obtained : increases the pressure of 
 the air on the windward side of the room ; measurement of its amount 
 (p. 57) ; classification of winds ; Dr. Arnott's current-regulating air-valve 
 (p. 58) ; admission of air at the top of the room ; McKinnell's circular 
 tube (p. 61).
 
 ANALYSIS OF CONTENTS. xvii 
 
 CHAPTER X. Ventilation by Windows. Primary office of windows to 
 admit light ; secondary office to ventilate ; the best ventilators in sum- 
 mer ; admit dust and smoke ; deflection of currents admitted by means 
 of oblique boards fastened to the sash (p. 64) ; method of opening win- 
 dows when the wind is blowing in order to secure fresh air without drafts 
 (p. 66) ; the best results secured by double windows (p. 68). 
 
 CHAPTER XI. Artificial Ventilation. The vacuum movement aspi- 
 rating chimneys ; a column of heated air moves up the chimney and sucks 
 up the foul air from the school-room through a register ; English House 
 of Commons uses aspirating chimneys ; pure air drawn down one chim- 
 ney and foul air drawn up another (p. 72); Montgolfier's formula for 
 calculating the velocity of an upward current in a chimney (p. 74) ; ob- 
 jection to carrying down the foul-air tubes to the furnace (p. 75) ; neces- 
 sity of tall chimneys for ventilating ; efficiency of jets of steam in mov- 
 ing air (p. 76) ; " absolute temperature " ; the distance above " absolute 
 zero " which is 459'4 Fahr. ; best to combine ventilating-flue with the 
 smoke-chimney. 
 
 CHAPTER XII. Movement of the Air by Mechanical Means. Vacuum 
 movement ; place in the foul-air duct an extracting fan or blower (p. 79) ; 
 or let the blower force the fresh air into the room, a better method be- 
 cause it fills the room with pure air, whereas the exhaust fan draws out 
 the air from the room, but does not regulate the quality of the inflowing 
 air ; hence impure air may come in through windows and doors as well as 
 fresh air ; the " plenum movement " forces the fresh air into the room, 
 the propeller being placed in the inlet duct ; the air forced into the room 
 perflation, blowing through can be regulated perfectly in all cli- 
 mates (p. 80) ; the plenum movement by far the best method of ven- 
 tilating. 
 
 CHAPTER XIII. Air-PropeUers. Revolving fans used for the most 
 part ; Dr. Arnott's ventilating propeller (p. 83) ; Rittenger's fan (p. 84) ; 
 Comb's fan (p. 87) ; Blackman's fan as modified by Hope Brothers ; pat- 
 ent of Hendry and others (p. 88). 
 
 CHAPTER XIV. Expense of the Plenum Movement. Table of tem- 
 peratures ; number of months that fire is required in twenty-eight cities (p. 
 91) ; a thermal unit, the amount of heat required to raise the temperature 
 of one pound of water 1 will raise 48 cubic feet of air 1" (p. 92) ; 180,000 
 feet required in one hour in a school-room of 60 pupils ; hence, to raise 
 that temperature 35, the average amount for Chicago, 131,250 thermal 
 units per hour are required ; the loss of heat through the walls exposed 
 to external air, for 4 walls, 7,937 thermal units per hour (p. 93) ; loss
 
 ANALYSIS OF CONTENTS. 
 
 through 6 windows, 3,572 thermal units, making total loss per hour, for 
 fresh air and walls, 142,759 thermal units, requiring 18 pounds of coal per 
 hour ; for seven months, a 10-room building would cost $512, if coal ia 
 $5 per ton (p. 94) ; this about the actual average cost of fuel in buildings 
 that do not secure ventilation, but use the same air 30 to 60 minutes 
 (p. 95) ; the heat is ordinarily wasted by windows, doors, too small heat- 
 ing-surfaces, and the failure to introduce warm air at different points 
 in the room (p. 96). 
 
 CHAPTER XV. Cost of Ventilating Apparatus. Cost of Aspirating 
 Chimney (p. 97) ; to secure a velocity of 8 feet per second for the air in 
 the chimney requires 21 pounds of coal per hour, which is 3 pounds 
 more than is required to heat the room, making the aspirating chimney 
 expensive unless heated by the smoke-stack (p. 99); diagram of aspi- 
 rating chimney heated by smoke-stack (p. 100) ; such chimneys usually 
 made too small ; should furnish at least 6 square feet of sectional area 
 for each room, and for 14 rooms be 9 feet square (p. 101); cost of the 
 plenum movement (p. 1 02) ; the Rittenger fan requires one horse-power 
 for each room, and 5 to 8 pounds of coal per hour ; the Blackman fan 
 and the Hope water-motor fan much cheaper (p. 102); advantages of 
 plenum movement acts in all weathers and establishes current of fresh 
 air independent of windows or accidental openings (p. 103). 
 
 CHAPTER XVI. Warming. Temperature of the room should be 70' 
 for school-rooms (p. 104) ; with sluggish circulation of blood, a person 
 needs a higher temperature; transmission of heat by conduction, con- 
 vection, and radiation (p. 105) ; heaters should be large, so as to avoid 
 overheating of surface ; poisonous gases escape from a red-hot stove ; 
 stoves, steam-pipes, and stove-pipes heat by conduction ; an open fire in 
 a grate heats by radiation ; radiant heat the healthiest (p. 106) ; spec- 
 trum analysis (p. 107) ; sanitary effects of radiant heat it warms the 
 body without heating the air (p. 108) ; but warms only one side at a time 
 (109) ; convection is the method of conveying heat by the movement of 
 currents of warm air (p. 110). 
 
 CHAPTER XVII. Methods of Warming. The open fireplace in the 
 City of London High-School (p. Ill) ; Dr. Arnott's smokeless grate (112); 
 description of it (p. 113); would use 4 pounds of coal per hour for a 
 school-room 30 x 30 x 14 feet ; Boyd's open fireplace provides for ad- 
 mission of cold fresh air and warming it (p. 1 14) ; if stoves are used, 
 large ones should be selected, so as to avoid overheating, and should be 
 lined with fire-brick long smoke-pipe, extending round the room, so as 
 to economize the heat (p. 116); stoves the cheapest means of warming
 
 ANALYSIS OF CONTENTS. x ix 
 
 known; Dr. Arnott's self -regulating stove (p. 117); smoke consumed by 
 it ; common stove with a drum (p. 119) ; improved stoves by A. M. Hicks 
 and A. Dishman, of Kentucky ; Baltimore Heater (p. 120) ; the Ruttan 
 system discussed ; Smead's invention for mixing hot and cold fresh air 
 (p. 122) ; escape of foul air at the bottom of the room in the Ruttan sys- 
 tem (p. 125) ; necessity of strong draft to secure proper ventilation by 
 this system; waste of heat in the top of room (p. 126); necessity of 
 cleansing foul-air passages ; mistakes or neglect of builders. 
 
 CHAPTER XVIII. Steam-Heating. English House of Commons heated 
 by means of furnace- warmed air, on a modified plan of Dr. Reid (p. 129) ; 
 hot-air chamber beneath the floor, foul-air flues at the top of the room ; 
 amount of heat conveyed by steam ; experiment to prove the ratio of 
 latent heat in water to sensible heat (p. 132) ; upon condensation, all the 
 latent heat of steam becomes sensible heat ; Mr. Holly's method of in- 
 sulating steam-pipes ; 1,600 feet of 3-inch pipe lost by radiation only 2 
 per cent (p. 134) ; one pound of coal converts 9 pounds of water into 
 steam, and realizes 8,640 thermal units ; hence 16*66 pounds of coal 
 necessary to supply a room for an hour, being 2 pounds less than by 
 furnace heat (p. 136); direct radiation by steam-coils condemned, unless 
 ventilation is provided ; plan of room with proper ventilation (p. 138) ; 
 Washington school-buildings heated by direct radiation and without ven- 
 tilation (p. 139); steam-pipes extending round the sides of the room 
 near the floor (p. 140) ; heating of same air over and over ; indirect ra- 
 diation by steam-coils placed beneath the floor, and fresh air warmed by 
 passing over them and into the school-room ; needs a good aspirating 
 chimney or a ventilating fan ; steam radiators placed under windows, in 
 order to counteract cold currents, or near the inside walls of the room, to 
 save loss of heat (p. 143); but the heat ascends to the top of the room, 
 and is not distributed properly. 
 
 CHAPTEB XIX. Ideal Plan for Warming and Ventilating. The feet 
 should be kept warmer than the head (p. 145) ; plan described for warm- 
 ing and distributing fresh air through the floor (p. 146) ; 'chimney 8 feet 
 square, with foul-air flues opening into it from the tops of rooms ; fresh- 
 air shaft bringing down the air from the top of the building ; registers 
 along the aisles by the side of the desks (p. 148); method of cleansing 
 the registers (p. 150) ; method of creating a draft in warm weather 
 (p. 152) ; three pipes to regulate the amount of heat supplied (p. 153) ; 
 double joists in the floor necessary for this plan ; sufficient ventilation 
 without resort to the windows ; plan of 16-room school-house, two stories 
 in height (p. 156) ; chimneys placed between the rooms ; iron ladders inside
 
 XX ANALYSIS OF CONTENTS. 
 
 the chimneys (p. 157) ; one half size for 8-room building ; plan for a 6- 
 or 12-room building (p. 158). 
 
 APPENDIX. 
 
 A. Mr. Glaisher's observations on dry- and wet-bulb thermometers ; 
 his factors for testing the moisture of the air (p. 161). 
 
 B. Simple form of aspirating chimney (p. 164) ; formulae for calcu- 
 lating its efficiency. 
 
 C. Formula? for constructing Rittenger's fan (see pp. 84-87). 
 
 D. Conducting powers of materials ; copper more than twice the con- 
 ducting power of iron and zinc, and nearly five times that of lead ; 19 
 times as great conducting power as marble ; 100 times that of brick ; 
 300 times that of oak. 
 
 E. Radiating and absorbing power of bodies ; silver lowest and oil 
 highest (p. 168). 
 
 F. The Blackman fan with author's improvements ; drawings show- 
 ing formation of the blades (p. 170) ; description of devices to prevent 
 back-flow of air (p. 171).
 
 PREFACE. 
 
 THE following pages are not intended to " fill a long- 
 felt want." The greatest necessities are often not felt 
 as wants. If an individual suffers from a cause which 
 is unknown to him, he feels no want, necessarily, to re- 
 move that cause. If a man sickens from a want of pure 
 air, without knowing the cause of his ailment, he never 
 longs for a more salubrious atmosphere as a cure. 
 
 I am fully convinced that people are prematurely 
 dying by thousands simply from a lack of correct and 
 positive convictions concerning impure air ; for, when 
 the true nature of a danger is fully appreciated, the 
 requisite means to avert it will generally be found. 
 
 Every teacher, or other person who works in a viti- 
 ated atmosphere, has doubtless noticed the peculiarly ex- 
 hilarating effect of going into the open air after a day's 
 indoor confinement. My own experience in this respect 
 is so marked that I seldom step from a crowded room 
 into the open air without reflecting on the nature of that 
 invisible cause which made possible a change so sudden 
 and so marked. This reflection is always followed by 
 the mental query : Can not this great difference between 
 the qualities of outdoor and indoor air be remedied?
 
 PREFACE. 
 
 This experience, together with almost daily observation 
 of the attempts of builders to ventilate houses, wherein 
 the simplest physical laws are commonly ignored, has 
 led to the writing of these pages. 
 
 The work is confined to the consideration of school- 
 buildings for three reasons : 1. I am better acquainted 
 with the needs and present condition of school-houses 
 than of any other class of buildings. 2. These build- 
 ings, because of crowded occupancy during successive 
 days, are most in need of perfect ventilation. 3. 
 Knowledge of the correct principles of school-house 
 ventilation is knowledge equally applicable to all build- 
 ings, as the same principles underly all. 
 
 Correct theories and their successful application to 
 the arts of life can not be conceived and executed in 
 a day. Our knowledge of warming and ventilating 
 is a growth to which each generation has probably in 
 some measure contributed. Any contribution, there- 
 fore, to be of value, must be made in the full light of 
 what has preceded it. In preparation for the present 
 task, therefore, I have carefully read the writings of 
 the following authors who have contributed to this sub- 
 ject : Parkes, de Chaumont, Ritchie, Hood, Morin, Ed- 
 wards, Eassie, Reid, Arnott, Tomlinson, Billings, Galton, 
 Leeds, Schumann, Baldwin, Draper, and Lincoln. I 
 also procured from the United States Patent Office 
 drawings and specifications of thirty -different ventilat- 
 ing appliances which have from time to time been pa- 
 tented. Whatever the Bureau of Education has fur- 
 nished has also been read. The best, therefore, that has 
 been thought or done on this subject has been carefully 
 studied, and whatever is valuable has become assimi-
 
 PREFACE. 
 
 lated into this work, in so far as it informed, invigorated, 
 and corrected my own thought. 
 
 The chapter on window-ventilation will, I think, be 
 useful to teachers. While windows at best can furnish 
 only partial and imperfect ventilation, it is only by their 
 skillful management that even so much may be real- 
 ized from them. 
 
 The discussion in this book of some of the modern 
 systems of warming and ventilating is made from an in- 
 dependent and unbiased study of their merits, and with- 
 out any interest in advertising either their excellences 
 or their defects. 
 
 The ideal plan described and illustrated in the last 
 chapter was not conceived until nearly all preceding it 
 had been written. It may be regarded, therefore, as the 
 result of a long and exclusive application to the subject. 
 
 For valuable suggestions, I wish to acknowledge my 
 obligations to Prof. Wm. Jones, Professor of Chemistry 
 in the Kansas City Medical College, for reading the 
 manuscripts on the chemical examination of the air ; to 
 Prof. L. Wiener, of the Kansas City High School, for 
 reading the mathematical discussion of ventilating 
 fans ; and to Prof. J. M. Greenwood, Superintendent 
 of Kansas City Schools, for reading the same and other 
 portions of the manuscripts. 
 
 G. B. MOBKISON. 
 
 Kansas City, Mo.

 
 VENTILATION AND WARMING OF 
 SCHOOL-BUILDINGS. 
 
 CHAPTER I. 
 
 NEEDED INFORMATION. 
 
 ADVICE regarding "fresh air" has not been lacking 
 in amount. Even the most ignorant have some indefinite 
 notion that there is such a thing as "bad air," and that 
 it is not good to breathe it. Teachers of hygiene pro- 
 claim to pupils the virtues of pure air, shut up in school- 
 houses where it is impossible to get it. Physicians 
 advise their patients to take fresh air, and this by going 
 out of doors, thus tacitly realizing that it can not be 
 found indoors. Preachers in churches, where deadly 
 gases from the lungs and poisonous organic emanations 
 from the skin are imprisoned from week to week, em- 
 phasize the importance of properly preserving the physi- 
 cal body. There is a universal recognition that it is bad 
 to breathe impure air ; there is an ignorance no less uni- 
 versal of the conditions of how to avoid it. "When the 
 nature and composition of a deadly drug are known and 
 marked "Poison, "it is properly avoided. In the next 
 section we shall see that much of the air we breathe 
 should be labeled with skull and cross-bones. 
 
 Where is the impure air ? What makes it impure? 
 8
 
 12 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 What are the nature and amount of the impurities ? 
 These are important questions which, among the edu- 
 cated, are tolerably well known. But when these im- 
 purities exist in an occupied room, how are they to be 
 eliminated and replaced by pure air of the proper tem- 
 perature ? These are questions which are no less im- 
 portant ; but they are questions which are seldom an- 
 swered. How to know where impurities exist ; how to 
 expel them as fast as formed, and supply their place 
 with the pure, life-giving element, is a problem second 
 in usefulness to none other. Of the difficulty of the 
 problem we have ample evidence in the fact that it has 
 been but partially solved, and in general practice almost 
 wholly ignored. True, we hear men talk of " good 
 ventilation" and "poor ventilation," but how little this 
 generally means we hope, at least partially, to show in 
 the pages of this little book. 
 
 Of the lack of definite information on this all-impor- 
 tant subject we have abundant evidence. We often hear 
 the questions: "What is the best way to ventilate a 
 school-room ? Whore should the foul air escape ? Where 
 should the pure air be admitted?" These questions, 
 among the first to be met in ventilation, show that even 
 the first principles of matter and its properties are not 
 commonly applied to the gas we call air. 
 
 The school-houses throughout the United States, while 
 they are elegant, tasteful, and costly, are in the main de- 
 ficient in their sanitary requirement of warming and ven- 
 tilating. Whoever may be disposed to doubt the truth 
 of this statement has but to visit the nearest school-house. 
 Probably in nine tenths of all the school-houses in this 
 country ventilation has been ignored altogether, leaving 
 that important function to be performed by the doors 
 and windows. But ventilation should be independent of
 
 NEEDED INFORMATION. 13 
 
 doors and windows, which are primarily intended for 
 other purposes. How many school -rooms in the land 
 could maintain a school with doors and windows made 
 air-tight ? Probably very few, and in the majority suffo- 
 cation would result in less than thirty minutes ! It is a 
 sad travesty on our school architecture that we owe our 
 lives to the mistakes of carpentry, which mistakes arc 
 usually sufficiently ample to supply, in a crude, unwhole- 
 some, and unsatisfactory way, the deficiencies of direct 
 ventilation. 
 
 This want of sufficient and definite information re- 
 garding the ventilation of school-houses is not peculiar to 
 any locality ; it is wide-spread and general. Even the 
 District of Columbia, which is under the direct control 
 of the Central Government, experiences the embarrass- 
 ments which this all-important but vexed problem pre- 
 sents. By a resolution of the House of Representatives, 
 dated February 20, 1882, a commission was appointed for 
 the purpose of investigating the public-school buildings 
 of the District of Columbia. A few quotations from the 
 report of this committee will be to the point : " The 
 principal defect, from a sanitary point of view, in all these 
 buildings is in regard to the fresh-air supply, which is en- 
 tirely insufficient. The method adopted for this purpose 
 is to admit the air through a perforated plate placed be- 
 neath the sills of four windows in each room. Having 
 passed through this plate, the air is supposed to pass 
 downward through a narrow slit in or behind the wall, 
 and to enter the room at a level with the floor and then 
 pass up through a steam radiator which is placed against 
 the window. The sum of the clear opening in the exter- 
 nal plate of each window is from twenty-two to twenty- 
 five square inches, so that the area of clear opening for 
 the supply of pure air to the room is from eighty-eight to
 
 14 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 one hundred square inches, giving an average of about 
 two thirds of one square foot. When it is remembered 
 that this is intended to supply fresh air for sixty children, 
 each of whom should have as a minimum thirty cubic 
 feet of air -per minute, it will be seen that it is simply im- 
 possible to obtain such a supply through the openings 
 provided, which in fact will hardly furnish five cubic feet 
 per minute per pupil. " 
 
 This report has not been quoted from to show the best 
 that has been done in school-house ventilation, but rather 
 what may be considered a fair representation of the aver- 
 age state of affairs throughout the country. 
 
 Something toward a rational system of warming and 
 ventilating is said to have been accomplished at the Bos- 
 ton High School ; also at Denver, in this country ; but 
 more especially at the City of London High School, and 
 the High School of Vienna, in Europe. 
 
 When first contemplating the preparation of this vol- 
 ume, I thought to write to several superintendents, in 
 cities having a reputation for good school-houses, asking 
 them to furnish me with descriptions of their system of 
 heating and ventilating, that I might use them as a feat- 
 ure of my work, incorporating them as models of the best 
 modern types of school-house architecture. Some an- 
 swered by sending a pamphlet in which ventilation is bare- 
 ly referred to ; others by letter ; but the average signifi- 
 cance of them all may be given in the exact words of 
 one of them : " Our high school is a showy building on 
 the outside, but it is not well warmed and ventilated." 
 
 Few things are more needed than a systematic dissemi- 
 nation of the best that is known of proper methods of ven- 
 tilation, as well as stimuli to investigate the underlying 
 principles. A subject so vital to the health and safety of 
 the growing generation should be investigated by every
 
 NEEDED INFORMATION. 15 
 
 teacher of physics, and the known laws of fluid pressure 
 and motion be directly applied and taught. It should be 
 a theme for the educated physician, whose duty it is not 
 only to cure disease but to prevent it. It should be the 
 duty of every school-house architect not only to make the 
 best practical use of the best that is known on the sub- 
 ject, but to furnish annual reports of the conditions of 
 the school-buildings, a description of each building, the 
 cost, method of warming and ventilating, the air-space 
 for each pupil, the percentage of heat which is utilized 
 in the consumption of fuel, etc. The people's right to 
 information on any subject should be measured by the 
 value and indispensableness of the information ; and 
 surely nothing is of more universal importance than the 
 air we breathe, affecting as it does our health, life, and 
 future condition. 
 
 The .importance of this kind of information has not 
 been wholly ignored. The Denver report of 1883 con- 
 tains a chapter on school architecture in which the stu- 
 dious labors of the architect, Mr. Kobert S. Eoeschlaub, 
 are laid down for the consideration and enlightenment of 
 the public. Many valuable hints on the general subject 
 of warming and ventilating have been given by different 
 writers on hygiene, among whom may be mentioned Pro- 
 fessors Parkes and Draper. From a purely scientific stand- 
 point probably the most has been done by Dr. de Chau- 
 mont. The governments of France and England have 
 contributed much knowledge on the subject by health 
 commissions appointed to investigate the sanitary condi- 
 tions of barracks occupied by soldiers ; the reports of 
 General Moran being especially valuable. But it is to 
 Dr. Neil Arnott, the famous Scotch educator and physi- 
 cian, that humanity owes most for practical knowledge 
 on warming and ventilating. Deeply versed in physics,
 
 16 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 being the author of a valuable text-book on that sub- 
 ject, he understood the principles and laws under- 
 lying the subject. A physician, being one of the most 
 eminent in the realm, he well understood the vitiating 
 effects of impure air. A practical inventor, he put his 
 theories in practice by inventing many heating and venti- 
 lating appliances, among which may be mentioned the 
 Arnott stove, the smokeless grate, and an automatic 
 valve for admitting fresh air to fire-places. A philan- 
 thropist, he gave his thoughts and inventions to the 
 world free of charge, -refraining always from securing 
 patents and copyrights. He did not overlook the needs 
 of the schools; he applied his principles to the "Field 
 Lane. Bagged School " by a method to be noticed here- 
 after with excellent results. 
 
 A little reflection will answer why a teacher should 
 undertake to contribute to this important subject. The 
 heaviest blows in any cause have always been struck in 
 self-defense. The teacher is defending himself in en- 
 deavoring to better the atmospheric condition of the 
 school-room where he spends the most of his active life. 
 Whatever may be said in the defense of children who are 
 submitted to the contaminating influences of an impure 
 atmosphere, the same may be urged with tenfold em- 
 phasis in the defense of teachers ; for while the pupil's 
 school life lasts only a few years, the teacher's term is a 
 life-time. While it is the duty and desire of all good 
 men to help others, the sternest e'fforts are always made 
 in the direction of self-preservation, which, if successful, 
 will increase the capacity to help others. I offer no 
 apology, therefore, for contributing to a subject in which 
 all humanity, and especially all teachers, are so deeply 
 interested.
 
 THE EFFECTS OF BKEATEING IMPURE AIR. 17 
 
 CHAPTEK II. 
 
 THE EFFECTS OF BREATHING IMPURE AIR. 
 
 NONE except he who has given special study to the 
 facts begins to realize the injurious effects of breath- 
 ing impure air. Every one knows that a disagreeable 
 feeling accompanies the breathing of impure air ; that a 
 feeling of stupor; inactivity, drowsiness, and sometimes 
 nausea, headache, and vertigo, result directly from the 
 occupancy of ill-ventilated rooms. These sensations are 
 temporary, and are experienced only while the cause is 
 active, and usually the only thought is to temporarily 
 relieve the inconvenience by a recess or a break for fresh 
 air. Seldom do persons reflect on the ulterior effects of 
 these violations of Nature's laws, and when the outer 
 air is reached, and long draughts of the pure element 
 relieve the depressed sensations, and send the invigorat- 
 ing oxygenated life-blood current coursing through the 
 system, raising the spirits and clearing the brain, their 
 reflection usually end with relief, and, when more or less 
 resuscitated and rescued from the fatal stupor (I use the 
 phrase advisedly), the unsuspecting victims crawl back 
 into their "Black Holes," again to fill the system with 
 gaseous poisons, thinking of it only as an unpleasant 
 duty, the immediate endurance of which will bring sub- 
 sequent freedom and relief. But this is a great mistake ; 
 the temporary suffering consequent on the act of breath- 
 ing vitiated air is but a small part of the objection to 
 be urged against it. The principal charge against the 
 breathing of impure air is that it sows the seeds of dis- 
 ease and death, the length of time in which the subject 
 will succumb being in proportion to his strength and 
 power of endurance.
 
 18 VENTILATING AND WARMING OF SCHOOL-BUILDINGS. 
 
 No subject has been more carefully and intelligently 
 studied than the direct and ultimate effects of impure air 
 on the human system, and on no subject is there more 
 unanimity of competent opinion. Besides the general 
 debilitating and weakening effects, which render the sys- 
 tem susceptible to infectious diseases, breathing impure 
 air is believed by the best authorities to be a direct 
 cause of phthisis (consumption) and its accompanying 
 diseases catarrh, bronchitis, pneumonia, and many oth- 
 ers. 
 
 The individual effects of breathing separately the 
 foreign gases usually found in the atmosphere need not 
 be considered here, but it is their combined effect, com- 
 bining as they do with organic emanations from the skin 
 and lungs, that chiefly concerns us in considering the 
 effect of impure air made so by respiration. Carbon- 
 ic dioxide, C0 2 , is commonly considered the poisonous 
 substance in the atmosphere ; this is in the main untrue, 
 for moderately large quantities, when pure and mixed 
 with air, can be breathed with impunity. C0 2 , by its 
 inability to support life, will produce asphyxia by shut- 
 ting out the needed oxygen, but it can not be regarded 
 as a poison. Substantially the same conclusions have 
 been reached by Demarquay, Angus Smith, W. Miiller, 
 Eulenberg, and Hirt, all of whom have made close in- 
 vestigations. It is when mixed with the organic emana- 
 tions from the skin and lungs that the poisonous quality 
 seems to be present ; and Gavarret and Hammond found 
 that the organic matter when taken alone is "highly 
 poisonous." It seems, therefore, that the principal poi- 
 soning agents in impure air are organic. Nevertheless, 
 the amount of C0 8 in the air is highly important, for its 
 presence is a very good index of the amount of the organic 
 impurities, and to measure the percentage of C0 2 is indi-
 
 THE EFFECTS OF BREATHING IMPURE AIR. 19 
 
 rectly to measure the degree of vitiation of the air. (See 
 Examination of the Air.) 
 
 On the disease-producing effects of air rendered im- 
 pure by respiration we have a host of authorities. The 
 following statistics are from the English sanitary record, 
 given by Ransom, showing the comparative death-rate 
 from pulmonary diseases in different localities where the 
 relative impurities are known to vary in about the same 
 ratio as is shown in the death-rate. For all England, 
 1865-'76, 3-54 ; for Salford, 5 -12 ; Manchester, 7 '7 ; West- 
 moreland, one of the healthiest counties, 2 '27; North 
 Wales, 2 '51. It is, of course, not to be forgotten that other 
 causes, such as intemperance, insufficient and improper 
 food, sedentary pursuits, etc., also conspire in these unfa- 
 vorable localities to produce the final result. " But," as 
 Dr. Parkes remarks, "allowing the fullest effect to all 
 other agencies, there is no doubt that the breathing of the 
 vitiated atmosphere of respiration has a most injurious 
 effect on the health." Consumption is commonly attrib- 
 uted to sudden and undue exposure to wet and cold, want 
 of sufficient food, clothing, etc., but Baudelocque says that 
 " impure air is the great cause of consumption, and that 
 hereditary predisposition, un cleanliness, want of clothing, 
 bad food, cold and humid air, are by themselves non- 
 effective." The following paragraph from Parkes's "Hy- 
 giene " I copy for the weight of authority in the eminent 
 names mentioned therein : 
 
 " Carmichael, in his work on 'Scrofula' (1810), gives 
 some most striking instances where impure air, bad diet, 
 and deficient exercise concurred together to produce a 
 most formidable mortality from phthisis. In one in- 
 stance in the Dublin House of Industry, where scrofula 
 was formerly so common as to be thought contagious, 
 there were in one ward, sixty feet long by eighteen feet
 
 20 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 wide, thirty-eight beds, each containing four children ; 
 the atmosphere was so bad that in the morning the air of 
 the ward was unendurable. In some of the schools exam- 
 ined by Carmichael the diet was excellent, and the only 
 causes for the excessive phthisis were the foul air and the 
 want of exercise. This was the case also in the house and 
 school examined by Neil Arnott in 1832. Lepelletier 
 also records some good evidence. Prof. Alison, of Edin- 
 burgh, and Sir James Clark, in his invaluable work, lay 
 great stress on it. Neil Arnott, Toynbee, Guy, and others, 
 brought forward some striking examples before the Health 
 of Towns Commission. Dr. Henry MacCormac has in- 
 sisted with great cogency on this mode of origin of phthi- 
 sis ; and Dr. Greenhow also enumerates this cause as oc- 
 cupying a prominent place." 
 
 Gavin Milroy, in his pamphlet on the " Health of the 
 Royal Navy," expresses his belief that the extraordinary 
 mortality from consumption on some of the ships was due 
 mainly to improper ventilation. The writer on the sub- 
 ject of "Consumption" in " Chambers' s Encyclopaedia" 
 says: "Among the determining causes of consumption 
 in large populations the best ascertained are those con- 
 nected with overcrowding and bad ventilation." Lan- 
 genbeck, an eminent anatomist, says that the prime cause 
 of consumption is breathing impure air. 
 
 Impure air is also believed by the best authorities to 
 be one of the principal causes of epidemics. Dr. Carpen- 
 ter, than whom there is no abler authority, says : "It is 
 impossible for any one who carefully examines the evi- 
 dence to hesitate for a moment in the conclusion that the 
 fatality of epidemics is almost invariably in precise pro- 
 portion to the degree in which an impure atmosphere has 
 been habitually respired." The Board of Health of New 
 York conclude that forty per cent of all deaths are caused
 
 TIIE EFFECTS OF BREATHING IMPrRE AIR. 21 
 
 by breathing impure air. In view of such alarming facts, 
 this same board declares: "Viewing the causes of pre- 
 ventable diseases, and their fatal results, we unhesitatingly 
 state that the first sanitary want in New York and Brook- 
 lyn is ventilation." Direct experiment described in an- 
 other place, no less than the direct evidence of the senses, 
 proves that the air in our school-rooms is impure in al- 
 most all cases, and in a majority of them to a degree far 
 beyond the danger line. 
 
 In view of these facts, and the results as proved by 
 the authorities above cited, why is it regarded by the 
 public with such indifference ? When a school-house is 
 blown down by a hurricane, killing and maiming a score 
 of children, it is justly regarded as a great calamity ; a 
 vacation is given to quiet the excited fears of parents and 
 children ; investigating committees are appointed to lo- 
 cate the responsibility, and the faces of the whole pop- 
 ulace are blanched with apprehension. Why is this? 
 Why does the intelligent parent send his child to a 
 school-room pcorly ventilated and crowded with chil- 
 dren, some of whom are breathing into a stagnant air 
 the germs of disease and death, while others, from un- 
 washed bodies, are delivering into it their deadly ema- 
 nations, and all without a protest on the part of those 
 even who provide proper hygienic conditions at home ? 
 It is because the effects of the one are immediate, occupy 
 little time, the number killed can be actually counted, 
 and the exact magnitude of the calamity estimated all at 
 once. In the other case the process is slower, but of far 
 greater extent ; the actual results are by the general pub- 
 lic less definitely known, and custom and attention to 
 other matters divert the attention, and the deadly de- 
 struction of the innocents by impure air goes on silently, 
 constantly, and powerfully. While noisy demonstrations
 
 22 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 like that of the cyclone attract attention, and inspire fear 
 and terror, it is in the silent forces that the danger lies. 
 Nature's most destructive forces, as well as her strongest 
 constructive ones, are silent in their operations ; but when 
 Science detects a silent, insidious enemy to human welfare, 
 it is not only our duty to assume an attitude of self-defense 
 and self-protection, but it should be regarded as folly 
 not to do so. Could the real effects of breathing impure 
 air be fully realized by the public, and the actual amount 
 that is really breathed be definitely known, such a knowl- 
 edge would constitute a most powerful stimulus toward 
 solving the problem of ventilation, as well as create a dis- 
 position to provide the means necessary thereto. 
 
 The effects of breathing impure air thus far consid- 
 ered are pathological, but it has its pedagogical and eco- 
 nomical aspects. Every observing teacher knows the 
 immediate relation between the vitiated air in the school- 
 room and the work he wishes the pupils to perform. 
 Much of the disappointment of poor lessons and the tend- 
 ency to disorder are due directly to this cause. The 
 brain unsupplied with a proper amount of pure blood re- 
 fuses to act, and the will is powerless to arouse the flag- 
 ging energies ; the general feeling of discomfort, dissatis- 
 faction, and unrest which always accompanies a bad state 
 of the blood breeds most of the school-room squabbles, 
 antagonism, misunderstanding, and dislike which are 
 wont to occur between teacher and pupil. The pupil 
 apparently at variance with his teacher is really at war 
 with his own feelings, caused by an impure and stagnated 
 condition of the blood. The teacher who sometimes 
 thinks the pupils are all conspiring against him, and who, 
 with dizzy and clouded brain, says the wrong thing at 
 the wrong time, is really struggling with the poison which, 
 on account of his long seclusion from the cheerful air, has
 
 TI1E EFFECTS OF BREATHING IMPURE AIR. 23 
 
 taken possession of him. Teachers observe how much 
 more satisfactory is the work of the first hour of the day 
 than that of any subsequent hour ; this is not because of 
 weariness of the pupils., it is because they are made stupid 
 and obtuse, and the teachers made uneasy and fretful, by 
 the accumulating poisons from skin and lungs. 
 
 From an economical standpoint it would, of course, 
 be impossible to estimate the financial waste of breathing 
 impure air, but it can not but be enormous. In a com- 
 fortable atmosphere of proper temperature and purity 
 as much mental labor can be accomplished in one hour 
 as can be accomplished in six in an atmosphere rendered 
 impure by respiration. This is, of course, but a random 
 estimate, but I am quite sure that whatever of error it 
 contains is on the side of underestimating the deteriorat- 
 ing influences of impure air rather than of overestimating 
 the value of pure air. If, then, we suppose perfect ven- 
 tilation possible, and that this estimate is not overdrawn, 
 the conclusion follows that in those school-rooms where 
 ventilation is imperfect and the air impure six sevenths 
 of the money expended to educate a child is wasted. 
 Doubtless this will appear to some as an exaggerated 
 statement ; but, if we accept the premises (and this will 
 readily be done by all who have tried to think in an un- 
 ventilatcd room), the conclusion is inevitable. This con- 
 clusion supposes that perfect ventilation costs no more 
 than imperfect or no ventilation ; while this is not strictly 
 true, tho difference is insignificant when compared with 
 the loss we are considering. In any discussion of the 
 feasibility of incurring the additional expense of the most 
 perfect ventilation, this loss occasioned by the want of 
 such ventilation must not be ignored.
 
 24 VENTILATION AND WARMING OF SCUOOL-BUILDINGS. 
 
 CHAPTER III. 
 
 THE AIR. 
 
 TJie Composition of the Air. The gaseous envelope 
 which surrounds the earth, and which we call air, is one 
 of the conditions of animal and plant existence. It is 
 evident, therefore, that a definite knowledge of its com- 
 position and properties is all important. In order to in- 
 vestigate the abnormal conditions which often prevail, 
 with a view to correcting them, we must first know the 
 normal conditions. 
 
 The air is composed mainly of two gases, oxygen and 
 nitrogen, in the proportion of about 21 of the former to 
 79 of the latter. The following, from Parkes's " Hygiene," 
 is probably as exact as has yet been ascertained : 
 
 Oxygen 209-6 per 1,000 volumes. 
 
 Nitrogen 790-0 " " " 
 
 Carbonic dioxide (C0 2 ) '4 " " " 
 
 Watery vapor Varies with the temperature. 
 
 Ammonia Trace. 
 
 Organic matter 
 
 Ozone. . 
 
 Salts of sodium Variable. 
 
 Other mineral substances. 
 
 Pure air is usually considered as consisting exclusively 
 of oxygen and nitrogen, all other elements existing as 
 impurities in it. But as the air is a mixture of the 
 constituents, and not a chemical compound, and as the 
 proportion of these elements is variable, it seems more 
 reasonable to regard as the true normal air that propor- 
 tion of the different elements which best conserves the 
 ordinary uses of air in the support of plant and animal 
 life. Without the C0 2 , small though it be, the air would
 
 THE AIR. 25 
 
 be wanting in that constituent which plants most need ; 
 and a certain amount of watery vapor is equally indis- 
 pensable for the use of animals. It seems, therefore, that 
 C0 3 and watery vapor, in the proportions above men- 
 tioned,* are really as truly constituents of air as oxygen 
 and nitrogen. 
 
 Impurities in the Air. There are many substances, in 
 many forms and from various sources, constantly passing 
 into the air, tending to make it impure and unfit for 
 respiration. Of these, those which more especially con- 
 cern us in consideration of the condition of our school- 
 houses are vapors and gases from the skin and lungs, 
 principally C0 2 and vapor of water ; solid particles of 
 scaly epithelium from the skin, fibers of cotton, wool, 
 etc., bits of hair, wood, coal, chalk-dust, and many other 
 things which have a tendency to enter the blood through 
 the delicate air-cells in the lungs, if gaseous, and to lodge 
 in the air-passages or be drawn into the lungs if solid, 
 there to irritate by their presence, and poison the system 
 by their decay. 
 
 But Nature, when not hampered by man, has provided 
 a compensation for this poisoning process by a counter 
 process of purification. The winds scatter the impurities, 
 diluting them with large quantities of air, oxidizing them 
 into simple compounds, and rendering them harmless. 
 The tendency which gases have to diffuse causes poison- 
 ous substances to be rapidly diluted, to such a degree as 
 to destroy their destructive power. It is evident, then, 
 that wherever the contaminating process is active there 
 also should the purifying process be active. Wherever 
 an unusual amount of unwholesome matter is being 
 
 * The exact amount of watery vapor in the air which best serves the 
 purposes of respiration is not definitely known, but, as far as ascertained, 
 it is considered to be about seventy per cent of saturation. 
 2
 
 26 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 evolved, there especially should the purifying conditions 
 be present ; air in such places, to remain pure, must be 
 changed in rapid succession, in order that dilution, diffu- 
 sion, and oxidation may fulfill their legitimate functions. 
 In a school-room the contaminating process can not but 
 be rapid, and wherever ample provision is not made for 
 rapidly changing the air of the room a dangerous con- 
 dition of affairs is sure to exist. 
 
 In addition to the inorganic substance suspended in 
 the air there is a vast number of organized bodies. While 
 some of these organisms are to be found in pure air, they 
 are vastly more numerous in impure air, and more espe- 
 cially in that impure air made so by animals. Ammonia 
 seems to be the great supporter of the countless hosts, so 
 much so that the amount of this gas found present in the 
 air at any time and place is thought to be a fair indication 
 of the relative number of organisms there present. More 
 than two hundred distinct forms of microscopic animals 
 have been discovered in the atmosphere* (Ehrenburg). 
 The precise effect of these organisms on health is not 
 known, but it is generally believed the effect is detri- 
 mental. Bacteria of many forms, and spores of fungi, 
 are also found in the air, and all these organisms are 
 known to thrive in the organic impurities found in the 
 air. Painstaking investigations as to the disease-producing 
 power of these organisms have been in progress within 
 the past few years by Drs. Koch and Pasteur, and while 
 it is generally believed that these organisms and certain 
 diseases are related as cause and effect, no definite germ 
 theory of disease has yet (1886) been accepted by the 
 medical profession. The facts that are known, how- 
 
 * The presence of organic matter in the air may be shown by the 
 aeroscope, or by forcing air through strong sulphuric acid, when, if pres- 
 ent, the organic matter will turn the acid dark.
 
 TEE AIR. 27 
 
 ever, and in which we are here interested are : That a 
 large number of impurities exist in the air that these 
 impurities congregate in inclosed, unventilated spaces 
 where they are produced, and that they have a detriment- 
 al influence on the health. 
 
 The external air from which the school-room must be 
 supplied has impurities peculiar to itself and to the lo- 
 cality whence obtained. Dust and smoke exist in the air 
 in large quantities, as well as the products of decaying or- 
 ganic matter from the surface of the earth. Equal quan- 
 tities of these impurities are not found in all parts of the 
 air. Dust and smoke, owing to their tendency to settle, 
 will be found in larger quantities nearest the earth. In 
 a series of analyses on street-dust, at different elevations, 
 Tichborne found that the amount of dust was not only 
 inversely proportional to the elevation, but that the per- 
 centage of organic matter that it contained decreases with 
 the elevation ; street-dust near the ground containing 45 '2 
 per cent of organic matter, and that at the top of a pillar 
 134 feet high only 29 '7 per cent. The same must be true 
 as to the relative quantity of organic impurities at different 
 elevations. Gases rising from decaying matter on the 
 earth must rise a certain distance before they can come 
 into contact with sufficient pure air to dilute and diffuse 
 them. The reason why "ground-air" is unwholesome 
 is thus seen to be evident. The importance of these facts 
 will appear when we come to consider the source of the 
 fresh- air supply in ventilation. 
 
 There are other sources of impurities, not to be over- 
 looked, always existing in rooms heated by stoves or by 
 the direct radiation of steam-pipes. The most serious of 
 these is found in the use of stoves, which give off, when 
 hot, a poisonous gas. The blue flame sometimes noticed 
 in stoves, when coal is first put in, is due to the burning
 
 28 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 of carbonic monoxide CO a very poisonous gas. Iron, 
 when moderately hot, is not pervious to this gas, which 
 then passes harmlessly up the chimney ; but, when 
 strongly heated, iron loses the power of retaining it, be- 
 comes pervious, and allows the poisonous gas to escape 
 into the room. 
 
 Another source of impurity, which is common both 
 to stoves and to steam-pipes, where the latter are exposed, 
 is in the burning and charring of small particles of or- 
 ganic matter which settle on them. This burning is 
 known to have a very injurious effect on the breathing 
 qualities of air in a room, and should be remembered 
 when considering the choice of the method of heating. 
 
 Humidity of the Air. The quantity of watery vapor 
 found in the air varies with the locality, temperature, 
 and various local conditions, and is important from a 
 sanitary point of view. The right proportion of moist- 
 ure in the air constitutes one of the conditions of a 
 healthy climate. In the heating and ventilating of build- 
 ings, where the proper proportion of watery vapor is 
 found not to be present, it may be supplied by artificial 
 means. A knowledge, therefore, of the proper condi- 
 tions of humidity, as well as a knowledge of the means of 
 supplying them when absent, is thus seen to be impor- 
 tant. 
 
 In crowded school-rooms the symptoms of fainting 
 often evinced by pupils is thought to be partly or wholly 
 due to an insufficient amount of moisture in the air of 
 the room. Other physiological symptoms of an atmos- 
 phere too dry are parched lips and tongue, a dry, fever- 
 ish condition of the skin, and, in those children predis- 
 posed to lung diseases, a hacking cough, resulting from 
 the desiccating effect of excessively dry air on the lungs 
 and bronchial tubes.
 
 THE AIR. 29 
 
 The drying power of air depends not so much upon 
 the actual quantity of moisture already in the air, as 
 upon the capacity of the air, under certain conditions, to 
 receive more ; these conditions being mainly the varia- 
 tions of temperature. If the air of a room containing a 
 certain amount of moisture be raised in temperature sev- 
 eral degrees, its capacity for more moisture may be much 
 increased, while the actual amount already present may 
 not be materially diminished. Hot air expands, and is 
 thereby rendered thirsty, greedily extracting water from 
 everything moist with which it comes in contact. Air at 
 any temperature, when it contains as much vapor of water 
 as it can hold without depositing it in the form of dew, 
 fog, etc., is said to be saturated, but it is plain that air 
 which is saturated at one temperature will cease to be so 
 at a higher temperature unless more moisture be added. 
 This point of saturation is called the dew-point. The 
 dew-point the temperature at which the vapor in the 
 air condenses is, therefore, variable, and always depend- 
 ent on the amount of vapor of water in the air. The 
 dew-point is taken as the standard in estimating the hu- 
 midity of the air, and is taken as 100 per cent. 
 
 The sanitary condition of the air, as influenced by 
 humidity, has not received the attention that its im- 
 portance demands, yet enough has been done to enable us 
 to estimate within limits fairly narrow. Dr. do Chau- 
 mont, in some experiments in various rooms containing 
 air of standard respiratory purity, found that the average 
 humidity is 73 per cent of saturation. This, it must be 
 remembered, was taken in England, where the climate is 
 much more moist than that of America. Probably an 
 humidity somewhat less would answer for our climate, but 
 in any case a given standard must be regarded as only 
 provisional, changing with the temperature of the room
 
 30 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 at the time of testing ; 63 Fahr. was the temperature used 
 in the experiments of de Chaumont. 
 
 Some observations have been made in this country by 
 D. L. Huntington at the Barnes Hospital, Washington, 
 and by Dr. Cowles at the Boston City Hospital. The 
 results are as follows : " First week in December, 1877. 
 Average external temperature 38^ ; average temperature 
 of the wards, from 71 to 76 Fahr. Average relative 
 humidity, from 44 to 49 per cent of saturation ; of outer 
 air, 74." This, it will be noticed, shows a much lower 
 per cent of moisture in the room than that given by the 
 English standard, yet it was claimed that notwithstand- 
 ing this small quantity "a peculiar feeling of freshness 
 and purity was perceived by those who entered the room." 
 
 This "peculiar feeling" which is always experienced 
 in passing into a warm room in winter is, I think, hard- 
 ly a trustworthy teat of the atmospheric purity ; and it 
 seems further unreasonable to suppose that the best sani- 
 tary conditions would admit so great a difference as 74 
 and 44 per cent between the outer and inner air. This 
 opinion will be further strengthened if we accept the 
 statement of Dr. Parkes, that " warmth and great hu- 
 midity are borne on the whole more easily than cold and 
 great humidity." There is little doubt that some differ- 
 ence exists in the amount of atmospheric moisture re- 
 quired by different individuals, but arrangement should 
 always be made to suit the average needs of the majority. 
 From what I have been able to learn from study and ob- 
 servation, I believe that 70 to 75 per cent may safely be 
 taken as a provisional standard of humidity for the air 
 of school-rooms. 
 
 In rooms where the air is too dry, it may be moistened 
 in winter by placing shallow vessels of .water on stoves, 
 on heating coils of steam or hot-water pipes, or in the
 
 EXAMINATION OF THE AIR. 31 
 
 hot-air ducts. In summer, moistening by artificial means 
 will seldom be required, but when, on account of unusual 
 dry ness of season, the conditions so require, it may be done 
 by sprinkling floors (not a very advisable method), or by 
 ejecting cold water in spray through a series of small holes. 
 The humidity of the air may be determined directly 
 by means of an hygrometer, or indirectly by means of wet 
 and dry bulb thermometers. In most hygrometers a bright 
 surface is cooled till dew is deposited thereon, and the 
 temperature then noted. Owing to the sensitiveness of 
 hair to changes in humidity, it is sometimes made use of 
 as an hygrometer ; hair shortens in dry and lengthens in 
 moist air ; and if a hair be fastened by one end to an in- 
 flexible support and the other end attached to one end 
 of a needle hung on a pivot, the other end of the needle 
 moving over a graduated scale, it will form a tolerably 
 accurate measure of humidity. The method used by me 
 is that of the wet and dry bulb thermometer with Glai- 
 sher's factors. (See Appendix A.) 
 
 CHAPTER IV. 
 
 EXAMINATION OF THE AIR. 
 
 Microscopic. The microscopic examination of bodies 
 suspended in the air is rapidly growing in importance. 
 While the work may still be regarded as in its infancy, 
 much has been done by Koch, Pasteur, and others, to- 
 ward determining the effect on the health of organic 
 microscopic bodies in the air. 
 
 It is, of course, not to be expected of one who is 
 merely testing the respirability of the air in a school-
 
 32 VENTILATION AND WARMIN6 OF SCHOOL-BUILDINGS. 
 
 room to search for specific disease-producing germs ; but as 
 large quantities of dust, smoke, etc., suspended in the air, 
 tend to make it irrespirable in proportion to the amount 
 of these impurities existing therein, a knowledge of the 
 relative quantity of suspended matter, as well as the nature 
 of it, becomes a necessary part of the work of testing the 
 fitness of air for respiration. A fair knowledge of the 
 respirable quality can be obtained without microscopic 
 tests ; but as these observations are otherwise interesting 
 and instructive, I here describe the method used by me, 
 which is only one of the many now in use by microscopists. 
 
 Arrange a series of Woulfe's bottles containing pure 
 distilled water, connected by tubes, and pass through this 
 the air to be examined. The air in passing through the 
 water leaves its suspended particles in the water, a drop 
 of which can be examined under the microscope. If the 
 water was pure distilled, all matter found in it in the 
 experiment came from the air.* 
 
 As a means of passing the air through the water, an 
 air-pump or aspirator may be used. I use an air-pump 
 which is so constructed as to admit the easy attachment 
 of a small tube. The cubical capacity of the cylinder 
 being known, the amount of air drawn through the water 
 may be found by multiplying the capacity of the cylinder 
 by the number of strokes. Should such a pump not be 
 accessible, an aspirator may be made by taking a tin vessel 
 of known capacity, with an opening at the top to receive 
 the tube, and a tap below to let out the water. Fill this 
 with water, attach the tube and open the tap ; as the 
 water runs down, the vessel will be filled with air drawn 
 through the water. 
 
 * It is not, as some suppose, a 'native characteristic of water to con- 
 tain " live things." Pure water is absolutely devoid of everything except 
 its two constituent elements, oxygen and hydrogen.
 
 EXAMINATION OF THE AIR. 33 
 
 The nature of the organisms in the air can be further 
 studied, if desired, by passing the air through a cultivat- 
 ing solution, which is set aside and the germs carefully 
 studied from day to day as they develop. A solution of 
 isinglass, two parts in 400 parts of pure distilled water 
 (Fodor), makes a good medium. 
 
 Chemical. A complete analysis of impure air compre- 
 hends the quantitative and qualitative tests for carbonic 
 dioxide, C0 2 , free ammonia, NH 3 , and other nitrogenous 
 matter, oxidizable matters, nitrous and nitric acids, and 
 hydrogen sulphide, H 2 S ; but for ordinary practical pur- 
 poses the determination of the C0 2 is by far the most 
 important, and is ordinarily the only one which need be 
 made. While the poisonous qualities of the air are not 
 wholly due to the presence of the C0 2 per se, the amount 
 of this gas found to be present is, in air made impure by 
 respiration, generally a good measure for other impurities 
 to which the poisonous quality is principally due. Owing 
 to this fact, a careful test for the amount of C0 2 contained 
 in a given atmosphere is generally the only one which 
 need be made where air is tested merely to determine its 
 respiratory purity. 
 
 The mere presence of C0 2 in the air may be tested by 
 exposing baryta-water in a shallow 9pen dish ; if C0 2 is 
 present, a white deposit of barium carbonate will be formed 
 on the surface of the liquid, the amount and rapidity of 
 the formation being proportional to the amount of C0 2 in 
 the air. The exact proportion of C0 2 in a given quantity 
 of air may be determined by different processes ; but that 
 of Pettenkofer, which is familiar to me by use, is probably 
 as good as any. Briefly it is as follows : Take a glass bot- 
 tle of about one gallon capacity 4 litres ; fill the bottle 
 with water in the place where the air is to be tested. 
 Pour out the water, allowing it to drain. This expels the
 
 34 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 air formerly in the bottle, and fills it with the air of the 
 room. Now pour into the bottle 60 c. c. (cubic centime- 
 tres) of clear lime- or baryta- water ; close the mouth air- 
 tight, and shake. Allow this to stand eight hours if lime- 
 water, or one hour if baryta-water. The C0 2 will all be 
 absorbed by the water, the causticity of which will be 
 lessened in proportion to the quantity of C0 2 in the 
 vessel ; the C0 2 , being acid, neutralizing the lime by 
 forming a neutral carbonate. If now the causticity of 
 the water be known before and after the C0 2 has been 
 united with it, the difference will show the amount of' 
 lime which has united with C0 2 . To find the causticity 
 of lime, prepare an oxalic-acid solution.* Take 30 c. c. of 
 fresh lime-water, like that used in the first part of the 
 experiment, and mix with it just enough of the oxalic 
 solution to exactly neutralize it.f The amount of the 
 oxalic solution which will be required to do this will be 
 somewhere between 34 and 41 milligrammes, the amount 
 varying with the temperature. Now take 30 c. c. of the 
 solution in the large bottle, after the expiration of the 
 prescribed time, and try how much of the oxalic solution 
 it takes exactly to neutralize it. The difference between 
 this and the preceding shows the number of milligrammes 
 of lime which were united with the C0 2 contained in the 
 air in the bottle. Multiply this difference by 4 795,J 
 
 * This solution is prepared by dissolving 2'25 grammes of crystallized 
 oxalic acid in one litre of pure distilled water ; 1 c. c. neutralizes 1 milli- 
 gramme of lime. 
 
 f It will be neutralized when it does not change the color of turmeric 
 paper dipped into it. 
 
 The molecular weight of CaO (lime) is 56, and that of C0 3 , 44, the 
 weight of C0 a being therefore - that of lime. The ratio between weight 
 and volume at 32 Fahr. is -506. Then $ x -506 x 2 = '795, the factor 
 used above. The reason for multiplying by 2 will be evident by remember- 
 ing that only 30 c. c. of the lime-water was used out of the 60 c. c. put in.
 
 EXAMINATION OF THE AIR. 35 
 
 which gives the number of c. c. of C0 2 contained in the 
 air examined. Find the amount of air in the bottle by 
 subtracting the volume of the lime-water put in, 60 c. c., 
 from the total capacity of the bottle expressed in litres. 
 The c.c. of C0 2 divided by the volume of air will give the 
 number of c. c. of C0 2 in 1,000 parts of air. The follow- 
 ing general formula will be found useful in solving ex- 
 fa a') 0-795 _, 
 amples : x = - ^-3 . Reference: z=c. c. of C0 2 per 
 
 litre ; a = first alkalinity of lime-water ; a'= alkalinity 
 after exposure to air in the jar ; c capacity of the jar ; 
 d = space occupied by the lime-water. When the air is 
 several degrees either below or above the freezing point, as 
 will generally be the case, a correction for temperature must 
 be made, as a given volume of air when expanded by heat 
 is less dense, and when contracted by cold more dense, 
 than normal. " Air expands or contracts '2 per cent for 
 every degree it deviates from the standard " ; hence -2 
 per cent added to the result for every degree above 32 
 Fahr., or subtracted for every degree below 32 Fahr., 
 will be a sufficient correction for temperature. At ordina- 
 ry elevations a correction for pressure will not be necessary. 
 The following example, selected from a series of ex- 
 periments made by me, will be sufficient to illustrate the 
 process. By first testing the alkalinity of the lime-water 
 =38 ; after exposure a'=30 ; c=4,500 c. c., d 60 c. c. 
 
 fQQ HC\\ fi'^CK 
 
 rru lOO'^QUI V t V<J _, .,.,-. f /-Nyv -, r\r\r\ 1 
 
 Then x ^ . ,. . =1-432 c.c. of C0 2 per 1,000 vol- 
 4,50060 
 
 umes of air. Correcting for temperature, which was in 
 this instance 80, or 48 above 32: 48 X '002+lXl '432= 
 1-569. As there are only -4 c. c. C0 3 in air of standard 
 purity, the above test shows a bad condition of air. 
 
 Prof. William Jones proposes the following modifica- 
 tion of this method, which will give the sa.me results, 
 5
 
 36 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 lessening somewhat the work of calculation where a large 
 number of tests are made. If we take the molecular 
 weights of C0 3 and H 2 C 2 4 -f~ 2H 2 (oxalic acid), which 
 are 43*89, and 125 "7 respectively, we see that one part by 
 
 125 '7 
 weight of C0 3 is equal to , or 2 '8639 by weight of 
 
 ~Lo oJ 
 
 H 2 C 2 4 + 2H 2 ; and as one part by weight of C0 2 is 
 equal to 0*5086 part by volume, then each 2 -8639 parts of 
 oxalic acid are equal to 0*5086 part by volume of carbonic 
 acid. Therefore 0-5086 : 28,639 : : 1 : 56,309, or 5-6309 parts 
 by weight of oxalic acid are equal to 1 volume of carbonic 
 acid ; consequently, if we dissolve 5 "63 grains of crystal- 
 lized oxalic acid in 1 litre of distilled water, 1 c. c. of this 
 solution will be equal to 1 c. c. of C0 2 , thus indicating the 
 volume of C0 2 present in a given amount of air by the 
 difference in the number of cubic centimetres of oxalic acid 
 solution required to neutralize a given amount of lime- or 
 baryta-water before and after shaking with the air, with- 
 out any more calculation ; except that if we use only one 
 half the amount of lime-water that has been shaken with 
 the air, it will be necessary to multiply the result by 2. 
 
 In the absence of the means for chemical tests, the 
 sense of smell by a healthy person may be employed with 
 fair results. Dr. de Chaumont states that -4132 parts of 
 C0 2 per 1,000 volumes of air can be barely perceived by 
 the sense of smell carefully exercised. When 0*6708 of a 
 part is present the organic matter becomes disagreeable, 
 and when 0*9054 of a part is present it becomes offensive 
 and oppressive. After this limit has been reached, and 
 the air becomes loaded with still more impurities, the 
 sense of smell becomes unable to detect shades of differ- 
 ence. He concludes, from a long series of such experi- 
 ments, that " 0*2 per 1,000 in round numbers is the maxi- 
 mum of respiratory impurity admissible in a properly
 
 EXAMINATION OF THE AIR. 
 
 37 
 
 ventilated air-space." * It must be remembered that after 
 the first few minutes in the room the sense of smell be- 
 comes unreliable. This test can be applied only by per- 
 sons of keen sense and close and discriminating judg- 
 ment, and then only at the moment of first entrance into 
 the room from pure external air. 
 
 EXPERIMENTAL TESTS. 
 
 No. of examination. . . . 
 
 Time of day at which 
 air was taken ... . . 
 
 1 
 
 2 
 
 3 
 
 4 
 
 11 A. M. 
 
 50 
 8, all open 
 above and 
 below. 
 
 50 
 80 
 68 
 Strong 
 breeze. 
 
 8063 
 1-669 
 
 507 
 Steam 
 direct ra- 
 diation. 
 One outlet, 
 10x16 in., 
 into a shaft 
 without 
 heat. 
 
 2 P.M. 
 
 55 
 6, three of 
 them being 
 open at the 
 bottom. 
 75 
 76 
 72 
 Calm. 
 
 3-387 
 1-923 
 
 513 
 No fire. 
 
 By windows 
 only. 
 
 11 A. If. 
 
 45 
 8, three of 
 them raised 
 from the 
 bottom. 
 60 
 88 
 76 
 Gentle 
 breeze. 
 
 2-155 
 1-642 
 
 493 
 Steam 
 direct ra- 
 diation. 
 One outlet, 
 10x16 in., 
 into a shaft 
 without 
 heat. 
 
 4 P. M. 
 
 51 
 4, on oppo- 
 site sides 
 and all 
 open. 
 70 
 70 
 68 
 Gentle 
 breeze. 
 
 1-055 
 6415 
 
 486 
 No fire. 
 
 No. of pupils in the 
 room 
 
 No. and condition of 
 windows. 
 
 External temperature. . 
 
 ( Above 
 Internal temp. ] Be , ow 
 
 Condition of the wind. 
 
 No. of parts of C0 a in 
 1,000 parts of air 
 taken from near ceil- 
 inf. . 
 
 No. of parts of COj in 
 1,000 parts of air 
 taken from near the 
 floor 
 
 No. of parts of C0 4 in 
 1,000 parts of exter- 
 nal air taken outside 
 the building 
 
 Method of heating. . . . 
 Method of ventilating. 
 
 * Boscoc found in a school of sixty-seven boys 8'1 parts of C0 t per
 
 38 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 The accompanying tabulated record shows the results 
 of a few tests made by me on specimens of air taken from 
 different school-rooms. 
 
 These results show first, that all the rooms from 
 which air was taken contained an amount of C0 3 consid- 
 erably above the limit of respiratory impurity (i. e., *4 + '2 
 = *6 parts in 1,000 parts of air); secondly, that the amount 
 of C0 2 is due not so much to the number of hours the 
 room had been occupied as to the conditions of ventila- 
 tion. In Experiment 4, where the purest air was found, 
 the room had been occupied all day, but on this particu- 
 lar day the weather was fine, with a breeze from the west. 
 The windows were on opposite sides, east and west, so 
 that a current of air was passing directly through the 
 room. On some other day, when the windows might have 
 to be closed on account of bad weather, and the wind 
 happened to blow in some other direction, this room 
 would have no ventilating advantages over the others. 
 Thirdly, that C0 2 was in every case found in the largest 
 quantities at the top of the room ; and, fourthly, that the 
 external air is generally pure, so far as C0 2 is concerned. 
 
 CHAPTEE V. 
 
 AMOUNT OF AIE EEQUIKED. 
 
 "WHEN decided by examination that the air of a school- 
 room is unfit for respiration, the question naturally pre- 
 sents itself, How may this air be renewed, and what should 
 
 1,000. Weaver found in a girls' school in Leicester, England, 5'28 parts 
 per 1,000. Pettenkofer found in an occupied room 7'23 parts per 1,000.
 
 AMOUNT OF AIR REQUIRED. 39 
 
 be the rate of this renewal in order that it may be main- 
 tained in a state of respirable purity ? Let"tis consider 
 the latter question first : The amount of C0 2 evolved by 
 one person in one hour is adult males, 0*7 of a cubic foot ; 
 adult females, 0'6 ; children, 0'4. If we take 0'2 C0 2 
 per 1,000 volumes of air as the extreme admissible limit 
 of vitiation (and this is as much as is safely admissible), 
 the number of cubic feet of fresh air which will be viti- 
 ated by each person in one hour may be expressed by the 
 
 formula v = -r, where v = the required amount of fresh 
 
 air per hour ; a = the amount of C0 2 exhaled by each 
 person, and b = the limit of admissible impurity. In the 
 case of children, where the amount of C0 8 exhaled is 0*4, 
 
 0-4 
 
 we have by substitution - - = 2. 5 in the formula is ex- 
 0'ifi 
 
 pressed per thousand volumes ; therefore v represents the 
 number of thousands of cubic feet of air. 
 
 The number of cubic feet of air vitiated by each child 
 in one hour is 2,000. In high-schools, where pupils are 
 large, it would be more nearly correct to use 0*6 of a 
 cubic foot as the amount of C0 2 evolved by each ; and in 
 colleges 0'7 of a cubic foot, the amount given off by 
 adults. These conditions, then, would require, respect- 
 ively, for small children, 2,000 cubic feet per head ; for 
 high-school pupils, 3,000 cubic feet ; and for college stu- 
 dents, 3,500 cubic feet. In a school-room of ordinary 
 size there are 28 X 34 X 14 = 13,328 cubic feet of air. 
 From the foregoing it was seen that each child requires 
 2,000 cubic feet of pure air per hour ; sixty children 
 about the average school number will therefore require 
 the same amount in one minute. It is plain, then, to see 
 that the air in the average school-room, were there no 
 means for ventilation, would become vitiated in less than
 
 40 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 seven minutes 13,328 -*-2,000 = 6-6.6+ min. It ap- 
 pears evident, then, that in order to meet the require- 
 ments of perfect ventilation the air in the room must be 
 changed every seven minutes, and the total amount of 
 fresh air which must be passed through a school-room of 
 ordinary capacity and occupancy is 2,000 X 60 = 120,000 
 cubic feet per hour. 
 
 After the first few minutes the time required to viti- 
 ate the amount of air the room contains the size of the 
 room makes no difference in the constant amount re- 
 quired. It is the number and size of the occupants which 
 must regulate the amount necessary for ventilation. The 
 size of the room, and the number of cubic feet to be sup- 
 plied each pupil, are important only for the fact that a 
 given amount of air can be passed through a large room 
 without producing strong currents more easily than the 
 same amount through a small room. The size of the 
 room, therefore, and the number of cubic feet per head, 
 are no indications of the respiratory quality of the air 
 therein contained. 
 
 How to Estimate the Amount of Air passing through 
 a Room. The air passing through a room may be esti- 
 mated either by measuring it as it comes in or as it passes 
 out. Before making these measurements they should be 
 made intelligible by an understanding of a few funda- 
 mental properties of fluids, of which air is one. 
 
 All movement in the air is caused by an inequality of 
 pressure in different localities due to inequality of heat. 
 Wind air in motion is simply the movement of the air 
 of one locality toward another locality containing air of 
 less density. As heat expands the air, making it lighter, 
 the movement of the air will always be in the direction 
 of the warmer temperature. The air, being matter, has 
 weight, and is subject to the same laws of pressure and
 
 AMOUNT OF AIR REQUIRED. 41 
 
 falling as other matter. If the atmosphere were of uni- 
 form density from top to bottom, it would form an en- 
 velope around the earth about five miles in depth. 
 
 The velocity which a body acquires in falling is ex- 
 pressed by the formula v = v2gH., where v = velocity, 
 H = height through which the body falls, g = the accel- 
 eration due to gravity. This is nearly equal to eight 
 times the square root of the height, and for simplicity 
 may be so expressed : 8^/H. 
 
 The particles which constitute a fluid, as water or air, 
 have no friction among themselves, and exert pressure in 
 all directions. Another fundamental law following from 
 this is that fluids will pass through an orifice below the 
 surface with the same velocity that a body would acquire 
 in falling a distance equal to that between the surface 
 and the orifice ; and that, when passing through an orifice 
 in a partition separating the fluid from another fluid of 
 different height, the velocity will be equal to that of a 
 body falling a distance equal to the difference of the 
 depth of the fluids on the two sides. The pressure of the 
 air on any surface near the earth is about fifteen pounds 
 to the square inch, and is the weight of a column of air 
 five miles in height. Air, then, would rush into a vacuum 
 with a velocity which a body would acquire in falling five 
 miles. It would rush into a room containing air of a less 
 pressure, which may be considered as a partial vacuum, 
 with a velocity due to a height which represents the dif- 
 ference between outside and inside pressure. Now, a di- 
 rect relation exists in any substance between weight and 
 density, and as a volume of air increases regularly with 
 the temperature, lessening its density and weight in the 
 same ratio, a means for measuring the difference of press- 
 ure by comparing the temperature of the air on either 
 side of the partition is thus afforded ; and this, together
 
 42 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 with a comparison of the relative height of the entrance 
 and exit orifices in a room, enables us to calculate the 
 velocity with which air is passing. 
 
 Air expands -^^ of its volume for every degree Fahr- 
 enheit. The height through which a body would fall 
 having the required velocity which we are considering 
 
 is expressed by the formula H = - - , where II = the 
 
 491 
 
 height through which a body would fall to acquire the 
 velocity under consideration ; h = height from the en- 
 trance to the exit orifice ; t = the difference in tempera- 
 ture between inside and outside. By substituting this 
 value of H in the general formula (v = 8 /v/ H) for falling 
 
 bodies, we have v = 8 1/ .. in feet per second. 
 
 491 
 
 Example : Suppose li = 14 ft., t = 20 ; then v = 
 
 /14 X 20 
 
 8y j = 6 '032 -f- ft., the velocity of the air per sec- 
 ond. An allowance of from one sixth to one half of the 
 theoretical velocity must always be made for friction,* 
 according to circumstances and special peculiarities of the 
 openings and ducts or tubes leading thereto. Having 
 found the velocity, the amount of fresh air may be found 
 by multiplying the velocity by the sum of the areas of 
 the openings expressed in feet. 
 
 These calculations are equally true whether the open- 
 ings are windows or apertures constructed especially for 
 ventilation. When windows are used, a difficulty arises 
 in making the computation, due to the difficulty of ascer- 
 taining where the air enters and where it leaves the room; 
 windows on different sides of the room, being of the same 
 
 * For discussion of particular cases and practical formulas for deter- 
 mining velocity, see Appendix " B."
 
 AMOUNT OF AIR REQUIRED. 43 
 
 distance from the floor, and their openings at different 
 times varying in position and size to suit the freaks of 
 the occupants, are inlets or outlets according to the cir- 
 cumstances. The same window may be inlet and outlet 
 at the same time, producing cross-currents and strong 
 draughts, the disagreeable nature of which is well known 
 to all victims of window-ventilation. 
 
 The simple conditions governing the possibilities of 
 this method of measuring the amount of air which is 
 passing through a room are, that the air in the room 
 must be of a higher temperature than that outside ; the 
 air must pass in from below and pass out above. In sum- 
 mer, when the outside temperature is equal to or higher 
 than that inside, this method is not available. It is also 
 unreliable when the wind is blowing, unless the openings 
 are properly guarded against the unequal pressure due to 
 this cause.* 
 
 The Anemometer. "When the wind is blowing, or any 
 of the conditions of the above method of measuring the 
 velocity of the air are otherwise not complied with, the 
 anemometer must be used. Of these instruments many 
 kinds are now in use, but in principle they are all essen- 
 tially the same. They consist of fans revolving on an 
 axis (after the manner of a wind-mill) which is connected 
 by wheel-work with an indicator showing the velocity of 
 the air which is moving the fans. 
 
 Insufficiency of ordinary Air- Supply. School-houses 
 which make pretensions to ventilation other than by 
 means of doors and windows commonly have a single 
 register for the admission of fresh air, and one for the 
 exit of foul air. These are variously situated some- 
 times at the top of the room, sometimes at the bottom, 
 
 * Sec " Regulating the Drafts of Openings," page 66.
 
 44 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 and at other times midway between floor and ceiling. 
 The proper position for these ventilating openings will be 
 considered in another place ; but, supposing them to be 
 situated properly, we are ready from the foregoing to con- 
 sider the efficiency of these breathing-holes. 
 
 These registers are usually about 16 X 18 inches, and 
 sometimes much smaller ; this gives a total area for the 
 entrance of pure air of 288 square inches, or 2 square feet; 
 multiplying by 6, the number expressing the velocity in 
 the example previously given (where the height of the 
 room is 14 feet, the difference between the temperature 
 of air outside and inside 20), we have 12, the number of 
 cubic feet of air passing into the room per second ; mul- 
 tiplying this by 3,600, we have 43,200, the number of 
 cubic feet of air passing into the room per hour. We saw 
 above that each pupil requires 2,000 cubic feet per hour 
 in order that the degree of vitiation may not exceed the 
 limit, 0*2 of a part of C0 2 per 1,000 parts of air ; and that 
 sixty pupils require 120,000 cubic feet of pure air per 
 hour. It thus becomes evident that this amount of open- 
 ing will ordinarily supply only about one third of the 
 quantity of air required. Air passed through an opening 
 of this size, in order to be sufficient, would have to move 
 at the rate of about eighteen feet per second, or about 
 eight and a half miles per hour. When air is moving 
 two miles per hour, it becomes perceptible to the senses as 
 wind ; and if it were passing into a room at the rate of 
 eight miles an hour it would be a breeze which would be 
 dangerous to the pupils sitting near it, especially if it was 
 not warmed before passing in. This velocity of air would 
 be neither tolerable nor possible, unless it should be first 
 warmed and then forced into the room by means of aspi- 
 rating chimneys, or by mechanical means described in 
 another place.
 
 GENERAL PRINCIPLES OF VENTILATION. 45 
 
 TJie Distribution of Air. No less important than the 
 adequate quantity of air to be supplied to a room is its 
 proper distribution. This is impossible where but a sin- 
 gle opening is furnished for admission, and the same for 
 exit. Under these conditions the air may pass through 
 the room in a narrow current, without being utilized by 
 mixing with the vitiated air of the room. 
 
 In considering these single openings of the ordinary 
 size, I have supposed the conditions such as to make them 
 count for their greatest possible utility ; but when we 
 remember that they are often misplaced that the differ- 
 ence in internal and external temperature is often not so 
 favorable as the case considered; that the passages through 
 which the air must pass before reaching the room, and in 
 making its final escape in leaving it, do by friction greatly 
 lessen the amount given by the theoretical estimate; and 
 that these passages are often neglected and impure we 
 are forced to the conclusion that this much provision for 
 furnishing pure air to a school-room is in its effects, if not 
 absolutely nil, so very little that it may be ignored. The 
 further conclusion is, that what air pupils generally get 
 comes in through windows and doors. 
 
 CHAPTER VI. 
 
 GENERAL PRINCIPLES OF VENTILATION. 
 
 HAVING learned something of the nature and require- 
 ments of the air we breathe, of the source of its impuri- 
 ties, the amount needed, and the way by which it may bo 
 measured, we are ready to consider how a room is to be 
 supplied with air of the requisite quantity and quality,
 
 46 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 and how its proper temperature may be maintained. How 
 to remove the air from a room as fast as it becomes viti- 
 ated, and to supply its place with pure air of the proper 
 temperature, are questions in engineering, to answer which 
 is at once necessary and difficult. 
 
 The difficulties which attend the answering of these 
 questions are in part theoretical and in part mechanical ; 
 theoretical, in that all devices and means to accomplish 
 the ends of ventilation must rest on general principles, 
 and conform to the known laws of matter and motion ; 
 mechanical, in that the successful application of the most 
 obvious general principle implies good workmanship. 
 
 The most perfect theory of ventilation, based on cor- 
 rect physical principles, might be totally defeated in its 
 ends by a bungling carpenter. These important ques- 
 tions, then, can be met and answered only by accurate 
 and skillful workmanship, based on correct theory. 
 
 A secondary difficulty attending all efforts to engineer 
 air is that it is invisible. Could the air and the impuri- 
 ties which it contains be seen, we should at every turn 
 receive practical hints how to move it, as well as constant 
 admonition that it is to our best interests to do so ; but, 
 instead of the advantages which the visibility of the air 
 would afford, we have to rely on our knowledge of its 
 properties and laws, and on our reason in interpreting ex- 
 isting causes and their attendant effects. 
 
 Warming and ventilating are antagonistic processes 
 the one is addition, the other subtraction ; the one a giv- 
 ing, the other a taking away. But, as the two processes 
 are inseparably connected and mutually interdependent, 
 it will be necessary, partially at least, to treat of them 
 together. 
 
 Natural and Artificial Ventilation. So many differ- 
 ent devices of warming and ventilating have been em-
 
 GENERAL PRINCIPLES OF VENTILATION. 47 
 
 ployed, some of which make use of mechanical means 
 to move the air, that ventilation is usually considered 
 under two classes natural and artificial ventilation. 
 
 In natural ventilation the openings are so constructed 
 and arranged as to make the natural forces in the rising 
 of warm air, and in the falling of cold air, do the work of 
 changing the air of the room. 
 
 In artificial ventilation, the air is forced into the room 
 by mechanical power. 
 
 This classification, while convenient enough, is, after 
 all, entirely arbitrary. All ventilation is in one sense 
 artificial, and in another sense all ventilation is natural. 
 "Natural" ventilation is artificial, as it requires art in 
 making the openings of the proper construction and po- 
 sition ; "artificial" ventilation is natural in that natural 
 laws must be utilized and directed. 
 
 Illustration of the General Theory of Ventilation. 
 As the laws of motion and pressure governing fluids are 
 equally applicable to air and to water, the following in- 
 teresting experiment illustrates the general theory ol 
 ventilation : 
 
 Take a large glass jar and fill it with clear water to 
 represent the external atmosphere. Fill a large square 
 bottle, having apertures near the top and bottom, with 
 colored water to represent the internal air of the room 
 and its impurities ; see that it is of the same temperature 
 as the water in the jar, and then suspend the bottle in 
 the water in the jar. On carefully opening the apertures 
 it will be noticed that a mingling of the clear and colored 
 waters takes place very slowly. This is due to diffusion, 
 and illustrates what takes place in the air when the in- 
 ternal and external temperatures are equal and the at- 
 mosphere quiet. If now the colored water be heated to a 
 
 temperature several degrees above that of the clear water, 
 6
 
 48 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 it will be seen to rise and pass out of the upper apertures, 
 the outside clear water, being heavier, flowing in at the 
 lower aperture. The colored water soon passes out, leav- 
 ing the bottle filled with the pure water. This illustrates 
 ventilation in winter, when the air of the room is warmer 
 than that outside. If the colored water in the bottle be 
 cooled by ice or a freezing mixture, and the outside water 
 be warmed, the current will be reversed ; the heavier, 
 cool colored water will flow out at the lower aperture, 
 and the outside clear water will flow in through the upper 
 one to fill the space thus left. This illustrates the action 
 of the air in summer, when the air of the room is cooler 
 than the air outside. 
 
 CHAPTER VII. 
 
 NATUKAL VENTILATION". 
 
 Position of Ventilators. The question is often asked, 
 Where should ventilators be placed ? Some say at the 
 top of the room, others say at the bottom ; the experi- 
 ment described in the foregoing chapter answers this 
 question. When only the conditions of ordinary natural 
 ventilation are present, there can be but one answer 
 ventilators should be at the top of the room. The air in 
 the room, when warmer than the outside air, must come 
 in at the bottom and go out at the top ; and, when cooler 
 than the outside air, must com'e in at the top and pass 
 out at the bottom. 
 
 This movement may be reversed, but it must be done 
 by means other than that afforded by natural ventilation; 
 and, even in the plenum movement described in another
 
 NATURAL VENTILATION. 49 
 
 place, it is always the part of economy to work with Na- 
 ture, and not against her. 
 
 Ventilators are often placed near the floor because of 
 the erroneous idea that the foul air is below. The fact 
 that C0 8 is a little heavier than air has led to the hasty 
 conclusion that it at once settles, and is to be found near 
 the floor. The facts are that C0 3 forms a very small per- 
 centage of each expired breath, and its temperature, as well 
 as that of the air from the lungs with which it is mixed, is 
 when leaving the mouth much higher than that of the sur- 
 rounding air ; it is therefore lighter, and at once rises ; and 
 the tendency it has toward rapid diffusion prevents its sink- 
 ing even after it has become as cool as the air of the room. 
 
 The tendency which gases of great differences of den- 
 sity have to diffuse, even against the force of gravity, may 
 be illustrated by taking two bottles, filled, one with hy- 
 drogen, the lightest gas known, and the other with the 
 heavy C0 2 gas which we are considering. Connect the 
 bottles by a glass tube passing through the cork stoppers 
 of each. Leave them for a time with the light hydrogen 
 above and the heavy C0 2 below, and in a short time they 
 will be thoroughly mixed, the heavy gas having risen 
 against gravity to mix with the hydrogen. 
 
 In certain modern systems of heating and ventilating, 
 to be described hereafter, the ventilating ducts are placed 
 near the floor. This is thought by the inventors of these 
 systems necessary to prevent the too rapid escape of the 
 fresh air as it enters the room and immediately rises to 
 the top. If this warm air were properly distributed as it 
 entered, it would be sufficiently vitiated to require its 
 removal on reaching the top of the room ; but, as this is 
 seldom the case, the difficulty is met by placing the out- 
 lets below, allowing the upper hot air to press the cooler 
 air down and out. 
 
 3
 
 50 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 As a justification for this arrangement, the authors of 
 these systems have tried to persuade themselves and the 
 public that the foul air of a room is at the bottom, and 
 have conducted some curious experiments to prove this ; 
 among which may be mentioned those of Mr. Leeds, of 
 Philadelphia. 
 
 He first takes a large glass tube, with perforated caps 
 at each end, as represented in Fig. 1. Smoke is blown 
 
 FIG. l. 
 
 into the tuhe through the rubber tube T. It will first 
 rise to the top of the tube, but on cooling it soon settles 
 to the bottom and flows out at A. This smoke is intended 
 to represent the carbonic-acid gas, C0 2 , from the lungs, 
 which it is claimed by this experiment will fall like the 
 smoke at a temperature of from 60 to 70. 
 
 This, with no further knowledge of the nature of 
 smoke and C0 2 , would readily pass for a legitimate com- 
 parison ; but a moment's reflection reveals a fallacy. 
 Smoke is solid matter in a fine state of division floating 
 in warm rising air. When the air cools and ceases to" 
 rise, these solid particles by their superior specific gravity 
 fall. But C0 2 is not a solid; it is a gas ; and gases have 
 the property of rapid diffusion. The relatively small 
 quantity of C0 3 at any one time rising with the heated 
 air will have more than time thoroughly to diffuse in the 
 air before the latter cools sufficiently to allow the settling 
 of a similarly suspended solid. 
 
 Another alleged proof, by the same author, consists
 
 INLETS. 51 
 
 of admitting some C0 2 in an undiluted state into an in- 
 closed space in which tapers are burning at different 
 heights. The C0 3 being heavier than air, when thus 
 poured in, of course sinks to the bottom, and extinguishes 
 the lower lights first, which is given as sufficient proof 
 that foul air is found at the bottom of the room. Here 
 the quantity of C0 2 used, and the time given for its dif- 
 fusion, are all out of proportion with the actual con- 
 ditions ever existing in an occupied room. 
 
 Experimental demonstration does not always demon- 
 strate. Nothing may be more misleading in its teaching 
 than an experiment which is only half interpreted. Should 
 this reasoning be thought insufficient, the facts may be 
 easily ascertained by examining the air for C0 2 . (See 
 Experimental Tests, page 37.) 
 
 CHAPTER VIII. 
 
 INLETS. 
 
 Position. Inlets, as before intimated, should be placed 
 near the floor. It is sometimes claimed that in order to 
 avoid cold air on the feet the inlets should be placed seven 
 to nine feet from the floor, so that the cold air on entering 
 may sink and mingle with the warmer air of the room as 
 it descends. Too much can not be said against submitting 
 the occupants of a room to cold drafts of air ; and where 
 the air is allowed to enter without being warmed, or with- 
 out provision being made for its warming as it enters, it 
 'is perhaps less objectionable to admit the air from above ; 
 but, as it should be a settled principle in building school- 
 houses that the air should never enter without some pro-
 
 52 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 vision for its warming, the objection to its admission 
 from below disappears. To admit it from anywhere else 
 is practically to destroy the upward direction of the cur- 
 rent, upon which the regular change of the air of the room 
 mainly depends. 
 
 In summer, when the inside air is sometimes cooler 
 than the outside, the ventilation will be downward, and 
 the inlet and outlet openings at the bottom and top of 
 the rooms respectively will change functions, the air com- 
 ing in at the top and going out at the bottom ; but this 
 is not often the case, especially in school-houses where 
 school is not in session during the hottest weather. 
 
 Total Size and Distribution of Inlets. Inlets should, 
 of course, be of sufficient area to admit the requisite 
 amount of air without requiring so high a velocity as to 
 cause drafts. The total area may be easily approximated 
 
 y 
 by the formula A = ,, where A equals the sectional 
 
 area of the inlet ; V equals the volume of air passing 
 through the inlet per hour ; v' equals the velocity of air 
 in feet per second through the inlet ; 3,600 equals num- 
 ber of seconds per hour. It is generally more convenient 
 to let A represent the number of cubic feet of air required 
 per hour by each pupil, then the amount required for 
 any number of pupils can easily be obtained. The value 
 of V has already been discussed. (See Appendix "B.") 
 Example : 
 
 What will be the total sectional area of inlets required 
 in a room capable of accommodating 75 pupils ? If each 
 pupil requires 3,000 cubic feet per hour, and the velocity 
 with which the air can be admitted is found to be 7 feet 
 
 per second, then A = -, = = "119 square foot = 17 '1 
 o, bOO x 7 
 
 square inches for each pupil. By referring to the exam-
 
 INLETS. 53 
 
 pie in Appendix "B," it will be seen that 7*7 is the ve- 
 locity attained when a good aspirating chimney is used. 
 It often happens in ordinary conditions of natural venti- 
 lation that the velocity is not more than 5 feet per second. 
 
 3,000 
 Using this number m the above problem, A = 6QQ v.r = 
 
 square foot, or 24 square inches. Counting 60 as the 
 number of pupils to be supplied, the total area of inlets 
 will be 60 X 24 = 1,440 square inches. This is equal to 
 one inlet 37 '8 inches square, or 10 square feet. About 
 the same area is required for outlets, making 20 square 
 feet as the total area required for inlets and outlets in an 
 ordinary school-room. 
 
 Distribution of Inlets. The air should never be ad- 
 mitted through a single inlet, but should be so distributed 
 around the room that free diffusion may occur. To pass 
 air into a single opening of a large room, and allow it to 
 pass directly out at another opening, may be likened to a 
 waiter who would feed a company by carrying a quantity 
 of food through a dining-room without stopping to pass 
 it around. One foot square is large enough for one 
 opening. In the example given above we have then ten 
 openings, which should be equally distributed around the 
 room ; the same number of outlets would not be re- 
 quired, though they must be equal in area. 
 
 Source of the Air supplying Inlets. It is an im- 
 portant matter, though often overlooked, that the air 
 which furnishes the supply to inlets should come from 
 a pure source. It is generally understood that the sur- 
 face condition of any locality determines largely the 
 condition of the air which comes in contact with that 
 surface. A wind, if blowing over an icy region, will be 
 cold ; if across a dry and arid region, it will be dry, des- 
 iccating, and parching ; if over a swampy, wet locality,
 
 54: VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 where large quantities of organic matter are in a state of 
 decay, it will be laden with sickening vapors and mala- 
 rial germs. 
 
 In full knowledge of these universally recognized facts, 
 the air which furnishes the inlets is often drawn from 
 near the damp ground, and sometimes from the vicinity 
 of back yards and alleys, where all kinds of filth and ref- 
 use pollute this "fresh supply" before it enters the 
 school-room. 
 
 Unless the school-house is extremely fortunate in its 
 location-site, and at some distance away from all other 
 buildings, the air supply should be drawn at some dis- 
 tance from the ground, by means of upright shafts or 
 tubes of the height determined by the circumstances of 
 each case. Fig. 2 illustrates the movement of the air 
 down the shaft, through the room, and out at the venti- 
 lator. A, downcast tube, with conical-shaped cap in- 
 verted ; B, entrance shaft ; C, upcast cowl, with conical- 
 shaped cap erect ; D, outlets in the ceiling ; E, registers 
 admitting air into the room ; E, room ; W, windows. 
 
 The chief objection to the use of down shafts for the 
 purpose of getting pure air is to be found in the retarda- 
 tion due to the friction. This may be entirely overcome 
 by means of aspirating chimneys, but even when these 
 are absent the friction may be largely compensated for by 
 properly arranging the shape of the shafts and ventila- 
 tors. Reference to Fig. 2 will show how this may be done: 
 the wind striking the inclined surface of the inverted 
 conical cap is deflected downward into the shaft, thus 
 increasing the amount of air entering the room. In the 
 ventilator C, on the other hand, the wind striking against 
 the oppositely inclined surface of the erect conical cap, as 
 well as the flange C' below, is deflected upward, causing 
 an upward draft in the ventilating tube.
 
 INLETS. 
 
 55 
 
 "Lobster-backed" cowls are sometimes used on venti- 
 lators to increase their aspirating power. These revolve 
 
 FIG. 2. 
 
 with the wind, keeping the back to the windward, thus 
 preventing the wind from blowing down the tube ; the
 
 56 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 liability, however, of these cowls to get out of order has 
 led to their disuse. 
 
 All shafts and tubes leading to the room should be so 
 constructed as to reduce friction to a minimum, and ad- 
 mit of frequent cleaning ; they should therefore be lined 
 with some smooth, hard material, and be made accessible 
 to the brush of the janitor. Neglect in this particular is 
 often a considerable source of vitiation. Rough brick and 
 mortar shafts and ducts collect large quantities of dirt 
 and organic matter, which by its decay forms a source of 
 pollution, and, being by their construction inaccessible, 
 their vitiating action is constant. 
 
 CHAPTER IX. 
 
 REGULATING THE DRAFT OF OPENINGS THE WIND. 
 
 WE have discussed in another place the nature and 
 velocity of air passing through inlets and outlets, when 
 caused by the inequality of internal and external temper- 
 ature, and the difference in height between inlets and 
 outlets. But the results thus obtained will nearly always 
 be modified by the action of the wind, which is usually 
 blowing in some degree, and which must be in some man- 
 ner compensated for by properly arranged inlets. 
 
 The action of the wind is to increase the pressure of 
 the air on the windward side of the room, and by the aspi- 
 rating power which a moving air-current has on neigh- 
 boring air to decrease the normal pressure on the leeward 
 side. The extra pressure exerted by the wind may be 
 estimated by first ascertaining the velocity by means of an 
 anemometer (q. v.), squaring and multiplying by *005.
 
 REGULATING THE DRAFT OF OPENINGS. 57 
 
 This is expressed by the empirical formula v s X "005 = P, 
 where v = velocity of the wind, P = pressure iu pounds 
 per square foot, and '005 = a constant. 
 
 When an anemometer is not accessible, a tolerably 
 correct estimate of the wind's pressure may be obtained 
 by Beaufort's classification of winds : 1, faint air; 2, light 
 air ; 3, light breeze ; 4, gentle breeze ; 5, fresh breeze ; 6, 
 gentle gale; 7, moderate gale; 8, brisk gale; 9, fresh gale; 
 10, strong gale; 11, hard gale; 12, storm. In this classi- 
 fication the force of the wind is estimated by the scale 
 to 12, which represents all degrees from a calm to a hur- 
 ricane. In using this, any estimate divided by 2, and 
 the result squared, will approximately represent the wind's 
 pressure in pounds. Example: Suppose a " gentle breeze " 
 is blowing. Referring to the classification above, it is 
 seen that "gentle breeze" is No. 4; then (f) 2 = 4, the 
 number of pounds pressure on one square foot of surface. 
 Again: If a "strong gale "is blowing, then (^) 2 = 25 
 pounds. 
 
 In the absence of an anemometer, the velocities of the 
 different winds above enumerated may be calculated by 
 finding the pressure in each by the method last given, 
 and then substitute this value of P in the first formula, 
 from which then find the value of v. For convenient 
 reference I have made th calculations, which may be 
 considered as simply a popular translation into the com- 
 mon language of terms used in referring to wind : 
 
 1. Faint air, 7 miles per hour. 
 
 2. Light air, 14 " 
 
 3. Light breeze, 21 " " 
 
 4. Gentle breeze, 28 " " 
 
 5. Fresh breeze, 35 " " 
 G. Gentle gale, 42 " " 
 7. Moderate gale, 49 " "
 
 58 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 8. Brisk gale, 56 miles per hour. 
 
 9. Fresh gale, 63 " " 
 
 10. Strong gale, 70 " " 
 
 11. Hard gale, 78 " " 
 
 12. Storm, 85 " " 
 
 If action of the wind is not anticipated and provided 
 for, it will defeat the most carefully laid plans for venti- 
 lation ; but, if properly controlled, it may by its perflat- 
 ing, aspirating, and motive power be made an aid instead 
 of being a hindrance. By its perflating power it may be 
 used in counteracting friction by directing the current 
 downward through entrance shafts, as shown in Fig. 2 A. 
 By its aspirating power it may increase the upward draft 
 of a ventilator chimney by blowing directly across the 
 top, or by being directed upward by means of a deflecting 
 surface (Fig. 2 C). 
 
 When inlets are not preceded by down-shafts, but only 
 by short tubes or ducts coming directly from the outer 
 air, they should be guarded by means of guards or valves, 
 to prevent strong gusts of wind from entering the room, 
 which might otherwise occur. The best possible arrange- 
 ment for this purpose would be a modified form of Dr. 
 Arnott's current-regulating air-valve, which he invented 
 for regulating the draft of closed stoves. A sectional 
 
 FIG. 3. _ 
 
 A 
 
 B I 
 
 diagram of this ingenious device is here represented (Fig. 
 3). The bounding lines H E I K represent the outside
 
 REGULATING THE DRAFT OF OPENINGS. 59 
 
 walls of the tube to be fitted into the inlet duct. The 
 arrows show the direction of the air-current ; A I is the 
 opening of the inner extremity of the box, and D H the 
 opening to the outer extremity. G E represents the edge 
 of a lever-frame balanced across the partition C B. F G 
 is a door attached to the lower extremity of the lever- 
 frame EG. W is a sliding weight on the rod extending 
 from F. The half of the lever-frame shown by the broken 
 line C E is covered by a wire screen, through which the 
 air-current flows in its passage into the room. If the 
 current is strong, it is resisted somewhat by the friction 
 against the wires. This resistance causes the screen end of 
 
 o 
 
 the frame to be depressed, and the opposite end, carrying 
 the door F, to be elevated thus partly closing aperture 
 H D. The size of the opening will thus always be in- 
 versely proportional to the strength of the wind. When 
 out of proper balance, it may be corrected by moving the 
 weight W. v This device is remarkable for its ingenious 
 simplicity, and it is also remarkable that it has never 
 been utilized as a current-regulator in ventilation. 
 
 Various devices have been contrived at the inner ter- 
 minus of inlets for preventing a perceptible draft on the 
 windward side of buildings, among which may be men- 
 tioned the Shirringham valve, which gives the wind a de- 
 flection upward as it enters the room. Other forms have 
 been made by Messrs. Bayle, Weaver, and Ellison. All 
 these, however, must be regarded as so many attempts to 
 correct what ought not to exist. If the velocity of wind 
 is not checked before it reaches the inside of the room, it 
 is then too late to manage it satisfactorily. The wind 
 might be successfully managed, and the air at the same 
 time be freed from many of its suspended impurities, by 
 constructing, outside the building to be supplied, large air 
 receptacles supplying the inlets. These receptacles would 
 7
 
 60 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 serve a purpose in supplying air analogous to that of our 
 large reservoirs in supplying water. The entrance to 
 these receptacles could be guarded by filters for abstract- 
 ing suspended impurities: and the fluctuating air pressure 
 due to the wind could be regulated by automatic valves. 
 
 Admitting Air at the Top. When a room is situated 
 so as to make the admission of the air at the bottom in- 
 convenient, it may be admitted from the top. Fig. 4 
 represents McKinnelPs circular tube, which is probably 
 the best arrangement for this form of ventilation. The 
 heat of the room causes the air to rise and pass out at the 
 inner tube, as indicated by the arrows. The addition of 
 the cowl A would tend to promote the same upward cur- 
 rent. The partial vacuum thus formed will be filled by 
 the outside air flowing in at the large encircling tube, the 
 action of which would be further promoted by the addi- 
 tion of the inverted flange B. The horizontal flange C, 
 at the lower extremity of the inner tube, deflects the in- 
 flowing air along the ceiling, distributing it before it falls 
 to mingle with the warm air of the room. 
 
 This method of admitting the air has some advantages. 
 The cold air, by its contact with the warm air near the 
 ceiling, becomes warm before reaching the occupants of 
 the room. By its admission through a tube encircling 
 the warm inner tube, the inflowing air, if cold, becomes 
 warm by contact. This tube will not always act as an 
 outlet. If the windows are opened, cold air will come in 
 from below, supplying the place of the ascending warm 
 air, which will then pass out at both tubes, making them 
 both outlets. 
 
 The conditions of natural ventilation may be sum- 
 marized briefly : The air of the room, made warm by 
 artificial means, and by the heat of bodies, has a tendency 
 to rise ; that it may pass put as fast as vitiated, this ten-
 
 REGULATING THE DRAFT OF OPENINGS. 
 
 Gl 
 
 dency must not be resisted, but promoted by openings 
 from above into aspirating cowls or chimneys. Fresh air, 
 which supplies the place of the outgoing air, must be so 
 admitted as to facilitate the same movement by utilizing
 
 02 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 its power to push. In order that it may be pure, it must 
 be taken from an elevated source by means of an upright 
 shaft. The regularity of the supply must be regulated 
 by properly constructed valves. 
 
 CHAPTER X. 
 
 VENTILATION BY WINDOWS. 
 
 THE primary office of windows is to admit light ; but 
 owing to a lack of proper provision for the passage of 
 fresh air, they must also serve the secondary office of 
 ventilation. It has already been shown that, where ven- 
 tilators exist, they are usually only nominal, their size, 
 position, and construction making their utility almost 
 wholly imaginary. As windows, then, in school-houses 
 already existing, are our only source of fresh air, and 
 furnish us the only means that we may soon reasonably 
 hope for, it behooves us to make the most of them. 
 Where the means are meager, their skillful manipulation 
 becomes still more a necessity. Generally speaking, win- 
 dows are poor ventilators. On a balmy day in spring, 
 when the sky is clear, the dust having been laid by a 
 light shower, and a gentle zephyr is blowing, all the 
 windows may be raised (or dispensed with entirely), and 
 the air allowed to circulate freely through the room. 
 Under such circumstances, windows are the best pos- 
 sible ventilators, unless it were possible to remove the 
 walls also. To ventilate a room on such a day re- 
 quires little forethought. The common instinct of a 
 school-girl to throw open a window is all the art or phi- 
 losophy which the case requires. But when the bitter
 
 VENTILATION BY WINDOWS. 63 
 
 winds of winter are blowing, or rain or snow is pelting 
 one side of the house, or perhaps clouds of dust and 
 smoke are rolling toward the house, the case is different ; 
 the instinct which throws up a window to escape a stifling 
 atmosphere, throws it down again to escape a worse evil. 
 
 When wind has any of the disagreeable accompani- 
 ments above mentioned, the windows should, when possi- 
 ble, be opened on the leeward side. The aspirating power 
 of the wind has a vacuum-forming tendency on the side 
 opposite its direction ; the air will, therefore, if windows 
 be opened on that side, flow out of the room, and suffi- 
 cient air to supply the vacancy thus made will work its 
 way through cracks and crevices on the windward side. 
 
 It often occurs that windows are all on one or two 
 sides of the room ; we then have our choice between the 
 suffocation of closed windows or braving the elements 
 admitted by open ones. Where the only windows happen 
 to be on the windward side, and the wind must be ad- 
 mitted, it is better to open them at the top. The wind 
 will blow in, forcing some of the impure air out. 
 
 Just where the outlets will be can hardly be guessed. 
 About half of the openings to a room, when there is move- 
 ment of the air through them, must of necessity be out- 
 lets. Where the outlets are will depend upon the posi- 
 tion of the inlets and the freaks of the wind. A single 
 opening will sometimes be both inlet and outlet where 
 shifting cross-currents are irregularly passing. The air 
 which thus enters will in some measure mix with the 
 vitiated air of the room, diluting the exhaled poisons. 
 The air which is forced out will carry with it some of the 
 impurities ; the amount, however, depending on local and 
 changing conditions. This kind of ventilation may be 
 likened to the imperfect blood-circulation in the cold- 
 blooded reptiles, which have a single ventricle for both
 
 64: VENTILATION AND WARMING OF S.CHOOL-BUILDINGS. 
 
 pure and impure blood, which is sent through the system 
 in a mixed state. 
 
 The force of the wind admitted through open single 
 windows may be partially checked by fastening a piece 
 of board to the top sash and extending into the room ob- 
 liquely upward so as to retard its fall on the heads of the 
 pupils. In Fig. 5, a, the arrows show the direction of 
 
 FIG. 6. 
 
 R 
 
 the air deflected upward as it passes into the room, E, by 
 the oblique board, a, attached to the upper sash ; Z>, on the 
 other side, represents a board fitted between the casings on 
 the window-stool, and serves a similar function. 
 
 No set rules can be given as to whether windows should 
 be opened from the top or from the bottom. This will 
 depend entirely upon the circumstances upon whether a 
 window when opened is intended for an outlet or an in- 
 let. This requires close observation on the part of the
 
 VENTILATION BY WINDOWS. 
 
 65 
 
 teacher, as well as careful study and an intelligent under- 
 standing of the existing conditions. When the wind is 
 not blowing, all the windows should be opened, both top 
 and bottom ; the size of the openings being regulated to 
 suit the temperature. In this way the air of the room, if 
 it is warmer than the outside air, will rise and pass out at 
 the top ; the outside air, being heavier, will flow in at the 
 bottom. In summer, when the air of the room is cooler 
 than that on the outside, the current will be reversed. 
 
 When the internal and external temperature is about 
 equal, and when no wind is stirring, the windows should 
 be opened about equally from above and below, and as 
 wide as possible, giving diffusion, the only means for ven- 
 tilation which is under the supposed conditions existing, 
 as much freedom as possible. 
 
 It is when the wind is blowing that the greatest diffi- 
 culty is found in ventilating by windows, but by skillful 
 
 FIG. 6. 
 
 management much more can be done toward establishing 
 a constant current than is generally supposed. The most 
 favorable condition is when windows are on opposite sides 
 of the room. Fig. 6 supposes this case, where a modcr-
 
 66 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 ate wind is blowing from the direction indicated by the 
 large arrows. By opening the window on the windward 
 side at the top, and the one on the leeward side at the 
 bottom, a current is established as indicated by the large 
 inside arrows ; this direction being the resultant of two 
 forces one the horizontal force of the wind, the other 
 the greater specific gravity of the cold air. This current, 
 as it passes through, will have an aspirating power to 
 draw the air of the other parts of the room toward it. 
 This is simply the vacuum-forming tendency which fluids 
 always possess when moving. The small arrows show the 
 direction of the air in the various parts. Now if the win- 
 dow at D be slightly raised, and the one at C slightly 
 lowered, the vacuum-forming tendency within will initi- 
 ate a sufficient current through these openings to supply 
 the vacancy. Admitting the cold air at the top, and let- 
 ting the foul air out below, seems to contradict the natu- 
 ral theory of ventilation as before described ; but it must 
 be remembered that here the force of the wind is utilized 
 instead of the unequal weights of columns of hot and cold 
 air. A further advantage is here realized in the cold air 
 being warmed before it strikes the occupants of the room. 
 
 It more frequently occurs, especially in school-houses 
 containing several rooms, that the only windows are on 
 two adjacent sides. In this case it is generally best to 
 make the principal top openings on the side of the strong- 
 est wind, and the principal bottom openings on the re- 
 maining side. The wind will then after entering be 
 deflected by the opposite wall in the direction of least re- 
 sistance, which will be toward the largest openings on the 
 adjacent side. 
 
 When windows are only on one side of the room, 
 the difficulty is still further increased. In this case it is 
 generally better to make the principal opening at the top,
 
 VENTILATION BY WINDOWS. 
 
 67 
 
 and a smaller one at the bottom. The purpose of this is 
 illustrated by Fig. 7. When the wind is very strong, the 
 upward tendency of the inside air may be counteracted 
 
 Fio. 7. 
 
 by a large opening at a. The air, being thus forced in, 
 will seek the lines of least resistance in escaping. By 
 making a small opening at B it will become an outlet, as 
 it has less to oppose than at a, where the momentum of a 
 large inflowing quantity would be encountered. From the 
 laws of fluid pressure it would at first appear that the 
 tendency of the outside air to enter at B would be as great 
 as at a, and, indeed, even more, owing to the greater 
 depth below the surface; but, when it is remembered that 
 the relative friction which fluids have to overcome in 
 passing through small orifices is so much greater, it is 
 plain that in the case of the present example the relative 
 absence of friction in the larger top opening gives to the 
 wind when passing through a momentum which is suffi- 
 cient to establish the current. If, however, the wind is 
 of only moderate velocity, the current will be likely to set
 
 68 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 the other way will enter at the bottom, and pass out at 
 the top. In this case the size of the openings must be 
 suited to the temperature, the number of pupils in the 
 room, as well as their capacity to bear hardship. 
 
 When the wind is not strong, and the location of in- 
 lets and outlets is not evident, they may generally be 
 found by the aid of a feather fastened to the end of a 
 pointer, which, held in front of an opening, will indicate 
 the direction of the passing current. 
 
 The best possible window ventilation requires the use 
 of double windows. Ideal window ventilation would re- 
 quire double windows on four sides of the room. Such 
 conditions would afford a fair degree of purity. By means 
 of double windows the wind may be admitted or kept out 
 when and where desired. Its force could be broken by 
 
 FIG. 8. 
 
 R 
 
 f f 
 
 v S 
 
 being made to pass perpendicularly between the windows 
 before entering the room. Inlets and outlets could be 
 made at the top or bottom as required by the circum- 
 stances, and the strong drafts unavoidable in single win- 
 dows avoided. Fig. 8 illustrates a single case, which, of
 
 VENTILATION BY WINDOWS. 
 
 69 
 
 course, permits of indefinite modification to suit existing 
 circumstances and changing conditions. Here the air 
 enters at A by the upper outer window being lowered ; 
 descending, it enters the room at B, by the inner lower 
 sash being raised; passing over the heater H, it is warmed 
 before striking the pupils ; rising, it passes through the 
 room, and escapes at C, by both inner and outer windows 
 being lowered. 
 
 Suppose another case, that of a stove situated in the 
 middle of the room. Fig. 9 illustrates an instance where 
 
 FIG. 9. 
 
 a single opening serves both as inlet and outlet. By 
 making large openings at A c and B D, by lowering tho 
 outside windows and raising the inside ones ; and the 
 smaller openings, a and b, by slightly lowering. the inside 
 windows, it is possible to divide the cold and hot air cur- 
 rents, as indicated by the arrows the chief controlling 
 principle here being the unequal weight of hot and cold 
 air. Without multiplying instances, suffice it to say that 
 in window ventilation the place and relative size of open- 
 ings must be conditioned by the direction of the wind, 
 the velocity of the wind, and the position of the heater.
 
 70 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 CHAPTER XI. 
 
 ARTIFICIAL VENTILATION. 
 
 As distinguished from so-called natural ventilation, 
 where the air is changed by means of doors and windows, 
 or other openings, the moving forces being the wind and 
 the unequal weights of hot and cold air, certain additional 
 or artificial means may be used whereby the change of air 
 may be made to take place more rapidly, and the regu- 
 larity of the movement more certain, than is possible in 
 natural ventilation. 
 
 The changes of temperature both in frequency and 
 amount are in this country so marked, and the direction 
 and velocity of the wind so various and fickle, that even 
 the most carefully worked plans for the use of the natural 
 methods above described are attended with constant em- 
 barrassment and partial defeat. 
 
 Something has been done toward an intelligent solu- 
 tion of the all-important problem of how to measure out, 
 warm, and furnish to the occupants of crowded rooms air 
 of the proper quantity and quality; but the subject has 
 not received a tithe of the attention that its merits de- 
 mand. To know exactly how much air is needed by a 
 school, and to furnish it by exact mechanical measure- 
 ment, is not a very severe problem, and is one with which 
 the designers of buildings should be familiar. To meas- 
 ure the amount of water, and estimate its velocity, which 
 is necessary to do a certain amount of work, is a problem 
 of every-day experience with the civil engineer. Now air, 
 no less than water, is matter, and subject to nearly the 
 same laws of weight, motion, and measurement ; and to 
 manipulate it in the manner required by the conditions 
 and necessities of ventilation, providing at the same time
 
 ARTIFICIAL VENTILATIOX. 71 
 
 for its exigencies, is an element in school-house construc- 
 tion plainly possible, and should be recognized as a part 
 of the duty of him who is intrusted with this important 
 function. It is as easy to measure air as to measure any 
 other substance ; and, owing to its extreme mobility, its 
 movement is effected more easily than most other matter. 
 
 The different ways by which this movement may be 
 effected may be conveniently considered under two gen- 
 eral heads the vacuum movement and the plenum move- 
 ment. 
 
 TJie Vacuum Movement Aspirating Chimneys. The 
 act of animal respiration is a pumping or vacuum-forming 
 process. As the respiratory cavity is enlarged by muscu- 
 lar effort, the air rushes in to fill the vacancy thus made. 
 Chimneys which serve the purpose of removing smoke 
 from a fire, or the foul air from a room, are therefore 
 called aspirating, because they imitate in a certain way 
 the breathing out of the internal impurities. 
 
 The vacuum-forming power in chimneys, instead of 
 muscular action, is the expanding power of heat, which 
 lightens the air in the chimney when the outside heavier 
 air pushes it upward. The use of the aspirating chimney 
 is evident. It is plain that if the air of a room has com- 
 munication with a chimney by an opening leading into 
 it where the air is hot, rare, and rising, it will be drawn 
 out and up to the outside air. 
 
 The velocity of the air-currents produced by natural 
 ventilation, described above, can by this means be greatly 
 augmented. The utility of downcast shafts for the pur- 
 pose of securing pure air is in ordinary natural ventilation 
 greatly lessened by the friction which air encounters in 
 passing through them : so much so, indeed, that they 
 sometimes have to be discarded, being, when the friction 
 is in excess of the drawing power, obstructionists instead 
 8
 
 72 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 of promoters to ventilation. By the use of the aspirating 
 chimney this difficulty may be overcome. 
 
 In Fig. 10, the fire on the grate Gr produces an upward 
 current through the chimney D. This draws the air 
 
 FIG. 10. 
 
 from the tube E, into which the foul air of the room flows, 
 through the openings/. The partial vacuum thus formed 
 in the room causes the air to flow down the shaft B. The 
 downward and upward cast cowls, a and c, described 
 above, aid further in facilitating the movement. The
 
 ARTIFICIAL VENTILATION. 73 
 
 figure is only intended to illustrate the principle. The 
 details must, of course, be modified in each case to suit 
 circumstances, without violating any of the laws which 
 give to the aspirating chimney its main value. 
 
 The main principles which the figure illustrates are : 
 the air is taken from an elevated source, it is admitted 
 below, and is distributed around the room. It rises and 
 passes out naturally at the top of the room into the par- 
 tial vacuum made in the chimney by the heat from the 
 fire at Gr. The tube E is sometimes carried down to the 
 base of the chimney before entering it ; the object of this 
 being to prevent the reflux of smoke sometimes resulting 
 from sudden changes of conditions, as the wind, rapid 
 lowering of the temperature, etc., producing a temporary 
 reversal of the current down the chimney. This may be 
 effectually prevented by adjusting at the aperture H a 
 valve v opening toward the chimney. This, when unin- 
 fluenced by currents, should hang naturally, closing the 
 aperture by its own weight, yielding readily to a slight 
 pressure of a current from the direction of the room, and 
 closing effectually against a pressure from an opposite 
 current, thus shutting off the smoke resulting from down 
 draught. This method of removing the foul air was first 
 put in successful practice by Dr. Reid in his class-room in 
 Edinburgh. The English House of Commons is venti- 
 lated on the same principle. 
 
 There are other advantages in carrying the foul-air 
 tube directly into the chimney instead of carrying it down- 
 ward. The friction resulting from lengthening the tube, 
 and the inclusion of two more elbows, would materially 
 lessen the draught; furthermore, it has been proved by ex- 
 periment that the draught in a chimney is greatest near the 
 top, directly under the roof. This may be due partly to 
 the increased velocity of the hot air in the chimney near 
 
 4
 
 74 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 the top, caused by an upward acceleration acquired in 
 rising, and partly to diminished resistance to the air as 
 it nears its point of release from the confining walls of 
 the chimney. 
 
 It may at first appear contrary to known laws that the 
 velocity of a rising column of air should be accelerating, 
 but a moment's consideration will be sufficient to under- 
 stand the paradox. Acceleration will always occur when 
 a body free to move is acted upon by a constant sufficient, 
 as the action of gravity on falling bodies. 
 
 The space passed over in unit time, taken at any period 
 of a body's movement, will be measured by the initial 
 velocity due to the constant, plus the velocity previously 
 acquired. Now, a body which has a tendency to rise will 
 accelerate so long as the tendency is constant. Thus, a 
 cork, or other light body, in rising from a great depth in 
 water, would have a greater velocity when near the surface 
 than when it first began to rise. The cause of its rise 
 is the difference between the pressures on its upper and 
 lower surfaces, but as this difference is always the same, 
 whether at a great depth or near the surface, it is a con- 
 stant which augments at every instant the velocity already 
 attained. 
 
 Montgolfier's formula, v = \/%gh, is, under the sup- 
 posed conditions, as true of rising as of falling bodies 
 remembering that g, instead of being 32 feet, now repre- 
 sents the distance the body would rise the first second. 
 This would, of course, depend on the specific gravity of 
 the substance, and would need be determined experiment- 
 ally. The case of the air in the chimney is a little differ- 
 ent from the one supposed, unless it be that the source of 
 the heat be equally distributed along the whole length of 
 the chimney. When the source of heat is as usual at the 
 bottom, each particle of air loses some of its heat, and
 
 ARTIFICIAL VENTILATION. 75 
 
 therefore some of its tendency to rise in passing out ; but 
 the retardation due to this cause is slight in comparison 
 with the momentum which has been stored up by previous 
 impulses. Even this loss of heat may not occur if we are 
 to credit the testimony of practical architects. E. E. 
 Rice, of Washington, inventor of a system of ventilation, 
 says : "I find in practice the highest temperature imme- 
 diately below the level of the roof." If this be true, it 
 furnishes still further reason for upward acceleration. 
 
 In some systems of heating and ventilating now in 
 use the foul-air tubes are carried down and admitted to 
 the chimney beneath the fire. It might at first seem that 
 this arrangement would give a stronger draught, on ac- 
 count of the fact that this air is depended upon to supply 
 the combustion in the chimney, but when wholly de- 
 pended upon for this purpose the fire will lack much of 
 that vigor of combustion upon which the aspirating power 
 of the chimney will mainly depend. Air which has already 
 been robbed of much of its oxygen, and been contaminated 
 with the products of respiration, is a poor supporter of 
 combustion. It appears, therefore, that in order to give 
 the chimney its greatest aspirating power, the fire should 
 be fed with pure air. It is as poor economy to feed a fire 
 with C0 2 as to feed pupils with it. Whatever intensifies 
 the fire increases the draught. 
 
 The power of a strong upward current of air in a 
 chimney to abstract air from tubes opening into it will 
 be better appreciated by remembering that some of the 
 most effective air-pumps are constructed on precisely this 
 principle. An almost perfect vacuum can be made in a 
 vessel leading by a tube to another tube through which a 
 column of water is falling. In Bunsen's pump, con- 
 structed on this principle, water is used ; and in Spren- 
 gel's, mercury. In an aspirating chimney the moving
 
 76 VENTILATION AND WARMING OP SCHOOL-BUILDINGS. 
 
 current is gaseous instead of liquid, and, although less 
 effective, is sufficiently so to create a powerful draught. 
 In view of this fact, it might be better in a house above 
 one story to carry all the ventilating tubes to a main tube 
 extending up nearly to the roof before opening into the 
 chimney. 
 
 Owing to the fact that the momentum of columns of 
 air is proportional to their volume, aspirating chimneys 
 should be built as high as convenient. Where buildings 
 are heated by steam, the draught in aspirating chimneys 
 may be created by carrying steam jets into them ; the 
 escaping steam causing a partial vacuum, which is filled 
 by air coming from below toward the direction taken by 
 the steam. See Fig. 11, where C represents the aspirating 
 chimney, B the boiler, F the furnace, L> the air-duct. 
 
 FIG. 11. 
 
 M 
 
 The arrows show the direction of the current. The steam 
 thus issued into a chimney will set in motion a body of 
 air about 217 times its own bulk. When steam is used,
 
 ARTIFICIAL VENTILATION. 77 
 
 the foul-air tubes would perhaps better be placed below 
 the jets, as it would in this case be no interference to com- 
 "bustion, and the chief vacuum - producing power is, in 
 this case, where the steam is escaping. 
 
 In buildings furnished with burning-gas, a few jets 
 kept burning in a chimney are often sufficient to produce 
 the requisite draught. In summer this will be all-suffi- 
 cient. General Morin found that one cubic foot of gas is 
 sufficient to set in motion 1,000 cubic feet of air. 
 
 Where buildings are heated by steam, it is better to 
 run a coil of steam-pipe into the base of the shaft. The 
 following formula, deduced by Prof. W. P. Trowbridge, 
 may be found useful for determining the amount of 
 steam-pipe necessary to be put at the base of an aspirat- 
 ing chimney in order to maintain the desired draught : 
 
 Tirrri 
 
 S = TfTm ^-rX 1,500, where S = number of square feet 
 
 ' 
 
 in exterior surface of the coil at the base of the chimney; 
 Ta = absolute temperature of the external air that is, 
 the common or thermometric temperature plus 459 '4;* 
 W = weight of air in pounds which is discharged in 1 
 second ; H = height of flue ; Ts = absolute temperature 
 of the steam in the pipe. The constant 1,500 is deter- 
 mined from other constants which were employed in de- 
 
 * The absolute temperature is obtained from the relations which ex- 
 ist between the temperature of a body and its rate of expansion. If air 
 at C. be heated, its volume will be increased -^rs of its original vol- 
 ume for every degree raised. Then its volume will be doubled when 
 273 is reached. If it be cooled below 0, its volume will be diminished 
 yfj for every degree lowered. If this diminution should proceed at the 
 same ratio till 273 is reached, its volume would be nothing. This is, 
 of course, true only theoretically, as it is impossible to freeze matter out 
 of existence. But this point is taken as absolute zero, which when used 
 makes all temperatures positive. Reduced to the Fahrenheit scale, it is 
 459-4.
 
 78 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 ducing the formula ; they were : the force of gravity, 
 specific heat of air, ratio of transfer of heat to air by 
 coils, and the ratio between the theoretical and actual 
 Telocity in the flue. 
 
 Steam-coils are used for the purpose here named in 
 Columbia College, New York, where the heating and ven- 
 tilating apparatus was arranged by Prof. Trowbridge. 
 They are also used in the Johns Hopkins University of 
 Baltimore. 
 
 It is always best when possible to have the ventilating- 
 flue combined with the smoke- chimney, so as to utilize 
 the heat of the waste products of combustion. When 
 heat from this source is insufficient, it can be supple- 
 mented by the use of the steam-coils. 
 
 CHAPTER XII. 
 
 THE MOVEMENT OF TFE AIE BY MECHANICAL MEANS. 
 
 The Vacuum Movement. A current of air through a 
 room for the purpose of ventilation is sometimes produced 
 by putting into the ventilating or foul-air duct an extract- 
 ing fan, Archimedean screw, pump, or blower. Such an 
 arrangement may take the place of an aspirating chimney, 
 or by being put into the chimney become a part of it, sup- 
 plementing its draught-producing function. The func- 
 tion of mechanical propellers, when put in the foul-air 
 duct, is always the same, that of producing a partial 
 vacuum in the room by extracting the foul air, thus 
 making room for a fresh supply, which will find its way 
 in by openings provided for that purpose. 
 
 When mechanical means are thus made use of, it of
 
 MOVEMENT OF THE AIR BY MECHANICAL MEANS. 79 
 
 course makes no difference, in the rapidity of change 
 which the air in the room will undergo, whether the pro- 
 peller be placed in the foul-air duct and draws the air 
 through the room, or whether it be placed in the fresh- 
 air duct and pushes the air through the room, for in 
 either case the propeller moves the same quantity of air. 
 
 Whatever is forced in must find a way out, and what- 
 ever is drawn out must be supplied by inlets. When air 
 is thus drawn out, it is a vacuum-forming process, and 
 the pressure of air on the inner parts of the room will be 
 somewhat less than that on the outside. Currents of air, 
 therefore, through small openings, cracks, windows, as 
 also from halls, closets, etc., will be inward ; the quality 
 of the air, therefore, will be determined by the character 
 of the inlets, and the function of the intended inlets may 
 be usurped by an open door delivering air too cold, an 
 open closet delivering impure air, or an elevated crack or 
 other opening delivering air too high up to be utilized, 
 and so drawn out unused. 
 
 Another objection to this manner of drawing the air 
 through the room, especially where the draught is from 
 several rooms, is that the draught will not be equal. In 
 rooms which have their inlets through tubes compara- 
 tively short, where the incoming air encounters very little 
 friction, the supply will be ample and at the expense of 
 more remote rooms to which the air must pass through 
 long tubes and perhaps pass abrupt angles. The relative 
 draught will also fluctuate with changes in the force and 
 direction of the wind, sometimes favoring one side of the 
 house, sometimes another. 
 
 The Plenum Movement. Instead of drawing the foul 
 air from the room by placing the propeller in the exit 
 shaft, the pure air may be forced in by placing the pro- 
 peller in the inlet duct. This may be called the plenum
 
 80 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 movement, and produces in the room a perflating instead 
 of a vacuum-forming tendency. 
 
 The plenum has many advantages over the vacuum 
 movement. In this movement the atmospheric fullness 
 in the room, produced by perflation, causes all currents 
 through accidental openings to be outward instead of 
 inward, thus preserving the air of the room from the 
 incidental external impurities of closets, cellars, base- 
 ments, etc. 
 
 The plenum movement has not received the attention 
 which its usefulness demands. Much as may be said in 
 favor of natural ventilation, and evident as it is that all 
 successful ventilation must depend on a studious and 
 skillful conformity to the few natural laws underlying 
 the whole process, it will still remain questionable, after 
 everything possible has been done to produce draught 
 by differences of height and temperature, whether it 
 is possible to supply at all times a large school-house 
 full of pupils with air of the necessary quantity and 
 quality. 
 
 We have seen in preceding pages how fast air must 
 pass through a room in order to supply the 'requirements 
 of respiration. We have also seen that this current must 
 be properly distributed and be of a certain temperature 
 and humidity. Now these conditions are approached in 
 different degrees by different systems of heating and ven- 
 tilating ; but in no system has the ideal been reached 
 without the aid of mechanical means. 
 
 There are many good systems now in use, the in- 
 ventors of which deserve great credit for much good 
 work toward solving the great problem of warming and 
 ventilating. But the efficiency of none of these systems 
 is quite commensurate with the claims of their inventors. 
 The comparative merits of some of the best systems now
 
 MOVEMENT OF THE AIR BY MECHANICAL MEANS. 81 
 
 in use are discussed in another place, where the prin- 
 ciples involved in each are examined. 
 
 The assertion which I here venture, that perfect 
 warming and ventilating has not been attained without 
 the aid of mechanical means, is easily demonstrated on 
 general principles. What is implied in perfect ventila- 
 tion ? As an example of it, we might suppose the case 
 of a balmy spring day, when a gentle breeze, barely per- 
 ceptible, is passing through the wide-open opposite win- 
 dows of a room situated in a salubrious locality. In this 
 case the air is of a genial warmth. It has not been blown 
 across a burning desert or through an artificial furnace. 
 It does not enter the room scorching hot, where it mixes 
 with other air icy cold. It is not kept in the room till it 
 has become dangerously impure ; but in passing directly 
 through it gathers the impurities of the passing breath 
 and carries them away as fast as formed, leaving the 
 room while still in a state of respirability. 
 
 Now this may be produced artificially, by warming 
 the air to the proper temperature and forcing it through 
 the room by mechanical means, but by any other means 
 now in use it is impossible. A little reflection will make 
 this plainly evident. 
 
 We have previously seen that when adequate ven- 
 tilation is maintained by an upward current through 
 the room, it is caused mainly by the difference between 
 the internal and external temperatures and the vacuum- 
 producing power of aspirating chimneys. But how is 
 this difference of temperature in very cold weather to bo 
 produced ? If by stoves, the temperature in different 
 parts of the room will be unequal some parts hot, and 
 other parts cold ; if by the direct radiation of steam 
 pipes, the entering air is cold, and, although it be warmed 
 by passing over the heater, it will be warmed unequally
 
 82 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 and imperfectly. If by warm air entering the room, it 
 must enter fast enough to change the air in the room 
 about every seven minutes ; but air of this temperature 
 will not enter thus rapidly by any ordinary medium of 
 pipes and tubes, on account of friction, etc. 
 
 The main cause of the inflow of the warm air is the 
 difference of its specific gravity due to heat. For the 
 inflow to be rapid the heat must be great, but hot air 
 must be ruled out of the legitimate conditions of perfect 
 ventilation. It is, I think, possible to pass air not above 
 a temperature of genial warmth when it enters, in suffi- 
 cient quantities to serve the ends of ventilation, and 
 sufficiently to warm the room in cold weather, but it re- 
 quires a different arrangement of pipes and furnaces than 
 has yet been put in practice, and might exceed in cost a 
 good plenum movement. 
 
 CHAPTEE XIII. 
 
 AIR-PKOPELLERS. 
 
 THE problem of setting in motion quantities of air 
 sufficient to supply the requirements of ventilation, and 
 to so direct this air as to approximate a maximum of 
 movement with a minimum of expended power, is a me- 
 chanical problem which becomes important in considering 
 the plenum movement, both from the standpoint of work 
 accomplished and the economy of accomplishing it. 
 
 Of propellers for moving air, many kinds have been 
 used, among which may be mentioned those of Combs, 
 Kittenger, Hales, Letoret, Howorth, Eoots, Glepin, Ar- 
 nott, Chaplin, Perrigault, Lloyd, Fernie, Hendry, Hope,
 
 AIR-PROPELLERS. 83 
 
 and Blackman. Most of these are in some form of revolv- 
 ing fan, the floats of which are so placed as to set in motion 
 the air outward radially, thereby creating a partial vacuum 
 near the axis, thus setting more air in motion as it is filled. 
 The object of a propeller is not only to set in motion 
 large quantities of air, but to set it in motion in such a 
 manner as not to produce loss by opposing counter cur- 
 rents and by useless friction. Air, on account of its ex- 
 treme mobility, requires primarily very little power to 
 move it, but when it is forced through small apertures, 
 or set in motion in such a way as to produce cross cur- 
 rents, great power may be required to accomplish a little 
 work. Dr. Arnott observed this in the working of re- 
 volving fans, and invented a ventilating pump which he 
 put in operation in a hospital. So conserved was the 
 power by the construction of his propeller that the entire 
 building was supplied with air by the motive power de- 
 rived from the descent of the water used- in the building 
 from a high reservoir to the basement. It may be re- 
 marked here that everything which Dr. Arnott devised for 
 the improvement of ventilation possessed singular and 
 unusual merit.* Since Dr. Arnott's time, however, con- 
 siderable improvement has been made in revolving fans 
 and other propellers. 
 
 * As before mentioned, Dr. Arnott never secured the exclusive right 
 to his inventions by letters patent, but in a true philanthropic spirit 
 gave the results of his labors to the world. It is douttful, however, 
 whether this did not hinder rather than promote the propagation of his 
 ideas. It is noteworthy that while these inventions are acknowledged to 
 be superior to most others, and are free to everybody, they have been 
 comparatively little used. Had the worthy author secured his inventions 
 by letters patent everybody would be ready to scrutinize their merits and 
 pay the price ; but when a gift is offered it is little regarded, so prone 
 is human nature to think it impossible for a man to give away that which 
 is of value. 
 9
 
 84 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 The objection which has heretofore been made to the 
 plenum movement is its expense. Owing to the extreme 
 mobility of air, the power required in merely moving it is 
 theoretically almost nothing ; the expense, then, must 
 result from the manner of moving it from forcing it 
 through small apertures, and from friction and collision 
 due to misdirecting it. The construction of the machines 
 for propulsion is, therefore, of so much importance in 
 the economy of mechanical ventilation that I shall notice 
 at some length the construction and efficiency of some of 
 the earlier and later types of revolving propellers. 
 
 Rittenger's Fan. Fig. 12 represents Kittenger's fan. 
 A is a side view showing the shell y, which is of the form 
 
 FIG. 12. 
 
 B 
 
 6. 
 
 \ 
 
 \ 
 
 of an Archimedean spiral, beginning at e ; the radius of 
 the inlet r 2 , the outer and inner radii of the vanes r and 
 r 1 , the radii I of the curve of the vanes ; the angle z be- 
 tween the radius and the initial line of the vane. B is a 
 section on the line xx'. The arrows show the direction 
 of the current,
 
 AIR-PROPELLERS. 85 
 
 The construction of this fan shows that its design is, 
 first, by the angle z, to produce a motion of the air ra- 
 dially, producing a vacuum-forming tendency at the cen- 
 ter, causing the air to be pushed in toward that point 
 from the outside ; and, second, by curving the vanes 
 forward, to direct the tangential motion of the air as far 
 as possible toward the outlet duct. 
 
 To understand the action of the vanes on the air, sup- 
 pose a single particle of air at p struck by the vane as it 
 reaches that point in its revolution. If the angle z were 
 0, then the particle would be impelled forward on the 
 tangent p' p', but as the angle z increases, the direction 
 taken by p will be more radial, the amount of this change 
 of direction being proportional to the sine of z, the rela- 
 tion holding between and 90. If the vanes be straight, 
 increasing z will give the air a receding tendency ; this 
 the curve is intended to prevent. Now, the nature of 
 this curve is of course important. Its radius of curvature 
 
 r" r * 
 is expressed by Rittenger by the formula I = = 1 ^, 
 
 where r outer radius of the vanes, r, = inner radius of 
 the vanes, z = the angle between the radius and the 
 initial line of the vane, and I = radius for the curvature 
 of vanes. The formula shows that as the vanes are nar- 
 rowed, or as r 1 r* is diminished, I will decrease. Refer- 
 ence to the figure, with a little mechanical conception, 
 will prove the general correctness of these relations. For, 
 if we imagine r 1 to be increased, thus narrowing the fan, 
 the particle of air p will have its distance from the shell 
 diminished, so that when deflected radially by increasing 
 z it would have a sharper curve to give it the required 
 forward impulse than when it started from a greater dis- 
 tance, giving more time for deflection. 
 
 The formula shows, further, that as sine z (or z) is
 
 86 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 increased I will be diminished. Referring to the figure 
 again, the reason becomes evident. For as z is increased 
 the particle of air p will be deflected more radially ; to 
 counteract this before the circumference is reached the 
 curve must be made sharper I must be lessened. 
 
 The effect which in this fan is realized in practice is 
 about forty per cent of the power expended. Yet this is 
 one of the best fans which have been thoroughly tested. 
 Surely there is an open field in the economy of applied 
 power for the mechanical engineer. 
 
 In this fan, it appears to me that much of the loss of 
 effect comes from beating the air too much radially, and 
 not enough tangentially ; or, rather, that the radial and 
 tangential forces are not properly distributed. In this 
 case the direction of the impulses is too much outward 
 on the shell, and not enough forward toward the duct. 
 Now, this can be partially corrected in making the curve 
 of the vane elliptical instead of circular, where each vane 
 
 comprises one fourth of the ellipse. I would therefore 
 
 f r * r *\ e 
 
 propose the following modified formula : I = ^ . 0> 
 
 2 r l sine * 
 
 where I = semi-major axis of the ellipse, e = the ratio be- 
 tween the major and minor axes, and r, r,, and z = same 
 as in the preceding. This relation shows that e increases 
 with the width of the vanes, and also with the length of 
 the semi-diameter of the curve. 
 
 The amount of work which is required to deliver any 
 given amount of air by means of fans may be calculated 
 
 62-5 100 
 
 by the formula Hp. = - X X V h, where Hp. = 
 
 550 x 
 
 number of horse-powers, 62 '5 = weight of a cubic foot of 
 water, 550 = number of pounds in one second by one 
 horse-power, x = per cent of efficiency, V = volume of 
 air delivered in cubic feet per second, h = the relative
 
 AIR-PROPELLERS. 
 
 87 
 
 weight of the air compared with an equal bulk of water. 
 As the air is denser than normal when being forced 
 through the ducts, h must be determined by the ma- 
 nometer. V can be found by means of an anemometer. 
 (See Appendix C.) 
 
 Combs' s Fan is of different construction, but as its 
 per cent of efficiency is somewhat less than that of Kit- 
 tenger's it will not here be discussed. 
 
 Fm. 13.
 
 88 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 Blackmaris Fan (see Fig. 13). As an example of mod- 
 ern improvement in revolving fans, I copy from the 
 patent-office specifications the description of what seems 
 to me one of the best yet constructed (see Appendix F). 
 
 TJie Hope Fan. An improvement on the Blackmail 
 Fan has recently (1886) been patented by Hope Brothers, 
 of Kansas City, Missouri. The improvement consists of 
 a slight modification of the vanes, and the conversion of 
 the whole fan into a water motor, which is the power 
 used. 
 
 This fan motor undoubtedly possesses some advan- 
 tages over any other yet devised. It can be used either 
 as an exhauster or a perflator, and, by being placed di- 
 rectly at the entrance into the room, the loss from fric- 
 tion of moving air through long ducts is prevented. By 
 applying the power at the circumference of the wheel, 
 instead of near the center, as is usual when belting from 
 an engine, much power is gained, especially when a rela- 
 tively small quantity of water is used under high pressure. 
 
 Of course, when other things are equal, no gain would 
 be realized by applying the power at the circumference, 
 as what is thus gained in power would be lost in velocity, 
 but in the case supposed, where a small stream of water 
 under high velocity is used, much of the effective power 
 will exist in its vis viva as it strikes the buckets. Now, 
 as the vis viva is proportional to the mass of the moving 
 body, and to the square of its velocity, the increase of 
 velocity will be more effective than an increase of mass. 
 
 One of these fans is adequate to move the air of a 
 school-room of ordinary size. It can be run for five cents 
 per hour, as proved by actual experiment in Kansas City, 
 when the water pressure is eighty pounds. 
 
 Patent of Hendry and Others. One of the most ad- 
 vantageous arrangements is to put the fan in the angle of
 
 AIR-PROPELLERS. 
 
 89 
 
 the shaft and ventilating duct, as illustrated in Fig. 14. 
 The advantage gained in this arrangement consists in car- 
 
 FIG. 14. 
 
 B 
 
 rying the entering air only one fourth of a revolution be- 
 fore releasing it. 
 
 In the figure, the arrows show the direction of the 
 fan's revolution, and also the direction taken by the air. 
 As the vane a is moving forward in its present position it 
 carries in front of it the air in the lower part of the shaft 
 A ; the tangential motion which the revolution gives to 
 this air will, when one fourth of a revolution has been 
 made, send it through the duct B. This manner of plac- 
 ing the fan is used by A. J. Ilendry, of Georgia, in an 
 invention patented in 1883. The amount of friction
 
 90 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 which this arrangement obviates would allow the use of 
 clock motors which could be wound up at stated inter- 
 vals. A shaft and tube could be supplied each room, and 
 the motors thus distributed would furnish ample power 
 for propulsion. 
 
 The plenum movement, so far as at present attained 
 in practice, will deliver from fifty to one hundred and 
 fifty cubic feet of air per horse-power per second. But 
 these estimates have been made irrespective of accompa- 
 nying effects of natural ventilation. In arranging for the 
 plenum movement every provision should also be made to 
 derive all possible aid from natural movement. When- 
 ever it is possible to ventilate by natural means, the me- 
 chanical means could be suspended. It should be the 
 object of the plenum movement to supplement the natu- 
 ral, not to replace it. By working with Nature as an aid 
 the amount of power required would be greatly lessened. 
 
 CHAPTER XIV. 
 
 CAN THE PLENUM MOVEMENT BE AFFORDED ? 
 
 IN order to answer this question understand ingly it 
 will be necessary to enter into somewhat lengthy detail 
 concerning the amount of heat needed, the amount of 
 unavoidable waste, and the amount of fuel necessary to 
 the supply ; then to consider the cost of adding thereto 
 the cost of the plenum movement, and to compare the 
 total estimate thus made with present expenditures. 
 
 In making these estimates I shall consider a single 
 room, of average size, and supposing the average conditions 
 as to exposure, number of windows, locality, etc. The
 
 CAN THE PLENUM MOVEMENT BE AFFORDED? 91 
 
 Maximum number of 
 degree* tempera- 
 tmre to be raised. 
 
 Average number of 
 degrees tempera- 
 ture to be raited. 
 
 Mean temperature of | 
 fire months. 
 
 No. of montiu fir 
 required. 
 
 i i 
 
 i i T i 
 
 T-T- <- 
 
 * 
 
 1- oo oo i- o co oo i> i> t* 
 
 g 
 
 >.;Mean. 
 
 * 
 
 nssggssssgsgg sgsssss 
 
 
 
 
 3 -t>o
 
 2 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 table on page 91 shows the minimum and mean tempera- 
 tures of each month, compiled from observations of the 
 Signal Service, U. S. A., and Blodgett's "Climatology of 
 the United States." As the table shows, the amount of 
 heat required depends partly on the latitude and locality 
 of the place. I select for our estimate that of Chicago, as 
 representing a high average, but, of course, at places far 
 north or south, other figures will be found in the table 
 which will be more appropriate. 70 is taken as the tem- 
 perature of comfort, and to which existing temperature 
 must be raised. Taking seven as the number of months 
 fire is required ; the average temperature of these months 
 35 ; then the average number of degrees of temperature 
 to be raised will be 70 35 = 35. Taking the average 
 number of pupils in one room as 60, the cubic feet of air 
 required in one hour will be 60 X 3,000 = 180,000. A 
 thermal unit, or unit of heat, is the amount of heat re- 
 quired to raise one pound of water one degree. By careful 
 experiment and comparison of the specific heats of air and 
 water, it is established that this amount of heat one 
 thermal unit will raise 48 cubic feet of air one degree. 
 
 180,000 
 
 Then ^ = 3,750 = number of thermal units neces- 
 sary to raise 180,000 cubic feet of air one degree, and 
 3,750 X 35, the average number of degrees to be raised, 
 equal 131,250, the number of thermal units necessary to 
 supply the occupants of one school-room one hour. 
 
 Loss through the Walls. The formulas which it will 
 be necessary to use in making these estimates may seem 
 difficult, but they have been deduced from well-known 
 laws and properties of matter familiar to every physicist, 
 and formulated by the best European mathematicians. 
 They are in practical use by skilled engineers everywhere. 
 The loss of heat through walls, when all sides of the build-
 
 CAN THE PLENUM MOVEMENT BE AFFORDED? 93 
 
 ing are exposed, may be calculated from the formula U = 
 
 , * , . : ~. where U= total units of heat lost per 
 
 C (2 l*+r)+el-tq 
 
 hour per square foot ; I* loss by contact of air for a 
 difference of 1 = '4912 when the air is moving ; C = con- 
 ducting power of material (see table, Appendix D, page 
 167); r = radiating power of material (see table, Appendix 
 E, page 168) ; q = r + It ; T = temperature of air in the 
 room ; T, = temperature of external air ; e = thickness of 
 wall in inches. The loss of heat through floors and ceilings 
 when not exposed to the external air is usually regarded 
 as null. Taking 26 feet X 34 X 14 as the size of the 
 average school-room, 120 X 14 = 1680, area of walls in 
 square feet. Counting six windows, each 9 X 3 feet, 
 9 X 3 X 6 = 188, area of windows ; 1680 188 = 1492 
 square feet of wall surface. The wall is supposed to be 
 18 inches thick. 
 
 The values in this example to be used in the above 
 formula will be I, = -4912 ; c = 4-83 ; q = r + I, = -7358 
 + -4912 = 1-227 ; r = '7358 ; e = 18 inches ; T = 70 ; 
 T, = 35. Then 
 
 n -4912X4 -83 XI '227X35 _101-88__ 
 
 ~4-83 (2X4-912+ -7358)+18x4-912xl-227~ 19-13 ~ 
 5-32 = thermal units per square foot per hour; 5 -32 X 
 1492 = 7937-44 = thermal units lost through the walls in 
 one hour. 
 
 Loss through Windows. "When the windows are not 
 more than inch in thickness the following formula is 
 used for finding the value of U : U = q (T ( 4 ), where 
 t t temperature of the glass ; q = r -\- It ; r = radiating 
 power of the glass ; h = loss by contact of air for a differ- 
 ence of 1 = -4912. 
 
 The values in this example are, q = (r + It) = (-5948 
 + -4912) = 1-086, T = 70 ; t t = *f-= 17*5 J then U =
 
 94 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 1*086 X 17*5 = 19 = thermal units per square foot. 
 Area of six windows = 188 square feet X 19 = 3572 = 
 loss through the windows in one hour. 
 
 Total Loss. 
 
 From incoming fresh air ............ 131,250 
 
 From walls ...... ................... 7,937 
 
 From windows ...................... 3,572 
 
 Total thermal units ............ 142,759 
 
 Now, in the burning of one pound of coal 13,000 ther- 
 mal units are evolved. The efficiency of a heating appa- 
 ratus depends upon the amount of surface exposed and 
 skill in firing. In practice, the efficiency of heaters is 
 from 38 per cent to 80 per cent of the whole heat evolved. 
 Taking 60 per cent as a fair average of efficiency, 
 
 142,759 100 
 
 ' X -777- = 18'3-J-, number of pounds of coal re- 
 lo,000 oO 
 
 quired for one room for one hour. From this as a unit the 
 
 cost for a building of any number of rooms may be obtained. 
 
 For example, counting seven the number of fire 
 
 months, eight as the number of hours per day in which 
 
 fire will be needed, $5 the price of a ton of coal, the cost 
 
 of heating a building of ten rooms would be, 
 
 18-3 X 20 X 7X 8 X 5X 10 
 
 2000 
 
 Now, under the conditions supposed, this will be the 
 necessary expense ; any less would imply that the chil- 
 dren and teachers are fed on impure air. To heat such 
 vast quantities of air as the conditions of sufficient venti- 
 lation necessitates requires large expenditures of heat. 
 There is no help for this. The rations of pure, life- 
 giving air measured out to children shut up in close 
 houses should be as certain a quantity as the daily allow- 
 ance of bread and butter.
 
 CAN THE PLENUM MOVEMENT BE AFFORDED? 95 
 
 By examining reports of school boards from various 
 cities I find that the expenditure above calculated is 
 not far from the actual average cost of supplying such 
 school-houses similarly conditioned. That is to say, the 
 present expenditure for fuel is sufficient to supply the 
 most rigid demands of sanitary ventilation. 
 
 "We are not ready, however, to conclude that all is 
 well. The coincidence of these facts proves nothing. 
 There would have to be an important additional element 
 to make these two first facts possess a causal relation to 
 each other. If the school expending this amount of fuel 
 should be visited by an expert who, after examining the 
 air, testing for C0 and noting the rate of renewal, found 
 that the air was being renewed every six to seven minutes, 
 and the CO* not above *2 per 1000 of air, then the con- 
 clusion would follow that the expenditures had been made 
 economically. 
 
 But, unfortunately, this important third element is 
 wanting. The real facts are too well known to admit of 
 any mistake here. Instead of the air of the average 
 school-room being changed every six minutes, it is not 
 changed oftener than once in thirty minutes, and more 
 frequently probably not oftener than once per hour. In 
 thousands of houses it is not changed at all, just enough 
 air working its way in by diffusion to prevent immediate 
 death by suffocation. 
 
 These are the facts. It would be tedious to enumer- 
 ate the commissions which have from time to time in dif- 
 ferent parts of the world been appointed to investigate 
 this subject. Whjle there is variety in the character, 
 number, and locality of these investigations, there is 
 singular unanimity of results. The invariable verdict 
 of all may be epitomized as bad, BAD, BAD ! Some are 
 better than others (or, rather, some are not so bad as 
 10
 
 96 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 others), but the difference is rather in degree than in 
 kind. 
 
 The question which now confronts us is, What became 
 of the heat from all of that coal ? There is but one an- 
 swer : It was wasted. There may be many sources for 
 this waste. Windows and doors are thrown open to re- 
 lieve the temporary inconvenience of a depressing atmos- 
 phere. These openings, especially when near the heater 
 or incoming warm air, at once become outlets, setting 
 the current toward them, and drawing out the warm, 
 pure air as fast as furnished. 
 
 Too small heating surfaces or unskillful firing may 
 also be causes of waste. Overheating the air and con- 
 fining in the top of the room (as is the practice of some 
 hot-air systems) till it cools down to the temperature of 
 comfort is a positive waste by conduction through the 
 upper walls and windows. . The only way to utilize the 
 excess of heat in supra-heated air would be to thoroughly 
 mix it with such an amount of cold air as would be re- 
 quired to reduce the temperature to that of comfort. 
 
 In view of this state of the case, what is the remedy ? 
 How is the heat which is being expended to be utilized ? 
 The answer is evident. There must be some means 
 whereby the air in a room may be changed with requisite 
 frequency, and this independent of the doors and win- 
 dows. The heating surface must be properly propor- 
 tioned to the amount of fuel consumed in order to lessen 
 the waste through the smoke chimney. Air must not be 
 heated much above the temperature at which it is to be 
 used,' in order that there may not be loss in cooling. 
 
 We return now to the original question, Can the 
 plenum movement be afforded ? Can the extra expense 
 of moving this air through the building be assumed by 
 the people ? This, it seems to me, is much like the
 
 THE COST OF VENTILATION. 97 
 
 question of a man who, after having paid a high price for a 
 stove, asked his wife if they could afford the coal to build 
 a fire in it. Not to provide the means of utilizing ex- 
 pense already incurred is simply to waste this expense. 
 
 I am aware that many economize by an exact count 
 of dollars and cents concerned in immediate expenditures. 
 But to this question true economy has but one answer : 
 TJiis air must in some way be moved. If it can be done 
 by aspirating chimneys, of proper size and construction, 
 very well ; if not, it must be moved by mechanical means. 
 At all events, it must be moved by some means. 
 
 CHAPTER XV. 
 
 THE COST OF VENTILATION. 
 
 Cost of the Aspirating Chimney. Let us approximate 
 the cost first of the aspirating chimney. We have seen 
 (see Appendix B) that where the fresh-air inlets are of 
 adequate area the velocity of the air in the ducts should 
 be at least 7*7 feet per second, say 8 feet. Assume the 
 height of the aspirating chimney to be 70 feet. 
 
 To find the sectional area of an aspirating chimney 
 which is to take away all the air that passes in one hour, 
 
 V 
 
 we have A = ... ... , where A = the sectional area of the 
 
 00,000 v 
 
 aspirating chimney ; V = volume of air passing through 
 the chimney per hour ; v = velocity of air per second in 
 ducts ; 3,600 = seconds in one hour. Then the sectional 
 area of a chimney required for a single room in our exam- 
 
 . , . 180,000 
 
 plo above is A = - -f- -- = 6 -2 square feet. The ve-
 
 98 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 locity of the air will depend upon the difference of tem- 
 perature between the air in the chimney and the air 
 outside. 
 
 Now, the number of degrees temperature which the 
 air in the chimney will have to be raised in order to 
 produce a velocity of 8 feet (or other given rate) may 
 
 v *(l+et}(l+f l -+f\ 
 
 be formulated : / = ' - ft - t), 
 
 2gh 
 
 where t s = increase of temperature by fire ; v = velocity 
 of air in feet per second in ducts ; e = expansion of air 
 per 1 temperature = '00203 ; t = external temperature ; 
 f= co-efficient of friction in ducts ; 1= total length of 
 ducts ; d = diameter of ducts ; U = internal temperature 
 of room ; g = accelerated gravity ; h = height of chim- 
 ney ; /i = co-efficient of friction in elbows. 
 
 The corresponding values in our example are : v* 
 8' = 64 ; e= '00203 ; t = 35 ; / = -05 (for rough flues) ; 
 fi = 4'5 (assuming three square elbows, which is proba- 
 bly a fair average) ; I = 180 (this includes the height of 
 the chimney, the height of the pure-air shaft, and the 
 ducts) ; 180 is a fair average ; d = 2 '5 (for estimate made 
 on necessary size of total inlets, q. v.) ; g = 32 '16 ; h = 
 70 feet ; ti = 70. Substituting these values : 
 
 64 (1 + -00203 X 35) ( 1 + -05 ~^- + 4's) 
 
 / _ l_ J~-ZJ 35 = 
 
 2 X 32-16 X 70 X '00203 
 
 - 
 "' 
 
 The quantity of coal necessary to produce any given 
 
 / s W 
 temperature is -expressed K = - r- , where K = number 
 
 of pounds of coal per hour ; s = specific heat of air = 
 238 ; W = weight of air in pounds carried off per hour ;
 
 THE COST OF VENTILATION. 99 
 
 u = units of heat utilized in one pound of coal when 
 burned on a grate = 6000 ; % = per cent of loss by radia- 
 tion through wall of chimney = '9. 
 
 Present values.: t t = 33-35 ; a = '238 ; W = 14,400 
 pounds (weight of 1 cubic foot of air at 35 being -08, then 
 180,000 X '08 = 14,400) ; % = -9. Substituting : K = 
 
 33-35 X '238 X 14,400 , , , , . 
 -r r = 21, the number of pounds of 
 
 Oj^rUly 
 
 coal necessary to burn per hour on a grate in the chimney 
 in order to secure sufficient ventilation. 
 
 This, it will be observed, is more by nearly 3 pounds 
 per hour than was found to be required for heating. 
 Evidently, then, coal burned on a grate in an aspirating 
 chimney, for the purpose of creating a draft, is expensive. 
 Can it be afforded ? If there were no better way to ac- 
 complish the same work there would be bat one answer : 
 Yes, of course, it can be afforded, for the children and 
 teachers must have air. 
 
 But this supposed expense is not necessary. Instead 
 of heating the aspirating chimney, as heretofore described, 
 it may be combined with the smoke chimney, which will 
 generally, if properly constructed, be sufficient to heat 
 the aspirating chimney to the required degree. This 
 may be done, has been done, in various ways. The foul- 
 air ducts may lead to an aspirating chimney built around 
 the smoke chimney so as to be warmed by it. They may 
 open directly into the smoke chimney, either above or 
 below the fire, or they may be carried up to near the top 
 before entering. On account of a possible tendency to 
 smoke in windy weather, it is probably best to have the 
 chimneys so arranged that the heat from the smoke chim- 
 ney may be utilized in the aspirating chimney without 
 direct communication between them internally. To effect 
 this, I would suggest that the smoke and escaping heat
 
 100 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 from the heater be carried off through a large number of 
 small metallic tubes extending up through the chimney. 
 The large surface thus exposed to the air inside the chim- 
 ney would thoroughly heat it to the temperature required 
 in an aspirating chimney. 
 
 In Fig. 15, C represents the wall of the chimney ; F, 
 the furnace ; the lower arrows, the course through the 
 
 FIG. 15. 
 
 tubes taken by the smoke ; D, the foul-air duct leading 
 from the school-room ; the upper arrows, the course be- 
 tween the tubes taken by the foul air. A number of 
 small-sized stove-pipes would answer well for the tubes. 
 In this case the chimney would have to be made large 
 enough, so that a cross-section of the chimney, minus the 
 sum of the cross-sections of the tubes, would leave a
 
 THE COST OF VENTILATION. 101 
 
 remainder equal to the required size of aii aspirating 
 chimney. 
 
 The main trouble with aspirating chimneys has been 
 from making them entirely too small. We saw above 
 that the sectional area necessary for a single school-room 
 is over 6 square feet. Calling it 6, then, for six rooms, 
 it would be 36 square feet 6 feet square. For eight 
 rooms, 48 square feet nearly 7 feet square. For four- 
 teen rooms, 84 square feet over 9 feet square. In the 
 arrangement above illustrated the necessary area for 
 smoke-flues must be added to these numbers to obtain 
 the size which the chimney would have to be built. 
 
 To calculate the area of smoke-flues, engineers usually 
 
 jr 
 
 use the formula A = *128 . where A = sectional area 
 
 Vh 
 
 in square feet ; K = pounds of coal consumed in one 
 
 hour ; *128 = a constant ; h = height of chimney in feet. 
 
 The corresponding values in the present calculation 
 
 I 0.0 
 
 are : K = 18-3 ; h = 70. Then A = -128 ^~ = -279 
 
 V70 
 
 square feet = '279 X 144 = 40-1 square inches. We found 
 above that the necessary area of an aspirating chimney 
 for one room is 6 '2 square feet = 892 '8 square inches ; 
 40 '1 inches being '044 of 892 '8 square inches, the en- 
 tire size of the chimney, including smoke- and foul-air 
 flues, may be found by multiplying the necessary aspirat- 
 ing chimney area by 1'044. Then 6*2 square feet, the 
 area of an aspirating chimney for one room, multiplied 
 by 1'044 = 6 '472 square feet. This is sufficient to show 
 that the chimneys, when intended for the double purpose 
 of carrying smoke and foul air, must be large and high. 
 On this account, where there are more than six rooms in 
 the same building, it is better to have two chimneys. It
 
 102 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 thus appears from the foregoing that, by a properly-con- 
 structed aspirating chimney, ventilation may be, under 
 favorable conditions, secured without additional cost for 
 fuel. The attendant unfavorable conditions will be no- 
 ticed presently. 
 
 Cost of the Plenum Movement. Now, to calculate the 
 cost of the plenum movement : If the Eittenger fan be 
 used, and calling its per cent of efficiency 40 the value 
 of x in formula for estimating Hp. (see page 86) we 
 have Hp. = '28 V h (h = height of manometer). In the 
 present example V = 180,000 ; h = *08 (taking the av- 
 
 \ rru TJ -28 X 180, 000 X '08 
 erage). Then Hp. = = 1-1, say one 
 
 horse-power for each room. In practice, it requires from 
 5 to 8 pounds of coal per horse-power per hour, so that 
 the cost of moving the air by mechanical power would be 
 about one third of the cost of heating. 
 
 This estimate is made without reference to recent im- 
 provements which have been made in fans and blowers 
 for moving air more economically. The efficiency of the 
 Blackman fan is doubtless as much as 70 per cent, and, 
 with the Hope water-motor fan, where the water-pressure 
 is as much as 60 pounds to the square inch, the cost would 
 not be more than one third of that of the one above cal- 
 culated. 
 
 It is also important to remember that, in this calcula- 
 tion, enough power has been provided to remove the air 
 independent of the aid of aspirating chimneys. The as- 
 pirating chimney should be considered one of the essential 
 parts of every school-house. It will cost nothing but the 
 first cost of building, except in warm weather, when heat- 
 ing is not necessary ; when, of course, means must be 
 provided to build a fire in it for the sole purpose of cre- 
 ating a draft. The aspirating chimney always serves a
 
 THE COST OF VENTILATION. 103 
 
 good purpose, and, in ordinary conditions, will be suffi- 
 cient for all the purposes of ventilation ; but there will 
 be times when it will not be wholly adequate. In windy 
 weather it is impossible so to regulate the draft that all 
 the rooms of a large building will be ventilated equally. 
 
 Again, it must not be forgotten that the aspirating 
 chimney, drawing as it does the air from the room, is a 
 vacuum-forming process, so that the incidental openings 
 of doors and windows, as well as the crevices around im- 
 perfect fitting ones, necessarily become inlets, thus inter- 
 fering with the draft through the inlets intended to admit 
 the fresh warm air. (Let it be repeated and emphasized 
 here, that in cold climates double windows should be pro- 
 vided. They lessen by one half the amount of heat lost 
 by conduction through them, as well as shut off air-cur- 
 rents where they are not wanted.) 
 
 It becomes evident, then, that in systems now in use 
 the plenum movement is necessary as a supplement to the 
 aspirating chimney. This gives a fullness of air in the 
 room, restoring the balance between internal and external 
 air, made unequal by the aspirating chimney when acting 
 alone. It also establishes the current independent of ac- 
 cidental openings, and prevents interference to draft in 
 windy weather. When thus working with the chimney, 
 the power required is of course much less than when 
 alone doing the whole work of moving the air. It should 
 be under the control of a competent janitor, who could 
 regulate its working to suit existing conditions. 
 
 Considering, then, the plenum movement as a supple- 
 mentary aid, taking advantage of modern improvements 
 in propellers, and supposing the adjustments to be super- 
 vised by one who understands the principles of ventila- 
 tion, there remains no room for doubt as to whether this 
 method of ventilation can be afforded. It not only can
 
 104 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 be afforded, but it should be regarded as indispensable. 
 Nothing is more needed in this age than a general en- 
 lightenment on this subject of ventilation. Ignorance of 
 employes should be no excuse for deferring necessary 
 improvements. The improvements are needed by the 
 public. The public are willing to pay for them, and 
 there are persons competent to make them. When this 
 kind of service is demanded, the supply will follow as 
 a natural consequence. 
 
 CHAPTER XVI. 
 
 WARMING. 
 
 Heat : The Amount needed for Comfort. The degree 
 of temperature most conducive to health is not a con- 
 stant. The temperature varies not only for different in- 
 dividuals but for the same individuals at different times. 
 A youthful, healthy adult, actively employed, will be 
 comfortable at a temperature of 60, while elderly persons 
 or invalids require a temperature of 68 to 75. Children 
 generally require a higher temperature than adults, and 
 this especially when they are bodily inactive, as in the 
 school-room. It is impossible to fix the temperature of a 
 school-room to suit the changing conditions and indi- 
 vidual characteristics of all, but some degree must be 
 maintained which most nearly approximates the average 
 necessities. A temperature of 70 is generally considered 
 the proper degree for school-rooms ; it is probably as 
 nearly correct as any fixed temperature can be. 
 
 The relative humidity of the air has something to do 
 with the temperature which will be most conducive to
 
 WARMING. 105 
 
 comfort. In a moist atmosphere a temperature of 65 
 would probably seem as warm as 70 in a dry atmosphere. 
 It is worthy of remark here that many medical authorities 
 think that the American tendency is to overheat our 
 houses, and that a much lower temperature than that 
 generally maintained would be more healthy. Feeling is, 
 no doubt, the truest guide to the proper temperature. 
 The body should be made comfortable, even if a higher 
 temperature be required than is thought normal. If an 
 individual's circulation is so sluggish as to require a high 
 temperature to maintain comfort, the remedy is not in 
 an immediate deprivation of the heat, but in removing 
 the desire for it by exercise and due attention to the laws 
 of health. 
 
 The Transmission of Heat. Heat is transmitted in 
 three ways by conduction, by radiation, and by convec- 
 tion. By conduction, heat passes through bodies from 
 particle to particle, without any change of relative posi- 
 tion between the particles. Heat applied to one end of a 
 metallic rod passes through its entire length. The facility 
 with which heat passes by conduction depends upon the 
 nature of the medium through which it passes. All sub- 
 stances conduct heat, but some so slowly that they are 
 sometimes called non-conductors. In general, the metals 
 are good conductors, while air, water, and dry vegetable 
 fabrics, such as wood, cotton, etc., are bad conductors. 
 
 The conductivity of bodies usually diminishes as the 
 temperature is raised, though no definite laws of the rate 
 of this decrease have been formulated. This fact becomes 
 important in house-heating, and furnishes another objec- 
 tion to overheating stoves and heaters ; for while in this 
 condition they not only become pervious to poisonous 
 gases, but by their diminished conductivity compel the 
 heat to seek an exit through the chimney instead, of con-
 
 106 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 ducting it into the room. In selecting stoves and heat- 
 ers, due precaution should be exercised on these two im- 
 portant points, thus securing a maximum of heat, and a 
 minimum of escaping gases. Heaters should therefore 
 be large, so as to furnish a large surface moderately 
 heated, instead of a small surface highly heated. They 
 should be lined with fire-clay or brick, to intercept the 
 poisonous carbonic oxide and other gases. By the con- 
 ductivity of iron the heat stored up in steam or hot water 
 is utilized in a room after having been carried some dis- 
 tance from the source of the heat. It will also be a 
 source of great waste if the convey-pipes leading to the 
 several places where heat is wanted are not packed in 
 some non-conducting material, to prevent the escape of 
 heat into places where it is not wanted. 
 
 Radiation. Eadiant heat differs from conducted heat 
 in several ways. While conducted heat requires a sensi- 
 ble medium for its transmission, and a time which is de- 
 termined by the nature of that medium, radiant heat re- 
 quires no such medium, and travels with the velocity of 
 light. Eadiant heat will perhaps be better understood by 
 a few introductory remarks on light, with which radiant 
 heat is probably identical. Without entering into a dis- 
 cussion of radiant energy, it may be said that all experi- 
 mental observation thus far serves to corroborate the 
 theory that light is a mode of molecular motion in a sub- 
 tile medium not cognizable to the senses and permeating 
 all space. It travels at the rate of 185,000 miles per sec- 
 ond. Its effects on life are well known, it being the 
 prime active agent in all vegetable and animal existence. 
 If a beam of solar light be admitted into a darkened room 
 and allowed to pass through a prism, it divides into seven 
 parts, and, if projected on a white wall or screen, it will 
 appear in as many different colors, red, orange, yellow,
 
 WARMING. 107 
 
 green, blue, indigo, and violet, commonly called the solar 
 spectrum. When passing from one medium to another 
 of different density light is bent out of its direct course. 
 This is termed refraction. Now, in the solar spectrum 
 the several parts denoted by the seven colors are refracted 
 at different angles, the red least and the violet most. It 
 is this which makes the light spread out like a fan and 
 appear as a continuous band on the screen. 
 
 These colors, when examined separately, manifest 
 properties somewhat different, though they have many 
 properties in common. The red ray the least refracted 
 shows the greatest heat, and the violet the least. By 
 Xewton's interference disks it is proved that these rays 
 also differ in wave-length, the red being the longest and 
 the violet shortest, but their vibratory rapidity is in- 
 versely as their length. In common, all these rays have 
 the property of reflection, refraction, and polarization. 
 The relevancy of these remarks will now appear. 
 
 If the spectrum be examined, just beyond the red, 
 where it appears dark, it will be found to possess the same 
 characteristics, except visibility, as other parts of the 
 spectrum. The ratio of increasing heat from the violet 
 to the red is continued into the dark part, which is found 
 to be of a higher temperature than any other part. This 
 part may be deflected from its course by a smooth surface, 
 and collected by a lens, showing that it possesses in com- 
 mon with light the properties of reflection and refraction. 
 It differs from light only in being invisible. Its waves 
 are longer and vibratory motion slower than the luminous 
 parts of the spectrum. The waves and vibrations are not 
 of the requisite length and frequency to affect the optic 
 nerve. That is to say, there is nothing in the organ of 
 sight to respond to waves and vibrations of this length 
 and rate. 
 11
 
 108 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 The effect of radiant heat from the sun, both lumi- 
 nous and non-luminous, is well known to all. No arti- 
 ficial heat can take the place of solar heat. The sanitary 
 beneficence of sunshine is proverbial. It is reasonable 
 now to suppose that the form of artificial heat which 
 most nearly resembles solar heat is most healthful. All 
 bodies radiate heat. If two bodies are separated by noth- 
 ing but air, each is constantly receiving heat from the 
 other, but if one is of a higher temperature than the other 
 the hotter body will radiate more than it receives, while 
 the cooler body will radiate less than it receives ; hence, 
 by this process of exchange, the heat of the two bodies 
 will become equalized. The air between the bodies will 
 not be affected by the radiant heat of either, and this is 
 equally true whether the radiant heat is luminous, as 
 from an open fireplace, or non-luminous, as from stoves 
 .or heated pipes. 
 
 Radiant heat is transmitted in straight lines, and, like 
 light, diminishes in intensity as the square of the distance 
 from the source of heat increases. It passes through the 
 air without affecting it, but heats all solid bodies upon 
 which it strikes. Tyndall, by a series of experiments, has 
 concluded that vapor of water in the atmosphere, if in 
 considerable quantity, intercepts the passage of radiant 
 heat, and to such a degree as almost to make a humid air 
 opaque to radiant heat. This, however, has not been 
 verified by other experiments. 
 
 The air of a room heated by radiation can not be ac- 
 curately tested by a thermometer, as the bulb receives 
 radiant heat, while the air surrounding it remains cool. 
 To prevent this, the bulb should be surrounded by a 
 bright piece of tin, to reflect away the radiant heat. 
 
 One advantage of radiant heat is. that it warms the 
 body and the objects in the rooin without heating the air
 
 WARMING. 109 
 
 we breathe. An accompanying disadvantage is that, in 
 ordinary heating by radiation, especially that of the fire- 
 place, the radiant heat can warm but one side of the body 
 at the same time. There is no doubt that if the body 
 could receive sufficient radiant heat to warm it on all 
 sides an atmospheric temperature of 50 would be more 
 healthful than a higher one. 
 
 Radiant heat is believed to possess peculiar sanitary 
 virtues, and we have seen good reasons for this belief. 
 Some writers even express the relative values of con- 
 ducted, radiant, and convected heat by characterizing 
 radiant heat as "golden," conducted heat as "silver," 
 and convected heat as " copper." From the earliest 
 times the open fire has been instinctively felt to possess 
 special virtue. The peculiar exciting glow produced by 
 the fireplace is the common experience of everybody. Its 
 peculiar virtue is not alone in abstracting foul air from 
 the room, but in the nervous stimulus of direct radial 
 contact. 
 
 The relative value of luminous and non-luminous ra- 
 diation is not known, but the>e is little doubt that the 
 former far exceeds the latter. There is reason for this. 
 The luminous heat appeals to one more sense, that of 
 sight, and, even though the physical qualities of the two 
 kinds were otherwise the same, this alone might materially 
 modify the total effect. We always look at the glowing 
 grate, and are never indifferent to it. The direct lumi- 
 nous radiation of a fireplace is the best substitute for sun- 
 shine, and the direct radiation of a heated body is proba- 
 bly next in value. It will be seen, however, in our dis- 
 cussion of combined methods of heating and ventilating, 
 that direct radiation alone is not sufficient. 
 
 Convection. In fluids, such as air and water, the 
 composing particles are free to move among one another,
 
 HO VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 there being no friction or cohesion between them. When 
 any of these particles become heated by contact with a 
 hot body they expand, decrease in density, and rise, other 
 particles moving in to fill their places. The circulation 
 thus caused is termed convection. Convection is not, 
 like radiation, a specific kind of heat, but is simply a 
 mode of heat-conveyance. The particles, when separately 
 considered, are heated by conduction, when they at once, 
 by their diminished specific gravity, rise and give place 
 to others to be heated in the same manner. The process 
 may be likened to a large number of pupils crowded 
 around a stove ; the nearer ones become warm, fall back 
 and give place to the others, till the whole number be- 
 come warmed. It is by convection that air and water are 
 heated. Both of these fluids are poor conductors, and 
 were it not for the lack of cohesion between their parti- 
 cles there would be no hope of warming them. Their 
 non-conducting property may be proved by trying to heat 
 them from the top downward. If ether be poured on the 
 surface of water it may be burned off without affecting 
 the bulb of a thermometer placed half an inch below the 
 surface of the water ; but the same amount of heat ap- 
 plied at the bottom of the containing vessel would sensi- 
 bly raise the temperature of the whole contents. It is 
 evident, then, that air or water must be heated at the 
 bottom. 
 
 To prevent the too rapid escape of heat, warm air is 
 sometimes admitted at the top of the room, and drawn 
 out at the bottom near the floor. This has been tried in 
 some of the European hospitals. As naturally to be ex- 
 pected, this method has not been successful. It is work- 
 ing against the force of gravity instead of with it. If 
 accomplished at all, it must be at the expense of con- 
 siderable power. Hot water can by means of a syringe
 
 METHODS OF WARMING. HI 
 
 be forced to the bottom of a vessel of cold water, thus 
 warming it, but it takes power to do it. The same prin- 
 ciple holds when dealing with air. 
 
 CHAPTER XVII. 
 
 METHODS OF WARMIHG. 
 
 THE various methods of warming school-houses will 
 be considered in connection with their accompanying pos- 
 sibilities of ventilation ; for a system of heating the air 
 which does not at the same time provide for its necessary 
 renewal is hardly worthy of consideration ; such meth- 
 ods, therefore, will be considered only to expose their 
 defects, that they may the sooner give place to better ones. 
 
 The Open Fireplace. The open fire, as a means of 
 heating, is coming to be regarded as an antiquated insti- 
 tution, which very well answered the purpose of our un- 
 learned forefathers, but which is now regarded as too 
 primitive for this age of steam, hot air, and patent stoves. 
 While the open fire still has a limited existence in private 
 dwellings, in the form of ornamental, badly-constructed 
 grates, and dummy mantels, it is no longer even thought 
 of in this country as a means of warming school-houses. 
 It will receive attention here, not as an historical relic, 
 but partly because it is the best arrangement, as far as it 
 goes, for the combined purpose of warming and ventilat- 
 ing that has ever been devised, and partly because the 
 best school-house in the world the City of London High 
 School is so warmed, ventilated, and made comfortable. 
 
 The history of the open fireplace, from its first use by 
 the Romans, need not here be given ; we are interested
 
 112 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 only in that form of it which best conforms to the prin- 
 ciples of heating and ventilating. One of the best con- 
 
 FIG. 16. 
 
 structed fireplaces is Dr. Arnott's smokeless grate, which 
 may be understood by reference to Fig. 16. The chim- 
 ney, rsuw, is of the usual construction ; a b ef repre-
 
 METHODS OF WARMING. 113 
 
 sent the front bars of a bottomless grate, it being open 
 for the admission of coal, and needs to be supplied only 
 once a day. The fire is lighted by laying on the surface of 
 the coal, at ef, a sufficient quantity of light wood to insure 
 ignition. The coal below becomes heated ; the bitumen 
 rises and burns. As the fire burns low, it is raised by 
 means of a lever, h, working in the notched bar I, which 
 pushes up a false bottom s s, upon which the coal rests. 
 The fire is supported by air which passes through the 
 bars in front ; v represents a valve or damper in the wall 
 near the ceiling, and regulates an opening into the chim- 
 ney. This further serves as a ventilator, and may be con- 
 trolled by means of the cord x suspended within easy 
 reach. In ordinary fireplaces the large space above the 
 fire robs the room of much of its pure air, which mixes 
 with the smoke in large quantities and passes up the 
 chimney. This is prevented in the grate now under con- 
 sideration by a device, here described in Dr. Arnott's own 
 words : " The whole of the air so contaminated, and 
 which may be in volume twenty, fifty, or even a hundred 
 times greater than that of the true smoke or burned air, 
 is then all called smoke, and must all be allowed to as- 
 cend away from the room, that none of the true smoke 
 may remain. It is evident, then, that if a cover or hood 
 of metal be placed over a fire, as represented by T in the 
 diagram, or if, which is better, the space over the fire bo 
 equally contracted by brickwork, so as to prevent the 
 diffusion of the true smoke or the entrance of pure air 
 from around to mix with it, except just what is necessary 
 to burn the inflammable gases which arise with the true 
 smoke, there will be a great economy. This is done in 
 the new fireplace, with a saving of from one third to 
 one half of the fuel required to maintain a desired tem- 
 perature. In a room the three dimensions of which are
 
 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 15 feet, 13 feet, and 12 feet, with two large windows, 
 the coal burned to maintain a temperature of 65 in cold 
 winter days has been 18 pounds for 19 hours, or less than 
 a pound an hour." 
 
 The room here supposed has about one fourth the ca- 
 pacity of an ordinary school-room. This fireplace would 
 then, according to Dr. Arnott, warm a school-room with 
 less than 4 pounds of coal per hour. But we found by a 
 previous calculation that about 18 pounds are necessary 
 when the conditions of ventilation are all provided for 
 and the temperature to be raised is 35. It would appear 
 from this great difference that, after making due allow- 
 ance for the four extra windows and for the rigor of our 
 climate over that of England, a form of open fire, such 
 as that just described, is as economical as other modes of 
 heating. 
 
 Heat is further economized in Boyd's open fireplace, 
 by means of which, in addition to Dr. Arnott's plan, the 
 cold fresh air is admitted from the outside to a chamber- 
 box just back of the fire. This being put in communica- 
 tion with the room furnishes an inlet of pure warm air. 
 It is this kind of fireplace which is used in the magnifi- 
 cent high-school building of London, which has only 
 recently been finished. Further provision was made in 
 the construction of this school-house in making foul-air 
 openings near the ceiling and leading to a mammoth as- 
 pirating chimney extending to the basement. For the 
 open fireplaces a separate flue is provided for each room 
 independent of all the others. 
 
 In a climate in which the heat thns supplied is suffi- 
 cient, this plan is about as nearly ideally perfect as can be 
 imagined. Here the room is heated by convection of the 
 ascending warm currents rising from the fire, by that 
 which comes in from behind the grate, and, best of all,
 
 METHODS OF WARMING. 115 
 
 by the direct radiation of live luminous heat direct from 
 the open fire. The fresh air is warmed before entering, 
 without being overheated. The room is ventilated both 
 from the top and from the bottom of the room. The 
 C0 2 , and other respired impurities, always at the top 
 of the room, are drawn off by the aspirating chimney. 
 Other foul colder gases, from the floors and neighboring 
 closets, which may be lurking in the lower strata of the 
 air, are effectually drawn off by the draft of the fireplace. 
 
 Whether this mode of warming would be adequate for 
 the coldest days of an American winter is not known. It 
 has never been tried. But it is safe to presume that it 
 would be sufficient for nine tenths of the time in which a 
 fire is needed. In severe weather it could be supple- 
 mented with steam-pipes, of which more hereafter. 
 
 Stoves. Everybody who reads this book knows what 
 a stove is, hence no general definition need be given. As 
 a means of warming, a stove may be good or bad, according 
 as the principles which should govern warming and ven- 
 tilation are conformed to or violated. As the latter prac- 
 tice is more common, stoves are growing into general dis- 
 favor. 
 
 The necessary conditions governing the selection of a 
 stove are : 1. It must be large, having sufficient surface 
 to warm sufficiently without overheating. The evils of 
 overheating the air have already been referred to in 
 another place, and it may be here emphasized that air 
 coming in contact with a highly-heated surface is ruined 
 for purposes of respiration. The peculiarly disagreeable 
 odor of such air is probably due to a charring of the or- 
 ganic matter contained in the air. The relative humidity 
 of such air is so low that it is rendered not only unfit for 
 respiration but ruinous to all animal tissue with which it 
 comes in contact. 2. A stove should be lined with fire-
 
 116 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 brick, or other similar material, to intercept poisonous 
 gases which would otherwise pass through the heated 
 iron into the room and contaminate the air. 3. It should 
 combine or be accompanied with some efficient means 
 of ventilation. 4. The smoke-pipe should be long, taking 
 a turn around the room so as to economize the heat. 
 
 These requirements being complied with, there is lit- 
 tle objection to the use of stoves. On the contrary, there 
 is much in favor of them. In point of economy it is 
 the cheapest means of warming known. But where the 
 requirements just enumerated are not observed when 
 stoves are small, without lining, often heated to redness, 
 and without means of ventilation they are not only use- 
 less but become engines of destruction. Hundreds of 
 different kinds of stoves are in use, but I shall specify 
 no further than is necessary to illustrate the correct ap- 
 plication of underlying principles. After canvassing the 
 whole ground, I return to Dr. Arnott, who understood 
 principles, and knew how to apply them. Fig. 17 illus- 
 trates the Arnott closed stove, and is thus described by 
 him : " The complete self-regulating stove may indeed 
 be considered as a close stove with an external case, and 
 certain additions and modifications to be described. The 
 dotted lines and the small letters mark the internal stove, 
 and the entire lines the external case or covering. The 
 letters A B C D mark the external case, which prevents 
 the intense heat of the inner stove, a b cd, from damaging 
 the air of the room. F is the regulating valve for ad- 
 mitting the air to feed the fire (see Fig. 4). It may be 
 placed near the ashpit-door, or wherever more convenient. 
 The letters // mark the fire-brick lining of the fire-box 
 or grate, which prevents such cooling of the ignited mass 
 as might interfere with steady combustion. H is a hop- 
 per or receptacle with open mouth below, suspended above
 
 METHODS OF WARMING. 
 
 117 
 
 the fire like a bell, to hold a sufficient charge of coal for 
 twenty-four hours or more, which coal always falls down 
 
 FIG. 17. 
 
 of itself, as that below it in the fire-box is consumed. The 
 hopper may at any time be filled with coal from above 
 through the lid K, of the hopper, and the other lid K' of 
 the outer case. These lids are rendered nearly air-tight 
 by sand-joints ; that is, by their outer edges or circumfer- 
 ence being turned down and made to dip into grooves filled 
 with sand at e e. The burned air or smoke from the fire
 
 118 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 rises up in the space between the hopper and the inner 
 stove-case, to pass away by the internal flue x into the 
 other flue X of the outer case. L is the ash-pit under the 
 fire-bars ; Gr is the ash-pit door, which must be carefully 
 fitted to shut in an air-tight manner by grinding its face 
 or otherwise. The coal is intensely ignited below where 
 the fresh air maintains combustion, but colder gradually 
 as it is further up. Only the coal in the fire-grate below, 
 where the fresh air has access to it through the fire-bars, 
 can be in a state of active combustion." 
 
 This, it will be observed, is the origin of the modern 
 " base-burner," which is a somewhat degenerated modifi- 
 cation. Modern stove-mongers study for ornament rather 
 than utility. 
 
 To be complete as a ventilator, furnishing an abun- 
 dance of pure warmed air, the space between the inner 
 and outer stove-cases should be in connection with the 
 outside air by means of an air-duct, in which there would 
 be found an inflowing current as the air rises in becoming 
 heated. The outer flue X should be open into the room 
 in order that this warmed air may be utilized. This was 
 not the intent of Dr. Arnott, as he supposed the air in 
 contact with the inner case to be vitiated by excessive 
 heating. But the stove could easily be made of such a 
 proportion between the size of the coal-hopper and the 
 weight and surface of iron used in the construction of 
 the cases as, together with the cold-air connection, to pre- 
 vent overheating. 
 
 A very simple, effective, and inexpensive stove is il- 
 lustrated by Fig. 18. F represents a stove of ordinary 
 construction, upon which is placed a large double drum, 
 the outer part, F, of which is in connection with the fire, 
 and conducts away the smoke and waste products through 
 the pipe P. The inside drum A communicates with the
 
 METHODS OF WARMING. 
 
 119 
 
 outside air by the duct D. The size of the drum and the 
 length of the pipe P should be such as to utilize all the 
 
 FIG. 18. 
 
 heat before the chimney is reached. The action is sim- 
 ple. As the air inside the drum becomes heated by the 
 fire-draft aronnd it, it expands, rises, and passes out at B 
 12
 
 120 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 into the room. The partial vacuum thus formed is filled 
 with inflowing cold air through the duct D. If desired, 
 an upper room may be heated by the same fire by extend- 
 ing the pipe P through the ceiling, enlarging it in the 
 room above into a drum of the same construction as the 
 one described. A patent was granted in 1884 to A. M. 
 Hicks and A. Dishman, of Kentucky, for the invention 
 of a stove of similar construction. 
 
 Stoves, while not the best means of warming, may by 
 a little care and attention be made serviceable and eco- 
 nomical. Considering their comparative simplicity and 
 easy adjustment, and the qualifications of the average 
 builder, it is questionable whether it would not in the 
 majority of cases be better to make use of improved stove 
 heating than tamper with those more improved systems, 
 the adjustment and management of which require scien- 
 tific knowledge and technical skill. A fairly good system 
 properly managed is better than a more excellent one in 
 unskillful hands. 
 
 Many forms of open stoves have recently been made, 
 intended to combine the advantages of the closed stove 
 and the open fireplace ; among which may be mentioned 
 the so-called " Baltimore Heater." It consists of an open- 
 front stove set back into a chimney recess resembling the 
 common fireplace. The smoke-pipe extends up through 
 the entire length of the chimney, leaving the space be- 
 tween it and the inside walls of the chimney as a venti- 
 lating flue which may be put in communication with the 
 room. 
 
 TJie Ruttan System. Stoves may be greatly enlarged 
 and placed in a separate apartment, preferably a basement, 
 where they are made to furnish the heat to the various 
 parts of a building by means of communicating tubes. 
 They are, when so situated, sometimes called furnaces.
 
 METHODS OF WARMING. 121 
 
 Many different kinds of furnaces are in use for thus sup- 
 plying rooms with hot air, all having for their object the 
 heating of air and transferring it to the various rooms. 
 Many of these furnaces are constructed with the sole 
 object of heating, no provision being made for ventila- 
 tion. Some of these fulfill their object well, but, as it is 
 not the purpose here to consider the merits of heaters 
 simply as such, they will not be discussed. 
 
 The most which has been accomplished in the way of 
 warming by means of hot air, where ventilation at the 
 same time has not been ignored, has been done by the 
 so-called Ruttan system. This system of heating and 
 ventilating is coming into quite extensive use in Canada 
 and many of the Northern States, where it is receiving 
 many testimonials of approval. 
 
 For some of the excellent features which this system 
 undoubtedly possesses, and for some of the overdrawn esti- 
 mates of its merits made by its friends, its merits and 
 demerits will here be considered. The system combines 
 the patented inventions of Henry Euttan, of Canada ; J. 
 D. Smead, of Toledo, Ohio ; and B. R. Hawley. For 
 heating, the tubular furnace is used, which, on account 
 of the large surface which is thus brought in direct con- 
 tact with the fire, is economical as a consumer, and the 
 large surface which is also subjected to the air makes it 
 effective as a heater. It conforms well to the require- 
 ments of a heater which have already been insisted on 
 under the discussion of stoves. The fire-box, by its con- 
 struction, presents a large surface to the fire and to the 
 air. The surface is further increased by causing the 
 smoke and burned products to pass successively through 
 the tubes. The furnace is set into masonry, into which 
 the cold air is admitted for warming, and passes out at 
 the tubes to the rooms. The method of admitting the 
 
 6
 
 122 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 heated air into the room is embodied in an invention of 
 Mr. Smead, patented by him in 1882. It may be under- 
 stood by reference to Fig. 19, which represents a vertical 
 
 FIG. 19. 
 
 transverse section through the heater and lower part of 
 one of the flues. A represents the building, B the air- 
 flue, C the heating chamber, D the cold-air duct, E the
 
 METHODS OF WARMING. 123 
 
 furnace chamber, F a wall separating the furnace from the 
 flues, G an opening from the furnace into the flue, H the 
 opening from cold-air duct into the flue, I a hinged valve 
 for regulating the relative supply of hot and cold air, J 
 the opening into the room to be warmed, L a hand-knob 
 for raising and lowering the valve I, d a weight to hold 
 the valve in position. The arrows show the direction of 
 the air. The action of this arrangement is as follows: 
 The air in the chamber C becomes heated, rises and passes 
 up the flue M, and into the room through J. The cold 
 air flows in at D to fill the partial vacuum thus made. 
 When the room becomes too warm, the inflowing hot air 
 is mixed with cold air by turning the knob L, which 
 raises the valve I, closing the hot-air passage G and open- 
 ing the cold-air passage B. The height to which this valve 
 is raised regulates the relative size of the hot- and cold- 
 air openings. It will be well at this point to notice that, 
 while the relative size of the hot- and cold-air openings 
 may be thus regulated, it is doubtful whether the same 
 proportions maintain between the hot and cold air pass- 
 ing through them. The quantity of inflowing hot air 
 may undoubtedly be regulated by this valve, by opening 
 and closing it : but how the cold air is to rise and flow in 
 its place is not so clear. Suppose the valve be raised so 
 as to make the size of the hot- and cold-air openings 
 equal, what will then be the action ? The hot air rising 
 through the flue has a vacuum-forming tendency, and it 
 is supposed by the inventor that the cold air at the bottom 
 of the flue will rise up to fill the partial vacuum. This it 
 might do were there not a source of supply by which the 
 vacuum is supplied with less resistance. There is an in- 
 exhaustible supply of hot air coming from the furnace, 
 already possessing a tendency to rise, and half closing the 
 hot-air opening, as in the case supposed, further increases
 
 124: VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 the tension of the hot air thus resisted as it rises from the 
 furnace. Will not, then, this supply of hot air with high 
 tension be sufficient to supply all vacuum which the air 
 rising in the flue will create ? If the cold air will rise 
 under these conditions, it is difficult to see why the cold 
 air of the room into which the warm air enters will not 
 rise along with and be drawn up by it as it passes in at J 
 and rises to the top of the room. 
 
 This is not a case parallel with the aspirating chim- 
 ney, where hot air rising in a shaft will cause cooler air 
 to flow in through openings into it. In this case the 
 partial vacuum has no other adequate source of supply, 
 which we have seen is not the case in the flue under 
 consideration. 
 
 It is not here maintained, however, that this valve is 
 useless ; on the contrary, it may be, under certain con- 
 ditions, very useful. If it be nearly or quite raised, so as 
 to shut off most or all of the hot air, and if there is a 
 good aspirating chimney drawing the foul air from the 
 room which is being supplied, and if the doors and win- 
 dows are carefully closed, then the cold air will rise in 
 this cold-air duct. But it is safe to conclude that all 
 these conditions are necessary. If there is no aspi- 
 rating chimney there will be no vacuum-forming tendency 
 in the room sufficient to cause cold air to rise. If a door 
 or window is opened, the draft in all cold-air ducts imme- 
 diately ceases, as air, like all other moving bodies, seeking 
 the line of least resistance, will come from a source where 
 it is least opposed ; and through an open door or window 
 the resistance by friction is nothing, while in the cold-air 
 flue it is considerable. Here, let it be observed, is another 
 argument for double windows and spring-closing doors. 
 
 In the Kuttan system the foul air is drawn out of the 
 room from the bottom through registers near the floor.
 
 METHODS OF WARMING. 125 
 
 These outlets are placed, when convenient, on the sides 
 of the room opposite the final outlet, so that foul warm 
 air, as it leaves the room, will pass under the floor which 
 it is thus intended to warm. The foul air thus passing 
 from the different rooms is all collected into a foul-air 
 room adjacent to the smoke-chimney, into the bottom 
 of which it communicates by a large opening. 
 
 The theory of the system may be summarized as fol- 
 lows : The air warmed by the furnace rises through the 
 air-flue into the room, where, within convenient reach, a 
 hand-knob is placed for regulation of hot and cold air. 
 The warm air, after its admission, rises to the top of the 
 room which, on being filled from the top downward, 
 presses the cold air down and out of the outlets. The 
 foul air, it is claimed, being " at the bottom," is thus 
 drawn off, and the upper part of the room kept constantly 
 filled with pure warm air. The floor is warmed by the 
 foul air as it passes beneath on its way out. This foul air 
 is kept in motion by the draft of the chimney into which 
 the foul-air room opens. It may be said in favor of this 
 system that it shows throughout a studied effort toward 
 conformity to physical laws, and is therefore a valuable 
 contribution toward the solution of the difficult and all- 
 important problem of ventilation. It is an ingenious 
 system, and is doing comparatively good service. The 
 critical review to which it will now be submitted is in- 
 tended to be in the interest of truth and the public good, 
 and toward suggesting improvements rather than con- 
 demning the system. 
 
 In the first place, considering the large amount of 
 friction which the air necessarily encounters in finding 
 its way out, and the rapid passage of air which is neces- 
 sary to secure proper ventilation, a higher degree of fur- 
 nace heat is necessary than is harmless to the air.
 
 126 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 Again, if the air entered the room at the temperature 
 of comfort, as claimed in the theory, it would be too cold 
 to be endured after having made its circuit to the top of 
 the room and settled down to the point of utilization. 
 
 These two reasons make the overheating of the air 
 unavoidable. We have seen that overheated air is dam- 
 aged for purposes of respiration ; and it is evident that 
 the heat necessary to raise air to a high temperature is 
 nearly all lost, as this surplus heat must pass away through 
 walls and windows in cooling down to the degree of com- 
 fort. 
 
 The origin of this difficulty seems to be in the lack of 
 proper distribution of the air as it enters the room. When 
 the incoming air is all at one place, it will of course rise 
 to the top of the room before it becomes sufficiently 
 vitiated to allow its escape before it has been used. It 
 must therefore be retained, but it can not be retained 
 without placing the outlets below. If the air was prop- 
 erly distributed as it enters, it would be sufficiently viti- 
 ated to be allowed to pass out at the top of the room, on 
 reaching that point, the natural place for its exit. 
 
 The placing of the outlets below is further justified, 
 by the theory of this system, in supposing the vitiated air 
 is at the bottom of the room. The fallacy of this assump- 
 tion is shown in another place, under the consideration of 
 the position of outlets, and need not be repeated here. 
 
 A condition of things may exist, and probably does in 
 this system, where the most of the uudiffused C0 2 occu- 
 pies a position somewhat near the breathing line. If the 
 incoming air is warmer than the breath about 95 it 
 will rise above the breath and prevent its ascent higher 
 than that stratum of air having a temperature of 95. In- 
 stead, therefore, of making a dive for the floor, the re- 
 spired breath, carrying C0 8 and organic matter, will rise
 
 METHODS OF WARMING. 127 
 
 a short distance, and, before passing out of the room, 
 must again cross the breathing line. Now, the shorter 
 the distance between this stratum and the breathing line, 
 the less opportunity for diffusion to take place in time to 
 prevent rebreathing the expired impurities. 
 
 An objection to the arrangement for warming the floor 
 might reasonably be urged in the fact that so large a part 
 of the building is submitted to the contamination of foul 
 air with no provision for cleansing. The walls of a shaft 
 or rooiri in which there exist large quantities of air viti- 
 ated by respiration soon become coated with an offensive 
 and poisonous accumulation of organic matter which, if 
 not removed, is liable to contaminate the entire building, 
 and in case of temporary reversal of the draft, as is some- 
 times sure to take place in warm weather, when little or 
 no fire is required, the air, in passing over this foul mat- 
 ter, becomes unfit for respiration before it reaches the 
 room. All foul-air passages should be accessible to the 
 brush of the janitor. 
 
 One obstacle in the way of this system is the difficulty 
 of managing the average builder. In order that the pos- 
 sibilities of the system may be realized, buildings must 
 be constructed from the beginning with special design for 
 its application. In buildings not specially constructed 
 for this system it is practically worthless, and the same 
 is true in buildings improperly designed for it by design- 
 ers who do not fully understand the principles which the 
 system requires of them to materialize. This is in itself 
 no fault of the system, but is, in the present state of me- 
 chanical service, an inevitable obstacle. 
 
 It is not unfrequent to see school-houses built for this 
 system where the construction ignores the very principles 
 upon which the success of the system mainly depends. 
 In one instance which I now have in mind, and which I
 
 128 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 had excellent opportunities of observing, the foul-air out- 
 lets led to single chimneys for each room, which were 
 closed up solid at the bottom, and unconnected with the 
 smoke-chinmey or other source of heat. The windows 
 were numerous and loosely fitted, which allowed the hot 
 air to pass out at the top of them before it arrived at a 
 point low enough to be utilized. The small dummy aspi- 
 rating chimneys, having little draft, failed in their legiti- 
 mate function of removing the foul air of the room 
 in order to give place to the incoming hot air, which 
 could not otherwise find an entrance sufficient to warm 
 the room. These circumstances admitted of but one 
 result. The hot air, all that could be forced to enter, 
 found a lodgment in the upper part of the rooms, where 
 a temperature of about 200 was maintained, while at the 
 floor it was little above the freezing point. Of course the 
 apparatus had to be taken out. 
 
 In conclusion, it may be said of the Euttan system 
 that, if the requirements of the theory be carefully con- 
 formed to in the construction of the buildings, the win- 
 dows and doors made tight-fitting and kept closed, it 
 will work comparatively well, yet even at its best it has 
 inherent defects which must be recognized and met be- 
 fore it can be received as a perfect system.
 
 STEAM HEATING. 129 
 
 CHAPTER XVIII. 
 
 STEAM HEATING. 
 
 IN heating with steam, water is converted into steam 
 in a boiler heated by a furnace situated in the basement 
 or other convenient locality. The steam is then conveyed 
 by means of pipes to the parts of the building to be 
 warmed. 
 
 It will be seen by a careful reading of the foregoing 
 pages that one of the chief defects in all systems of warm- 
 ing and ventilating so far considered is the inadequate 
 distribution of the warmed air. This is a matter of prime 
 importance. Heat should be furnished not only of the 
 necessary amount, but it should be furnished in such a 
 manner that it can be utilized. 
 
 We have seen that it is impossible thoroughly to do 
 this by stoves and hot-air furnaces in buildings more 
 than one story in height. If our school-houses could be 
 confined to a single story, furnace-warmed air might be 
 used, and perfect ventilation be attained. The English 
 House of Commons is heated by means of furnace- warmed 
 air, on a modified plan of Dr. Reid, and all the required 
 conditions of ventilation and distribution are there com- 
 plied with. But the same results would not be possible 
 in an upper story of a building. 
 
 In this building a hot-air chamber, extending beneath 
 the entire floor, supplies the room with warmed air ad- 
 mitted through a perforated floor. Ventilation is at the 
 top, and the foul-air flues have their opening into an as- 
 pirating chimney. 
 
 In buildings of several stories, containing many rooms, 
 the difficulties of heat distribution without waste are met 
 by the use of steam. This is inevitable from the natural
 
 130 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 properties which steam possesses. A correct popular un- 
 derstanding of these properties would eventually settle 
 the question as to the best method of warming large 
 school-buildings. While these properties are easy of dem- 
 onstration, it is curious what erroneous notions are cur- 
 rent concerning them. 
 
 Of course it can not be expected that the printed ad- 
 vertisements prepared by furnace-heating companies will 
 contain much that is scientifically reliable concerning the 
 peculiar heating advantages of steam ; and while it might 
 be pertinent to ask why they do not remain silent regard- 
 ing that which they either misrepresent or misunder- 
 stand, it may perhaps be excused as a sort of special 
 pleading which has come to be regarded as legitimate in 
 advertising. 
 
 But this is not the only source of published error con- 
 cerning the properties of steam. A single instance will 
 suffice. W. C. Whitford, ex-Superintendent of Public 
 Instruction of Wisconsin, in a book on "Plans and Speci- 
 fications of School-Houses," in referring to steam heat- 
 ing says : "A very considerable percentage of the force 
 derived from the heat applied to the water in generating 
 steam is lost in expanding and driving this steam along 
 the iron pipes or through the radiators. In other words, 
 the heat of the burning fuel appears in part in mechani- 
 cal action and not in temperature." 
 
 That this mechanical action is lost is a somewhat 
 strange doctrine. A few quotations from authors who 
 have given special attention to physical laws will be suffi- 
 cient to stand against this view. 
 
 Gage, in his "Physics," says: "Heat that is con- 
 sumed in liquefying solids and vaporizing liquids is 
 always restored when the reverse change takes place. . . . 
 The fact that steam in condensing generates a large
 
 STEAM HEATING. 131 
 
 amount of heat is turned to practical use in heating 
 buildings by steam." 
 
 William J. Baldwin, a scientific mechanical engineer, 
 in his work on "Steam Heating for Buildings," says : 
 " When a solid becomes a liquid, or a liquid becomes a 
 vapor, heat is absorbed more than was necessary to raise 
 it to the temperature of conversion, and this latent heat 
 does work in the destruction in the force of cohesion and 
 other occult changes which take place, and must be ab- 
 sorbed from some other substance. In the case of steam 
 in a boiler, it comes from the fuel during combustion, 
 and when a pool of water is vaporized in the street, it 
 comes from the sun directly, and from the earth, air, etc., 
 indirectly. When steam or vapor is condensed this same 
 quantity of heat that was received, no matter where, is 
 given off to any substance within its influence, air, water, 
 etc., colder than itself, and it is this property, to convey 
 more heat within ordinary controllable temperatures than 
 any other substance, which makes water and its vapor so 
 valuable." 
 
 These properties of steam may be demonstrated by a 
 simple and interesting experiment : 
 
 An apparatus, consisting of a flask, lamp or Bunsen 
 burner, bent tube, and beaker, is arranged as shown in 
 Fig. 20. Into the flask A pour one ounce of water at 
 32 Fahr., and into the beaker C pour 5 ounces at the 
 same temperature. In a short time the water in A will 
 be converted into steam, which will pass through the tube 
 B and be condensed in the beaker G. Immediately after 
 the total evaporation of the water in A, the water in C 
 will be found by testing to be at a temperature of 212 
 Fahr. By carefully noting the time which elapsed from 
 the first application of the heat till boiling commenced, 
 and also from when boiling commenced till the evapora- 
 13
 
 132 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 tion was completed, it will be found that the latter time 
 is 5^ times the former, that it requires 5^ times as long 
 
 FIG. 20. 
 
 to convert boiling water into steam as it does to raise 
 water from the freezing to the boiling point.* 
 
 Now, these facts teach, first, that, as the application of 
 the heat is constant, 5 times as much of it exists as la- 
 tent heat than exists as sensible heat. During the entire 
 process, neither the boiling water nor the steam acquires 
 a temperature above 212, the boiling-point of water. 
 Second, that this so-called latent heat is really no heat 
 at all, but mechanical energy, into which the sensible 
 
 * To avoid accident in this experiment, the flask should not be al- 
 lowed to boil quite dry, as this would cause a vacuum to be formed in 
 the flask, which would suddenly be filled by a rush of water from the 
 beaker through the tube. To avoid a similar result, the tube should 
 always be raised out of the beaker before the heat is removed, for if the 
 water ceases to boil the steam will cease to be driven oflf, and a vaccuum 
 will result the same as though the flask were allowed to boil dry.
 
 STEAM HEATING. 133 
 
 heat of the flame was converted ; this energy being suffi- 
 cient to overcome the cohesion between the particles of 
 the water and to transfer them against gravity over into 
 the beaker. Third, that as the water in the beaker, con- 
 taining 5 times as much as was evaporated, was raised 
 to a temperature equal to the highest temperature of the 
 steam, this latent heat, in the form of mechanical energy, 
 appears as sensible heat as soon as condensation takes 
 place. Fourth, that during the passage of the steam, 
 through the tube, none of the latent heat is lost ; that 
 its re-appearance as sensible heat is reserved until the in- 
 stant of condensation. 
 
 In view of these principles, practical insight need not 
 be very far-reaching to see the great advantage possessed 
 by steam for the purposes of heating, when heat is to be 
 carried to some distance and distributed. The mechani- 
 cal work necessary to "drive steam through pipes and 
 radiators " exists in the steam itself, for its inherent prop- 
 erty of expansion makes it self-driving. 
 
 If steam-pipes could be perfectly insulated, so as ab- 
 solutely to prevent exchange of temperature between them 
 and the air, heat could be transferred to any distance 
 whatever, and without loss. Perfect insulation is of course 
 impossible, but it may easily be made sufficiently good to 
 render the loss in a single large building practically 
 nothing. 
 
 This has been demonstrated by Mr. Holly, who has 
 extended the system from heating a few buildings to as 
 many hundreds, where the steam is all generated in one 
 place and conveyed through carefully insulated tubes to 
 the several houses. 
 
 The method of insulating the pipes which Mr. Holly 
 used maybe described in the words of his circular : "The 
 pipe is placed in a lathe, and wound about first with as-
 
 134: VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 bestos, followed by hair felting, porous paper, manilla 
 paper, finally thin strips of wood laid on lengthwise, and 
 the whole fastened together by a copper wire wound spi- 
 rally over all. This is thrust into a wooden log, bored to 
 leave an intervening air-chamber between the pipe and 
 the wood, and of sufficient size to leave from three to five 
 inches of wood covering. The elasticity of the wrappings 
 permits the free expansion and contraction of the pipe 
 irrespective of the wooden log, which is securely anchored 
 and made immovable. The whole is placed in a trench a 
 short distance below the surface without regard to frost. 
 At the bottom of the trench is laid an earthen tile drain 
 to carry off any earth moisture, and in order further to 
 insure the continuous dryness of the wooden log inclosing 
 the pipe." , 
 
 Such careful insulation is of course wholly unnecessary 
 in the heating of a single building. This description is 
 given simply as an example in further demonstration of 
 the principles in steam heating. 
 
 Mr. Holly also demonstrated, by a carefully conducted 
 experiment, that steam may be conveyed through 1,600 
 feet of three-inch pipe, with a loss by radiation of only 
 2% per cent. This is sufficient to show that in single 
 buildings, where the risers are about the only pipes from 
 which radiation is not wanted, the loss may be regarded 
 as practically nothing. 
 
 It has already been noticed that steam, when not un- 
 der pressure, has a temperature of only 212, that of boil- 
 ing water. When, however, its free expansion is arrested, 
 its temperature will increase in proportion to the pressure 
 to which it is subjected. It is better, therefore, in order 
 not to overheat the air by contact with superheated iron, 
 to have the pressure as light as possible. Here is another 
 important advantage of steam heating : the air need never
 
 STEAM HEATING. 135 
 
 be overheated if a proper regulation of pressure be ob- 
 served, and a sufficient amount of piping be used to fur- 
 nish the requisite surface for radiation. 
 
 Steam-pipes can be carried to any place in a building 
 where heat is desired. In most other systems of heating 
 the heads of the occupants of a room inevitably occupy 
 a position having a higher temperature than that of the 
 feet. This is exactly the reverse of what it should be. 
 Nothing is more subversive of good circulation than cold 
 feet. On the other hand, if the feet are kept warm, good 
 circulation may comfortably be maintained, even when 
 other parts of the body are subjected to a comparatively 
 low temperature. 
 
 An arrangement of steam-pipes beneath the floor, as 
 hereafter described, would settle the question of cold feet, 
 and remove the necessity of so high a temperature in 
 other parts of the room as is commonly maintained. 
 There remains no question, then, as to the superior fa- 
 cilities of steam for heat distribution. 
 
 Its cost may be figured otherwise than from the above 
 negative consideration of the loss. The latent heat of 
 steam is 960, that is, it requires 960 units of heat to con- 
 vert one pound of boiling water into steam. This is 
 really the amount that is actually realized as heat. The 
 hot water, when first condensed in the pipes, does on its 
 return impart some of its heat to the room, but the same 
 amount will be necessary to raise it again to the boiling- 
 point in the boiler before it can again be utilized. Theo- 
 retically, one pound of coal will furnish heat sufficient to 
 convert 14 pounds of water into steam, but in the average 
 practice only 9 pounds are realized. Then 960 X 9 = 
 8,640 is the number of thermal units which can be real- 
 ized from one pound of coal. 
 
 It was found, when calculating the cost of heating in
 
 136 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 another place, that 142,959 units of heat are necessary to 
 supply the requirements of one average school-room for 
 one hour, where all the demands of warming and venti- 
 lating are rigidly complied with. Now,142,959 -r- 8,640 
 = 16 "66, the number of pounds of coal necessary to sup- 
 ply one room for one hour. In the former calculation it 
 was found that 18'3 pounds was the number required, 
 which shows nearly 2 pounds per hour in favor of steam. 
 
 So far, steam has been treated with sole reference to 
 its warming and distributing facilities. Objection is 
 sometimes made to steam heating that it does not furnish 
 sufficient ventilation. To this it may be answered that 
 the same is true of any method of heating simply as 
 such 
 
 It has already been explained how heating and venti- 
 lating are antagonistic processes, ventilation always being 
 at the expense of heat. In any method of heating venti- 
 lation must be provided for and arranged as an accessory 
 to the heating. No heating apparatus is in itself a venti- 
 lator. Good ventilation is possible with any system of 
 heating, as no ventilation at all frequently accompanies 
 good methods of heating when by themselves considered. 
 
 That poorly ventilated school-houses are sometimes 
 heated by steam is no argument against steam as a method 
 of warming ; nor does it prove that good ventilation is 
 not possible with steam heating. This will soon be made 
 apparent in the consideration of the different methods of 
 steam heating, which are of three kinds, viz., heating by 
 direct radiation, by indirect radiation, and by direct- 
 indirect radiation. Heating with hot water is not well 
 adapted to school-buildings, which are occupied only at 
 intervals. This .method, therefore, while possessing su- 
 perior advantages for warming private dwellings, will not 
 be here considered.
 
 STEAM HEATING. 137 
 
 Direct Radiation. In direct radiation the coils of 
 steam-pipe or radiators are placed within the room to be 
 warmed. They warm the air of the room by radiation 
 and convection, and do precisely the work of a simple 
 stove where heating is alone provided for and ventilation 
 ignored. The single point of superiority of this method 
 over that of the stove is in the comparatively large radi- 
 ating surface and moderate temperature. As a mere 
 heater, where the temperature of the room is alone con- 
 sidered, no method is more effective, but when so used to 
 the neglect of ventilation, heating by direct radiation 
 alone can not be too heartily condemned. 
 
 Enough has already been said concerning the evils of 
 heating the air of a room without provision being made 
 for frequently changing it. It needs only to be noted 
 here that nothing is more certain to produce these evils 
 than direct radiation when used alone. 
 
 This must not be considered as an argument against 
 direct radiation in itself, but by itself ; indeed, it should 
 form a part of every system of steam heating. It is here 
 condemned only when used exclusively. When direct ra- 
 diation is used in association with a good aspirating chim- 
 ney, in which coils of steam-pipe may be placed to give a 
 good draft, and when the radiators are so arranged that 
 the cold air from the inlets will come in around them and 
 be warmed before reaching the occupants of the room, it 
 makes a fairly good arrangement. This is illustrated in 
 Fig. 21, where D is the outside wall ; W, the window ; 
 E, the cold-air duct ; K, the radiator ; A, the ventilating 
 shaft ; B, the upper foul-air vent ; C, the lower foul-air 
 vent. The arrows show the direction of the currents. 
 
 This arrangement is commonly met with in school- 
 houses, and is somewhat better than no provision at all 
 for ventilation, but it is very inadequate. The heat can
 
 138 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 not by this means be properly distributed. If the outlet 
 B is kept open, the warm unused air will escape ; if it is 
 
 FIG. 21. 
 
 kept closed, the foul air will accumulate in the top of the 
 room. The radiator K, while good so far as it goes, does 
 not warm the air sufficiently as it enters to prevent cold 
 drafts, providing the inlets are sufficiently large for the 
 demands of ventilation. 
 
 Steam heating by direct radiation, even without any 
 provision for ventilation other than by windows, is preva- 
 lent, almost discouragingly so. As a single illustration, 
 the following words of John D. Philbrick, in his circular 
 on " City School Systems in the United States," may be 
 used. In speaking of the high-school in the city of "Wash- 
 ington he says : " It is to be regretted that the high-school
 
 STEAM HEATING. 139 
 
 house recently erected in our national capital should be 
 in its planning so far behind the times. Its conspicuous 
 absence of merit was not to have been anticipated, consid- 
 ering the high reputation which the city had acquired for 
 good school-house building in the erection of the Frank- 
 lin and so many other good school buildings. . . . The 
 heating is effected by means of direct steam radiation." 
 
 Washington is here named because of its prominence 
 and the common interests which center there ; but it is 
 not the only city in which blunders have been made, and 
 are being made, in school-house building relative to heat- 
 ing and ventilating. In fact, the taking of Washington 
 as typical is exceeding liberality toward other cities, some 
 of which are really much worse. 
 
 During the summer of 1886 I visited many school- 
 buildings, with a view of studying their provisions for 
 warming and ventilating. Among those which were 
 warmed by direct radiation, several were arranged as rep- 
 resented in Fig. 22, which is here given, as some of these 
 buildings were new and may be supposed to represent the 
 best that has been done in the localities where they were 
 found. The figure shows the interior of a school-room 
 with the two sides nearest the observer removed. R rep- 
 resents the steam-pipes, extending along the sides of the 
 room under the windows. S is a ventilating shaft in the 
 corner of the room opposite the windows, made tight at 
 the bottom, with no provision for heating the air inside 
 of it. V is an outlet about one foot square, from the 
 room into the ventilating shaft, and situated near the 
 floor. No provision is made for air to enter the room ex- 
 cept through the windows. 
 
 The theory of this arrangement is difficult to guess, 
 but the only one which approaches rationality is that the 
 air is expected to rise from the pipes, move along the top
 
 140 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 of the room to the opposite corner, then to dive down to 
 the bottom of the room and crawl up the shaft. This, 
 
 FIG. 22. 
 
 while quite as reasonable as many current ideas concern- 
 ing ventilation, is expecting altogether too much of the 
 air, whose power of moving is passive and not active. 
 
 The air will rise from the pipes to the top of the room. 
 This is the only correct supposition in the above supposed 
 theory. There is nothing to make it descend when it 
 reaches the corner opposite, unless it is colder than the 
 air below it, and what is to make it colder ? It may be 
 at a temperature lower than when it started from the 
 pipes, but it is still of a higher temperature than the air 
 below it, in all parts not directly over the pipes. Hot air 
 constantly rising to the top of an inclosed space will 
 stratify along the highest plane, the warmest occupying 
 the highest level. As the process continues the line of
 
 STEAM EEATING. 141 
 
 demarkation between warm and cold air will descend 
 lower and lower till the floor is reached, provided there is 
 no outlet higher than the floor through which the warm 
 air may escape. But in the present case there is such an 
 opening, for the air is expected to enter at the windows, 
 and where air can flow in when room is made for it within, 
 it can also flow out when room is made for it without. 
 Now, room will always be made for it without, when the 
 windows are on the leeward side of the room. It has 
 been previously explained how wind produces a partial 
 vacuum on the leeward side of buildings or other obstruc- 
 tions. The air inside will, therefore, have a tendency to 
 flow outward on that side unless there is some counter- 
 acting force inside to prevent it, and in the present case 
 there is none. Cross-currents will thus set in, and the 
 windows will be both inlets and outlets. 
 
 If this little foul-air shaft were converted into an as- 
 pirating chimney of sufficient size in which heat could be 
 easily supplied from coils of steam-pipe extended into it, 
 there would be something to counteract this influence of 
 the wind, as well as to furnish an adequate exit for foul 
 air. In short, these little foul-air shafts, when so ar- 
 ranged, are almost useless. They are not quite useless, 
 because in cold weather, when the air is still, there will 
 be a slight upward draft through them, due to the air in 
 them being a little warmer than the outside air, but when 
 the wind is blowing they are liable to become inlets. Di- 
 rect radiation, with no other means than this for venti- 
 lating or preventing cold drafts, is objectionable. The 
 use of direct radiation, when accompanied with other pro- 
 visions, will appear hereafter. 
 
 Indirect Radiation. In indirect radiation the pipes 
 are not placed inside of the room to be warmed, but out- 
 side in an inclosed chamber opening into the room and
 
 142 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 into the outside air. The air in these chambers becomes 
 heated, rises and passes into the room, and is followed 
 by fresh cold air from outside the building. 
 
 It is evident that a room warmed in this manner is neces- 
 sarily partially ventilated, for the warming is not by ra- 
 diation or convection, but from inflowing warm air, which 
 
 FIG. 23. 
 
 must in entering displace an equal amount of air pre- 
 viously in the room. 
 
 This method of warming may be understood by ref- 
 erence to Fig. 23, where a = outside wall of the house ; 
 B = the fresh-air duct ; c the register opening into the 
 room, and E the coils of steam-pipe.
 
 STEAM HEATING. 143 
 
 Indirect radiation should be accompanied with ade- 
 quate means for abstracting the foul air from the room, 
 either in. the form of a good aspirating chimney or a ven- 
 tilating fan. Unless this be done, any form of indirect 
 radiation will fail ; for, as two bodies can not occupy the 
 same space at the same time, the foul air must pass out 
 before fresh air can pass in. A mere outlet into the open 
 air will not generally suffice, for then the air must be 
 pushed out by the air coming in from the radiators, a 
 work which can not thus be adequately performed. 
 
 The position of the radiators in a system of indirect 
 radiation may vary according to local circumstances. 
 Some builders, however, have a rule of placing them in 
 the outside walls, and others in the inside walls near a 
 central fresh-air shaft situated near the center of the 
 building. Mr. Baldwin is of the former class, and gives 
 as a reason for the outside position that, as the windows 
 furnish a constant source of rapid cooling, a current of 
 cold air is always passing down inside the room in front 
 of them, thence along the floor, cooling the feet of the 
 occupants. Placing the radiators in the outside walls 
 under the windows furnishes an upward current of warm 
 air which meets this cold current, thus counteracting it. 
 
 Mr. Briggs, on the other hand, is of the latter class, 
 and gives as reasons for interior locations of radia- 
 tors : That basement piping is thereby saved ; that it 
 obviates danger from freezing of pipes ; that it prevents 
 loss of heat from introduction ducts or flues which run 
 up the outer exposed walls of the building, and that the 
 internal location makes it possible to place the inlets and 
 outlets on the same side of the room, which it is claimed 
 facilitates the bringing down of the warmed air from the 
 top of the room, where it first rises, to the breathing line. 
 
 Each of these plans of locating radiators possesses 
 14
 
 144 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 some advantages over the other, but both are equally at 
 fault on the one thing necessary to make steam heating 
 perfectly successful. Both admit the warm air through 
 a few large openings situated, at the sides of the room, 
 where it at once rises to the top before it is utilized. 
 This, of course, necessitates the placing of the outlets 
 near the floor, in order to retain the warm air till it has 
 cooled sufficiently to descend and be used. The problem 
 of distributing the warm air as it enters is not solved by 
 either of these methods. Until it is solved, until the air 
 can be so admitted that it can be utilized while on its 
 way to the top of the room, so that when arriving there 
 it may be let out at the ceiling, the place where Nature 
 plainly dictates that its exit should be made, instead of 
 trying to force hot air downward ; until this can be ac- 
 complished, steam heating has little advantage in point 
 of ventilation over some other systems. 
 
 CHAPTER XIX. 
 
 AN IDEAL PLAN" FOB WARMING AND VENTILATINQ. 
 
 THE necessary physical conditions of warming and 
 ventilating have now been fairly well discussed. In our 
 investigations of the different plans which have been em- 
 ployed, the merits and demerits of each have been pointed 
 out. While all have some characteristic points of excel- 
 lence, none so far considered are without numerous and 
 serious defects. Thus far no system has been devised 
 that so distributes the air as it enters the room that it 
 may be let out at the top the place which Nature plainly 
 dictates for its exit. No plan has yet been hit upon which
 
 AN IDEAL PLAN FOR WARMING AND VENTILATING. 145 
 
 keeps the feet of the occupants warmer than the head 
 a necessity which the laws of blood-circulation make 
 plainly evident. No system has yet been put in practice 
 which does not at some point oppose the natural laws of 
 ascent and descent. 
 
 A device will now be described which I believe will 
 not only remedy these defects but will comply with all 
 the requirements of ventilation. In order better to esti- 
 mate its value, let us first enumerate the requirements 
 of ventilation. 1. The air must come from a pure source. 
 2. It must be sufficient in quantity. 3. It must be 
 warmed before being admitted into the room. 4. It 
 must not be overheated. 5. It must be distributed as it 
 enters, so that it may be utilized before it reaches the top 
 of the room. 6. In order that this may be possible, it 
 must be admitted through the floor. 7. It must not be 
 entrapped in the top of the room. 8. The ventilation 
 and air-supply must be independent of doors and win- 
 dows. 
 
 A careful study of the following figures will show how 
 this may be accomplished. Fig. 24 shows the interior of 
 a double chimney, with partition and side toward the ob- 
 server removed so as to reveal the parts. B is the floor 
 of afresh-air shaft which constitutes one division of the 
 chimney, as shown by the broken partition wall E Gr. 
 H is the opening into the large tube C, which carries 
 fresh air to the rooms ; X X shows the front of this tube, 
 cut away so as to show the other side. J J are floor- 
 joists. A shows where the fresh-air tube sends off a 
 branch directly under the floor of the first story ; F is 
 the foul-air register, opening from the top of the room 
 into the chimney. J' J' A' and F' show corresponding 
 parts for the second story. A is the floor of the aspirating 
 chimney, which contains the fresh-air tube just described, 
 7
 
 146 VENTILATION AND WARMING OF SCHOOL-BUILDINGS.
 
 AN IDEAL PLAN FOR WARMING AND VENTILATING. 
 
 and also the smoke pipes, P, which come from the fur- 
 nace and extend to the top of the chimney. 
 
 The action of this chimney explained is as follows : 
 This chimney is to perform the work of ventilating and 
 carrying the fresh air to four school-rooms. The large 
 furnace pipe is divided into the several smoke pipes, P, 
 so that the waste heat from the fire may be utilized in 
 heating the air in the chimney, by making the heated 
 radiating surface as large as possible. The air in this 
 part of the chimney, thus heated, rapidly rises and creates 
 a powerful upward draft, making a partial vacuum, which 
 draws the foul air through the foul-air registers F at the 
 top of the room. The smoke-pipes arc extended upward 
 to the top of the chimney, to prevent the possible reflux 
 of smoke which might otherwise occur in windy weather. 
 The heat from these pipes will also be communicated to 
 the fresh-air pipe C ; and the fresh air which it contains, 
 being thus warmed, will rise and pass under the floor 
 through the branch tubes A and A'. It would probably 
 be better to have the fresh-air tubes leading to the sepa- 
 rate rooms independent of one another to avoid inequality 
 of draft. In the figure two rooms are represented as be- 
 ing supplied from one main pipe C, merely for conve- 
 nience of illustration. The air thus rising in the tube C 
 is followed by cold pure air from the fresh-air shaft B 
 through the aperture II. This shaft, being a part of the 
 chimney, extends to the top of the building, and there- 
 fore brings the air from an elevated and pure source. 
 The top of the fresh-air shaft should be several feet be- 
 low the top of the smoke part of the chimney to avoid 
 the drawing down of smoke. 
 
 As we have seen in previous pages, this chimney must 
 be large. There is little danger, under the present ar- 
 rangement of conveying the smoke, of getting it too large.
 
 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 It should, if built for four rooms, have an area of cross- 
 section of at least 64 square feet, making it equivalent to 
 8 feet square. Summarized, a. chimney thus constructed 
 furnishes an outlet for smoke, for foul air, and an inlet 
 for fresh air. The heat in it from the furnace has a ten- 
 dency both to draw the foul air out and the pure air into 
 the rooms, as explained. 
 
 How, now, is the fresh air thus admitted beneath the 
 floor to be warmed and distributed ? This may be un- 
 derstood by reference to Fig. 25. J represents a series of 
 
 FIG. 25. 
 
 floor joists, and J' another series resting upon the first at 
 right angles. This double arrangement is to give sufficient
 
 AN IDEAL PLAN FOR WARMING AND VENTILATING. 149 
 
 room for the various radiating boxes necessary to perfect 
 distribution. The inlet a corresponds to A and A' of Fig. 
 24, and is the opening into the box B, extending along 
 under one side of the room ; are openings or registers, 
 opening from the large box B into smaller radiating boxes 
 b, which extend along under the floor between the upper 
 set of floor-joists ; s s are steam-pipes for further warm- 
 ing the air as it enters. 
 
 The heat from this source gives to the air already in 
 motion another impulse in the same direction, upward 
 through the floor register R, as indicated by the arrows, 
 thus further increasing and securing constancy and steadi- 
 ness of the air movement. 
 
 The air, on thus entering, will be properly warmed, 
 and being admitted at the floor will secure comfort for 
 the feet. There should be a radiating box, b, for every 
 row of desks, to deliver the air through registers situated 
 at frequent intervals along the aisles. The warm air, thus 
 perfectly distributed, as it enters rises toward the ceiling, 
 both by its own specific lightness due to temperature, and 
 by its tendency to fill the vacuum produced at the top of 
 the room from the draft of the aspirating chimney, as 
 explained in Fig. 24. 
 
 Here there can be no uncertainty about the disposition 
 of C0 2 and the organic emanations from skin and lungs. 
 All of these impurities are carried off as fast as formed, 
 both from a tendency which an animal temperature of 
 98 gives them to rise, and the constant stream of rising 
 air into which they are poured. 
 
 Steam-pipes should also be placed in the large radiat- 
 ing box B, to aid both in warming the air and in increas- 
 ing the strength and steadiness of the movement. These 
 boxes should be made of wood and lined with tin. F is 
 the floor of the room. At there should be a damper
 
 150 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 for regulating the draft, and controlled by a lever ex- 
 tending up through the floor. The opening, a, should 
 be large, as the amount of air delivered through it is 
 great. The form and proportion are of course not speci- 
 fied in the figure, which is only intended to make the 
 principle of the movement understood. 
 
 What, now, it may be asked, will prevent the space 
 beneath the floor from filling with dirt through the floor 
 registers ? This is answered in Fig. 26, which represents 
 
 FIG. 26. 
 
 \J 
 
 d i 
 
 d * d t d. ,d 
 
 a cross-section through a portion of the floor, the radiat- 
 ing box, and containing steam -pipes. F shows the 
 floor ; r the connecting box-riser ; b b, the radiating box ; 
 s s s, the steam-pipes ; and II, the lid of the register in 
 the space fitted for it in the floor. 
 
 The peculiar shape of this lid, as represented, will be 
 sufficient to suggest how the dirt is prevented from fall- 
 ing into the box. Everything which falls through the 
 spaces at the top of the lid will be received by the loops 
 at d. The arrows indicate the direction of the air through 
 the numerous holes made in the perpendicular sides of 
 the several loops. Floating dust will have no tendency 
 to enter these holes, because the current of air will pre-
 
 AN IDEAL FLAN FOR WARMING AND VENTILATING. 151 
 
 vent it, being from the direction to drive it away. These 
 lids, made of light castings, will not be expensive, and 
 can be easily raised out and freed from dirt, which from 
 time to time will accumulate in the loops. 
 
 The two sets of floor-joists which this system necessi- 
 tates will incur some additional expense, but this will be 
 slight when the accompanying advantages are considered. 
 The greater space which the double arrangement would 
 require would not necessitate any increase in the height 
 of the building, for it is plain that when rooms are venti- 
 lated as above described, the height of the room is not 
 important. The number of cubic feet of air space for 
 each pupil loses importance as perfect ventilation is ap- 
 proximated. Thousands of people may stand crowded 
 together in the open air and all be provided with pure 
 air. This is simply because the ventilation of Nature is 
 perfect. The heated emanations from the body rise and 
 fresh air comes in from all sides to fill the partial vacuum. 
 This is the method above proposed. The movement of 
 all the air in the room is upward, with ample provision 
 for the supply of plenty of fresh warm air from below. 
 
 Thus far we have considered ventilation with reference 
 to the requirements of winter, or when artificial heat is 
 required to raise the internal temperature of the rooms 
 above that of the outside. In the fall and spring, when 
 no extra heat is needed in the rooms when the internal 
 and external temperatures are nearly equal it is then 
 only necessary to heat the air in the foul-air compartment 
 of the chimney in order to maintain a draft sufficient to 
 abstract the foul air as fast as formed. There are several 
 ways to do this. A stove may be set at the bottom of the 
 chimney, or coils of steam-pipe may extend into it from 
 the boiler. For the system we are considering this is the 
 proper method of heating the chimney in warm weather.
 
 152 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 By means of valves the steam may be shut off from all 
 the radiator pipes, allowing it to pass only through the 
 pipes in the chimney. And, owing to the manner in 
 which the heat of the smoke and the waste products of 
 combustion are utilized, the necessary heat could be by 
 this means most economically produced. 
 
 This heating of the chimney in warm weather should 
 not be neglected. It is commonly supposed that in warm 
 weather, when the windows may be opened, ventilation is 
 easily secured. This is a great mistake. It is easier to 
 ventilate in winter than in summer. In cold weather the 
 inequality of internal and external temperature is in itself 
 a cause of movement, as heretofore explained ; but when 
 the internal and external temperatures are nearly equal, 
 change of position takes place (in the absence of wind) 
 only by diffusion. 
 
 In order to suit the conditions of cool weather, when 
 a little heat is needed, the pipes extending through the ra- 
 diators should be connected in sections, so that steam 
 could be shut off from any number of them as desired. 
 For instance, Fig. 27 shows a main supply pipe, sending 
 off branches which are again subdivided, each sending a 
 pipe to the several radiators. Thus, section A sends one 
 pipe through each radiating box in the building ; section 
 B another, section C another. When only a third of the 
 usual amount of heat is required, all the valves are closed 
 except C, through which steam will then alone be admit- 
 ted. If more heat is needed, open valve B. In coldest 
 weather, open all. For the severest weather, in high lati- 
 tudes, a section should be set apart leading to direct ra- 
 diators placed in the rooms. By skillful management of 
 the details any temperature may be secured and ventila- 
 tion be equally good in all seasons. 
 
 Another advantage which the double set of floor-joists
 
 AN IDEAL PLAN FOR WARMING AND VENTILATING. 153 
 
 secures is in the effectual deadening of sound which 
 the enlarged space would secure. In all school-houses of 
 
 FIG. 27. 
 
 B 
 
 B' 
 
 C' 
 
 RADIATOR BOX 
 
 two or more stories some means of deadening the sound 
 of moving feet, conducted through the floor and ceiling
 
 154 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 to the room below, is absolutely essential. Where this is 
 effectually done, the cost will exceed that of the double 
 joists. This system of warming and ventilating, it ap- 
 pears to me, answers all the requirements of ventilation : 
 1. The air taken from the height of the building is from 
 a pure source. 2. From the large size of the chimney 
 and fresh-air shaft, this air is sufficient in quantity. 3. 
 By the distribution of steam-pipes as described it is 
 warmed before being admitted into the room. 4. By a 
 proper apportionment of these pipes the air need not be 
 overheated. 5. By the numerous small registers distri- 
 bution is perfect. 6. It is through the floor, thus secur- 
 ing the warmth of the feet. 7. It is not entrapped in the 
 upper part of the room, but rapidly hurried away from 
 this point. 8. The inlets and outlets being of ample size, 
 and the velocity of the air sufficient, the ventilation will 
 be independent of doors and windows. 
 
 On the latter point too much stress can not be laid. 
 Open doors and windows, especially in a city, are a source 
 of great annoyance. The rattle of passing vehicles, the 
 din of machinery and steam- whistles, sometimes render it 
 impossible to hear a recitation. In windy weather great 
 clouds of dust from the streets, and smoke from neigh- 
 boring chimneys, pour in through open windows to com- 
 plete the discomfiture of all helpless victims of window 
 ventilation. In winter, where windows are relied upon, 
 currents of icy cold air pour in, endangering the lives of 
 pupils ; while currents of warm air pour out, sometimes 
 before it has been utilized. 
 
 It will doubtless be a surprise to many that the fresh- 
 air shafts and chimneys for foul air need to be so large ; 
 but a careful perusal of the foregoing pages will convince 
 the intelligent reader that there is no help for this if any- 
 thing like perfect ventilation is approximated. Facilities
 
 AN IDEAL PLAN FOR WARMING AND VENTILATING. 155 
 
 for ventilation are to a house what lungs are to an ani- 
 mal. They must be capacious and active, to maintain a 
 healthy and vigorous life. The ventilating and warming 
 apparatus constitute the vital organs of a building, and 
 are therefore of first importance in school-house building. 
 Utility first and ornamental finish last. Where utility 
 and architectural symmetry conflict, the latter should 
 give way to the former. Give us life first and beauty 
 second. However, it need not be supposed that sym- 
 metry is necessarily sacrificed or school-room capacity in- 
 terfered with by the use of these generous chimneys. 
 
 The three essential qualities of a school-house, named 
 in the order of their importance, are utility, simplicity, 
 and beauty. If these qualities are attended to in the or- 
 der here named, all three are possible of attainment ; but 
 if the order be reversed, as is commonly the case, only 
 the first beauty will be attained. 
 
 In a two-story building one chimney should not be 
 required to serve more than four rooms. If three stories, 
 it may supply six rooms. A peculiarity of this system of 
 ventilating is that the higher the building the greater is 
 its efficiency. The reason for this is evident. The draft of 
 a chimney is not only always increased with its height, but 
 in'this case the higher the building the farther the fresh- 
 air tubes will extend upward through the heated air of the 
 aspirating chimney. This not only adds still more power 
 to the draft, by the additional heat given to the ascending 
 fresh air, but this heat is utilized in giving additional 
 warmth to the air before it enters the radiators. 
 
 There are many designs which might be made, where- 
 by all the qualities of a good school-house are secured. 
 An original plan is suggested in Fig. 28, which may be 
 considered the first story either of a two or three story 
 building. If two stories, there will be sixteen rooms ; if 
 15
 
 156 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 PORCH 
 
 
 SCHOOL ROOM 
 
 | 1 
 
 SCHOOL ROOM 
 
 1 1 
 
 II 
 CU. HATS 
 
 1 1 
 
 1 
 
 HATS CL.|B A 
 
 SCHOOL ROOM 
 
 -J 
 
 SCHOOL ROOM 
 
 SIDE ENTRANCE 
 
 _J 
 < 
 
 X 
 
 SIDE ENTRANCE j 
 
 SCHOOL ROOM 
 
 1 
 
 SCHOOL ROOM 
 
 A B 1 CL. HATS 
 
 1 1 
 
 HATS CL.IB A 
 
 " 
 
 L^P" 
 
 SCHOOL ROOM 
 24' X 34' 
 
 . " . 
 
 SCHOOL ROOM 
 24' x 34' 
 
 
 J PORCH 
 
 
 
 
 
 
 
 A. foul air and smoke. 
 
 
 
 R , 
 
 
 
 * res "' Mr "
 
 AN IDEAL PLAN FOR WARMING AND VENTILATING. 157 
 
 three stories, twenty-four rooms. This is as many rooms 
 as will commonly be found necessary in a single building. 
 
 The plan is self-explanatory. The spaces between the 
 rooms serve the purposes of fresh air, foul air, smoke, 
 water-closet, and hat-room. The water-closet adjoins 
 the foul-air part of the chimney. An opening through 
 the dividing wall will effectually ventilate the closet. A 
 is the smoke and foul-air part of the chimney, and B 
 the fresh-air shaft ; the latter communicating with the 
 former, as shown in Fig. 24. The combined chimney 
 and fresh-air shaft should have at least G4 square feet 
 sectional area. It may be made by this plan of almost 
 any size without inconvenience or sacrifice of symmetry. 
 Iron ladders should be secured on the inside of both com- 
 partments of the chimney to facilitate the adjustment and 
 repair of the various pipes. 
 
 One half of this design makes a plan for an eight- 
 room building. Eight rooms is generally preferable to 
 any other number. For this arrangement not only gives 
 unobstructed light on two sides of each room, but more 
 easily meets architectural requirements, and is sufficient 
 to serve the ends of ordinary graded school-work. The 
 large plan is here given to answer the requirements in 
 large and crowded cities where the economy of space re- 
 quires as few buildings as possible, and for high-school 
 buildings where eight rooms are sometimes insufficient to 
 serve the demands of the proper specialization of the 
 various departments. 
 
 Fig. 29 is a plan, illustrating how the same qualities 
 may be secured in a building of 6 or 12 rooms. 
 
 The advantages which these plans secure are : 1. The 
 whole building is perfectly warmed and ventilated. 2. 
 There is light on two sides of each room. 3. The chim- 
 neys are out of the way and do not project into the school-
 
 158 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 rooms. 4. There is plenty of blackboard room on plane 
 surface unbroken by ad jutting chimneys and a multi- 
 plicity of windows. 
 
 Let it be noted here that narrow hat-rooms are gen- 
 
 Fia. 29. 
 
 SCHOOL 
 ROOM 
 
 r -|A|B 
 SCHOOL ROOK l 
 
 SCHOOL 
 ROOM 
 
 -'SCHOOL ROOM 
 
 SCHOOL 
 ROOM 
 
 SCHOOL 
 ROOM 
 
 PORCH 
 
 REFERENCE. 
 
 A. Foul air and 7oi<. 
 
 B. Fresh air.. 
 
 erally a nuisance, and a source of crowding and disorder 
 at dismissal. The halls should be wide, with a stationary 
 hat-rack extending along each side about three feet from 
 the wall. This arrangement gives not only plenty of room 
 for hats and wraps, but makes them accessible. The small 
 hat-rooms in the foregoing plan are given not so much to 
 meet any real necessity for them, as to utilize space which
 
 AN IDEAL PLAN FOR WARMING AND VENTILATING. 15Q 
 
 would otherwise be useless. By using them as merely 
 supplementary to the hall space, crowding in them may 
 be avoided. 
 
 These, it appears to me, are some of the essentials of 
 a school-house. I leave the superficial embellishments to 
 the taste of the architect. Towers, turrets, buttresses, 
 cantilevers, balustrades, consoles, corbels, scrolls, cupolas, 
 pilasters, pendants, paint, and colored glass are of later 
 consideration. These are all useful after the essentials 
 are first secured. They are educative, and should be en- 
 couraged to the full extent of the remaining means for 
 procuring them after the vital organs have been intelli- 
 gently planned and skillfully adjusted. 
 
 NOTE. A patent on this system has been applied for.
 
 APPENDIX. 
 
 BY a long and laborious series of observations with 
 hygrometers and dry- and wet-bulb thermometers, Mr. 
 Glaisher deduced empirically a series of factors which are 
 of inestimable value in testing the humidity of the air by 
 means of the wet and dry bulbs. To use these factors, 
 multiply the difference between the dry and wet bulb 
 readings by the factor which stands opposite the dry bulb 
 temperature, and the product subtracted from the dry 
 bulb temperature will give the dew point. 
 
 Let t = temperature of dew point. 
 
 " t z - " "dry bulb. 
 
 " t 1 -- " "wet bulb. 
 
 " lc = factor. 
 We then have the formula 
 
 t = ?-(?-?)& (1.)
 
 APPENDIX A. 
 GLAISHER'S FACTORS. 
 
 101 
 
 Reading 
 of dry 
 bulb. 
 
 Factor *. 
 
 Reading 
 of dry 
 bulb. 
 
 Factor *. 
 
 Reading 
 of dry 
 bulb. 
 
 Factor *. 
 
 Reading 
 of dry 
 bulb. 
 
 Factor*. 
 
 10 
 
 8-78 
 
 33 
 
 3-01 
 
 66 
 
 1-94 
 
 79 
 
 1-69 
 
 11 
 
 8-78 
 
 34 
 
 2-77 
 
 57 
 
 1-92 
 
 80 
 
 1-68 
 
 12 
 
 8-78 
 
 35 
 
 2-60 
 
 58 
 
 1 90 
 
 81 
 
 1-68 
 
 13 
 
 8-77 
 
 36 
 
 2-50 
 
 59 
 
 1-89 
 
 82 
 
 1-67 
 
 14 
 
 8-76 
 
 37 
 
 2-42 
 
 60 
 
 1-88 
 
 83 
 
 1-67 
 
 15 
 
 8-75 
 
 38 
 
 2-36 
 
 61 
 
 1-87 
 
 84 
 
 1-66 
 
 16 
 
 8-70 
 
 39 
 
 2-32 
 
 62 
 
 1-86 
 
 85 
 
 1-65 
 
 17 
 
 8-62 
 
 40 
 
 2-29 
 
 63 
 
 1-85 
 
 86 
 
 1-65 
 
 18 
 
 8-50 
 
 41 
 
 2-26 
 
 64 
 
 1-83 
 
 87 
 
 1-64 
 
 19 
 
 8-34 
 
 42 
 
 2-23 
 
 65 
 
 1-82 
 
 88 
 
 1-64 
 
 20 
 
 8-14 
 
 43 
 
 2-20 
 
 66 
 
 1-81 
 
 89 
 
 1-63 
 
 21 
 
 7-88 
 
 44 
 
 2-18 
 
 67 
 
 1-80 
 
 90 
 
 1-63 
 
 22 
 
 7-60 
 
 45 
 
 2-16 
 
 68 
 
 1-79 
 
 91 
 
 1-62 
 
 23 
 
 7-28 
 
 46 
 
 2-14 
 
 69 
 
 1-78 
 
 92 
 
 1'62 
 
 24 
 
 6-92 
 
 47 
 
 2-12 
 
 70 
 
 1-77 
 
 93 
 
 1-61 
 
 25 
 
 6-53 
 
 48 
 
 2-10 
 
 71 
 
 1-76 
 
 94 
 
 1-60 
 
 26 
 
 6-08 
 
 49 
 
 2-08 
 
 72 
 
 1-75 
 
 95 
 
 1-60 
 
 27 
 
 5-61 
 
 50 
 
 2-06 
 
 73 
 
 1-74. 
 
 96 
 
 1-69 
 
 28 
 
 5-12 
 
 51 
 
 2-04 
 
 74 
 
 1-73 
 
 97 
 
 1-59 
 
 29 
 
 4-63 
 
 52 
 
 2-02 
 
 75 
 
 1-72 
 
 98 
 
 1-58 
 
 30 
 
 4-15 
 
 53 
 
 2-00 
 
 76 
 
 1-71 
 
 99 
 
 1-58 
 
 31 
 
 3-66 
 
 54 
 
 1-98 
 
 77 
 
 1-70 
 
 100 
 
 1-57 
 
 32 
 
 3-32 
 
 55 
 
 1-96 
 
 78 
 
 1-69 
 
 
 
 The elastic force of vapor of water increases with the 
 temperature. If, then, the elastic force of vapor of water 
 at the temperature of saturation (dew point) be divided 
 by the elastic force of 'vapor at a given temperature, the 
 quotient will express the ratio of humidity to saturation. 
 The following table shows the elastic force of vapor of 
 water, measured in inches of mercury : 
 Let t = temperature of dew point. 
 
 " R = ratio of humidity. 
 
 " p = elastic force of vapor at temperature T. 
 
 " T = temperature of the air. 
 
 " p' = elastic force of vapor at temperature I (dew point). 
 
 = '. (2.) 
 
 P
 
 1G2 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 Tempera- 
 ture of 
 the air. 
 
 v,-S*' 
 
 fe S g 
 8 111 
 
 S*a 
 S 
 
 Tempera- 
 ture of 
 the air. 
 
 q^ 
 
 III! 
 
 z$aa 
 i* 
 
 Tempera- 
 ture of 
 the air. 
 
 M-S 
 
 lill 
 
 O ^^3 0) 
 
 sa 
 
 IS 
 
 N 
 
 C.O ~ 
 
 SsS 
 
 &"> 
 
 Force of 
 vapor in 
 Inches of 
 mercury. 
 
 T 
 
 /> 
 
 yo 
 
 p 
 
 T 
 
 p 
 
 T 
 
 P 
 
 
 
 0-044 
 
 24 
 
 0-129 
 
 48 
 
 0-335 
 
 72 
 
 0-785 
 
 I 
 
 0-046 
 
 25 
 
 0-135 
 
 49 
 
 0-348 
 
 73 
 
 0-812 
 
 2 
 
 0-048 
 
 26 
 
 0-141 
 
 50 
 
 0-361 
 
 74 
 
 0-840 
 
 3 
 
 0-050 
 
 27 
 
 0-147 
 
 51 
 
 0-374 
 
 75 
 
 0-868 
 
 4 
 
 0-052 
 
 28 
 
 0-153 
 
 52 
 
 0-388 
 
 76 
 
 0-887 
 
 5 
 
 0-054 
 
 29 
 
 0-160 
 
 53 
 
 0-403 
 
 77 
 
 0-927 
 
 6 
 
 0-057 
 
 30 
 
 0-167 
 
 54 
 
 0-418 
 
 78 
 
 0-958 
 
 7 
 
 0-060 
 
 31 
 
 0-174 
 
 55 
 
 0-433 
 
 79 
 
 0-990 
 
 8 
 
 0-062 
 
 32 
 
 0-181 
 
 56 
 
 0-449 
 
 80 
 
 1-023 
 
 9 
 
 0-065 
 
 33 
 
 0-188 
 
 57 
 
 0-465 
 
 81 
 
 1-057 
 
 10 
 
 0-068 
 
 31 
 
 0-196 
 
 58 
 
 0-482 
 
 82 
 
 1-092 
 
 11 
 
 0-071 
 
 35 
 
 0-204 
 
 59 
 
 0-500 
 
 83 
 
 1-128 
 
 12 
 
 0-074 
 
 36 
 
 0-212 
 
 60 
 
 0-518 
 
 84 
 
 1-165 
 
 13 
 
 0-078 
 
 37 
 
 0-220 
 
 61 
 
 0-537 
 
 85 
 
 1-203 
 
 14 
 
 0-082 
 
 38 
 
 0-229 
 
 62 
 
 0-556 
 
 86 
 
 1-242 
 
 15 
 
 0-086 
 
 39 
 
 0-238 
 
 63 
 
 0-576 
 
 87 
 
 1-2&2 
 
 16 
 
 0-090 
 
 40 
 
 0-247 
 
 .64 
 
 0-596 
 
 88 
 
 1-323 
 
 17 
 
 0-094 
 
 .41 
 
 0-257 
 
 65 
 
 0-617 
 
 89 
 
 1-566 
 
 18 
 
 0-098 
 
 1 4? 
 
 0-267 
 
 66 
 
 0-639 
 
 90 
 
 1-401 
 
 19 
 
 0-103 
 
 43 
 
 0-277 
 
 67 
 
 0-661 
 
 91 
 
 1-455 
 
 20 
 
 0-108 
 
 44 
 
 0-288 
 
 68 
 
 0-685 
 
 92 
 
 1-501 
 
 21 
 
 0-113 
 
 45 
 
 0-299 
 
 69 
 
 0-708 
 
 93 
 
 1-548 
 
 22 
 
 0-118 
 
 46 
 
 0-311 
 
 70 
 
 0-733 
 
 
 
 23 
 
 0-123 
 
 47 
 
 0-323 
 
 71 
 
 0-759 
 
 
 
 Example 1. Suppose the temperature of the room as 
 indicated by the dry bulb to be 72 ; the temperature of 
 the wet bulb 68. Kequired the temperature of the dew 
 point, and the degree of humidity. In formula (1) t* = 
 72 ; t' = 68 ; k = 1'75 ; then, t = 72 - (72 - 68) 
 1-75; = 47-5. 
 
 In formula (2) p', for 47 '5 = 0-323 ; p, for 72 = 
 
 0-785 : K = - = . -., = -40 (per cent of saturation). 
 p 0-785 
 
 This shows an atmosphere somewhat too dry. The de- 
 grees of difference between the dry and wet bulb readings 
 which should exist in order to conform to any required 
 standard may be shown by the following:
 
 APPENDIX B. 103 
 
 Example 2. If the temperature of the room as shown 
 by the dry-bulb thermometer be 72, what should be the 
 temperature of the wet bulb in order to conform to the 
 provisional standard of humidity given by de Chaumont, 
 73 ? From formula (2) p' = Up - -73 X '785 = '573. 
 The degree in the table corresponding to this number is 
 63. This is the dew point corresponding to our standard. 
 
 v i ,iw/ t+t*lc-t* 63+(l -75X72)- 72 
 From formula (1) t = ! r = v 
 
 K i. < u 
 
 = 66, the number of degrees which should be shown by 
 the wet bulb when the dry bulb shows 72. 
 
 B. 
 
 Aspirating chimneys and ventilating shafts are some- 
 times employed to counteract the force of the wind, to 
 increase the velocity of the flow of air into the room by 
 means of a fire in the chimney, to warm the air before it 
 enters the room, and to draw the air from an elevated 
 source to insure purity. The following, Fig. 30, illus- 
 trates a simple form, sufficiently accurate to illustrate the 
 use of the formulas, though not ideally correct as to the 
 relative position and number of openings. Reference : 
 1, entrance shaft ; 2, horizontal air-ducts ; 3, room ; 4, 
 aspirating chimney ; 5, grate. We have here, in addition 
 to the conditions before given, an acceleration in the ve- 
 locity of the air entering the room due to the aspirating 
 power of the chimney ; increase of temperature in the 
 chimney by fire ; and friction due to the surfaces and 
 angles in the air-passages. The co-efficients of friction 
 used by engineers are as follows : In ducts, 0*024 ; for 
 rough flues, 0*05 ; for brick flues, 0*05 ; for square elbow,
 
 164 VENTFLAflON AND WARMING OF SCHOOL-BUILDINGS. 
 
 1'50 ; for circular elbow, 0'50 ; air passing from a larger 
 to a smaller flue, '50 ; air passing through a wall or plate, 
 
 FIG. 30. 
 
 0*50 ; air passing from a smaller to a larger flue through 
 an opening in the wall, Fig. 31. Eeference : A, A 1 , A 3 
 
 FIG. 31. 
 
 = areas of flues ; / = co-efficient of friction in ducts ; 
 f 1 = co-efficient of friction in elbows ;
 
 APPENDIX B. 165 
 
 a - -60 when A > A 8 , /' = J -^- - 1 I*, 
 
 when A 1 = A 8 < A, f l = j A .. i I*. 
 
 When the angle of a tube, ventilating shaft, or other air- 
 passage is not 90 the conditions of any angle between 
 and 180 may be approximately expressed by the formula : 
 
 1 -4- cos 
 
 . With these new elements, and from the fact 
 a 
 
 that the velocity is inversely proportional to the square 
 root of the friction, and that for similar cross-sections 
 the friction is inversely as the diameter, we have the 
 following, another modification of Montgolfier's for- 
 mula : 
 
 v = 
 
 + et 
 
 where V = velocity of air in feet per second in ducts. 
 e = expansion of air for 1 Fahr., '00203. 
 t = external temperature. 
 1 2 = internal temperature of the chimney. 
 I = length of ducts, including h + 1? + Z 1 + Z 2 . 
 f = co-efficient of friction in ducts. 
 f 1 = co-efficient of friction in elbows. 
 g = acceleration due to gravity = 32*166 feet. 
 d = diameter of ducts. 
 K 1 = height of aspirating chimney. 
 h? = height of entrance chimney. 
 h = total height of chimneys. 
 
 Example. Suppose that & = 100 ; t = 60 ; I = h + 
 A + |> + ? = 80 -f 30 + 8 + 8 = 126 feet ; h = 80 ; / = 
 05 for brick flues ; f 1 for 2 square elbows = 1*5 X 2 = 3 ; 
 d = 3. Then:
 
 166 VENTILATION AND WARMING OF SCHOOL-BUILDINGS 
 
 0303 (loo 60) 
 
 +1)0808x66- 
 
 = 4/' 00303 (loo 60) 2 x aa-ie x so _ 
 
 7- 
 
 ,/-0812 X 5145-6 _ 741^82272 _ 
 
 " riaiS X 6-266 ~ T62 : V59-44 = 7'7 feet 
 
 291 ^ 
 
 per second. This, being the rate at which the air passes out 
 of the room, may also be taken as the rate passing in. It 
 thus appears that where the friction is considerable the 
 aspirating chimney, or other means of accelerating the 
 movement of air, becomes a necessity. 
 
 C. (See page 84.) 
 
 The following formulas, taken from Schumann's 
 " Manual," will be useful in determining the size and 
 construction of the various parts of the fan : 
 Eeference : 
 
 V = volume of air delivered in cubic feet per second. 
 
 h = height of manometer. 
 
 c = velocity of air entering the fan. 
 
 O=. velocity of air leaving the fan. 
 
 r = outer radius of vanes. 
 
 n= inner radius of vanes. 
 
 r a = radius of inlet. 
 
 I = width of vanes. 
 
 a = height of outlet. 
 
 t = distance from vertical radius to point e (see Fig. 14). 
 
 n = number of revolutions per minute. 
 
 p = radius of a circle whose diameter is unity = 3 '141 6. 
 
 /\T 
 , where there is one inlet. 
 cp 
 
 /~^V~ 
 
 r s = i/ - , where there are two inlets. 
 2cp
 
 APPENDIX D. 167 
 
 r 2 
 b = p. , where there is one inlet. 
 
 
 
 b = , where there are two inlets. 
 r 
 
 V 
 
 b = 5 - ; r t = r 2 to 2 r 8 ; 
 2 j9 r t c 
 
 2636 /=- V 
 
 n = - Vh ; a j ; 
 r Jcj ' 
 
 != 0-159 a. 
 
 D. 
 
 CONDUCTING POWEB OF MATEEIALS. 
 
 Value c, being the units of heat transmitted per hour 
 per square foot of a plate 1 inch thick, the two surfaces 
 differing in temperature 1. 
 
 c = 
 
 Copper 515-000 
 
 Iron 233-000 
 
 Zinc 225-000 
 
 Lead 113-000 
 
 Marble, gray, fine grained 28-000 
 
 Marble, white, coarse grained 22 -400 
 
 Stone, calcareous, fine 16*700 
 
 Stone, calcareous, ordinary 13-680 
 
 Glass 6-600 
 
 Brick-work, baked clay 4-830 
 
 Plaster, ordinary 3 -860 
 
 Oak, perpendicular to fibers 1 '700 
 
 Walnut, perpendicular to fibers 0-830 
 
 Pine, perpendicular to fibers 0-748 
 
 Pine, parallel to fibers 1-370 
 
 Walnut, parallel to fibers 1 '400 
 
 16
 
 168 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 C = 
 
 Gutta-percha 1-380 
 
 India-rubber 1 -370 
 
 Brick-dust, sifted 1 -330 
 
 Coke, pulverized 1 -290 
 
 Cork 1-150 
 
 Chalk, in powder 0*869 
 
 Charcoal of wood, powdered 0-636 
 
 Straw, chopped 0-563 
 
 Coal, small sifted 0-547 
 
 Wood-ashes . . . , 0-531 
 
 Mahogany dust 0-523 
 
 Canvas of hemp, new 0-418 
 
 Calico, new 0-402 
 
 Writing-paper, white 0'346 
 
 Cotton or sheep's wool -323 
 
 Eider-down 0-314 
 
 Blotting-paper, gray 0-274 
 
 For double windows, when the glass is not less than 2 
 inches apart, c = 3 -6. 
 
 Stagnant air, c -3. 
 
 E. 
 
 Value of r, being the radiating and absorbing power 
 of bodies, in units of heat per square foot, for a difference 
 of 1 Fahr., from the experiments of Piclet : 
 
 r = 
 
 Silver, silvered copper 0-02657 
 
 Copper 0-03270 
 
 Tin 0-04395 
 
 Zinc and brass, polished 0-04906
 
 APPENDIX F. 169 
 
 Iron, tinned ........................ 0-08585 
 
 Iron, sheet ......................... 0-09200 
 
 Iron, ordinary ____ . .................. 0-56620 
 
 Iron, cast, new ...................... 0*64800 
 
 Iron, sheet and cast, rusted ........... 0*68680 
 
 Lead, sheet ......................... 0-13286 
 
 Glass .............................. 0-59480 
 
 Chalk .............................. 0-67860 
 
 Wood sawdust, fine .................. 0-72150 
 
 Building stones, plaster, wood, brick .. 0-73580 
 Sand, fine .......................... 0-74000 
 
 Calico .............................. 0-74610 
 
 Woolen stuffs ....................... 0-75220 
 
 Silk stuffs, oil paint ................. 0-75830 
 
 Paper .............................. 0-77060 
 
 Lampblack ................ ......... 0-81960 
 
 Water .............................. 1-08530 
 
 Oil. . 1-48000 
 
 F. (See page 87.) 
 
 T7ie Blackmail Fan. My invention is a ventilating- 
 fan, constructed, as fully described hereinafter, so as to 
 rapidly transmit motion to large volumes of air, carrying 
 the same in solid columns without dispersing it or creating 
 back currents. 
 
 In the drawings, Fig. A (see page 87, .Fig. 13) is a near 
 view of a ventilating-fan with my improvements. Fig. B 
 is a section on the line 1, 2, Fig. A. Figs. C to G (Fig. 
 32, page 170) are diagrams illustrating the formation of 
 the blades. Fig. II, a perspective view of a blade and the 
 hub.
 
 170 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 \y FIG. 32. 
 
 ITig.D 
 
 Fig.O 
 
 o
 
 APPENDIX F. 171 
 
 In experimenting with that class of fans used to ptit 
 air in motion for ventilating and other purposes, I ascer- 
 tained that, in ordinary constructions, while volumes of air 
 would be driven forward by the revolution of the fans, other 
 volumes would be thrown off radially, and still others 
 would be thrown backward instead of forward, as desired, 
 creating currents interfering with the free flow of air to 
 the fan. After many experiments I ascertained that by 
 bending each blade outward at the upper end, forming per- 
 ipheral sections, thus compelling the large volumes ordi- 
 narily dissipated in this direction to move directly forward. 
 
 My present invention relates to certain improvements 
 whereby I have succeeded in preventing altogether any 
 back-flow, insuring a forward propulsion of all the air 
 coming within the influence of the wheel. 
 
 In the course of my experiments I ascertained that it 
 was necessary to so construct each blade of the wheel as 
 to draw or deflect outward the air from the forward edge 
 of every portion of the blade, and to set every portion or 
 face of the blade at such an angle that the forward edge 
 at every point would " cut under " the air rather than 
 move it laterally or carry it with the wheel, and that 
 while portions of the blade might be so bent as to throw 
 the air outward, other portions, if not properly shaped, 
 would draw it back, creating counter currents. I found 
 that to prevent such results it was essential to vary the 
 angle and curve of the blade at different points, and that 
 although such angles and curves would be different, ac- 
 cording to the sizes of the wheels and number of blades, 
 there were certain definite and specific proportions and 
 forms common to all, which result in much improved 
 effects, and which I will now specify. 
 
 The hub A of the wheel may be solid, or may consist 
 of disks a a' secured to the shaft B. From the hub ex-
 
 172 VENTILATION AND WARMING OF SCHOOL-BUILDINGS. 
 
 tend radial ribs b, which meet an annular rim c, and 
 said ribs constitute the straight edges of the blade D, the 
 rim c and ribs being all in the same vertical plane x. The 
 diameter of the hub A and the depth of the wheel should, 
 to secure the best results, be about equal to one sixth of 
 the diameter of the wheel, and the ribs or edges b, instead 
 of being radial, should coincide with lines extending from 
 the periphery, through the hub, midway between the axis 
 and periphery of the latter. The blades, instead of being 
 set with their inner ends parallel to the axis, join the hub 
 upon lines y y, crossing the axial line at an angle at the 
 center, and the forward edge of each blade corresponds to 
 a curve which is gradually increased toward the outer 
 end, the edges of all the blades being upon a plane z z, 
 parallel to the plane x x. Thus the forward edge of each 
 blade may be a rib, e, extending from the hub nearly par- 
 allel for a short distance with the rib b, and then curved 
 forward until it nears the periphery, when the curve is 
 sharper, as shown. The body of the blade, between the 
 edges or ribs b, e, is gradually bent at an angle which be- 
 comes more and more obtuse to the axis of the shaft as it 
 approaches the periphery, as shown in fine lines, Fig. C, 
 and is also bent from a perpendicular line, parallel to the 
 edge 5, as it recedes from said line toward the edge e, as 
 shown in dotted lines, Fig. A. At the periphery the 
 blade is bent to form a peripheral section, d, that extends 
 from the blade to the rim c, and has a forward edge, t, 
 parallel to the axis of the shaft. This peripheral section 
 may form part of the blade, or may be a separate piece 
 riveted or otherwise secured thereto. If the blade were 
 bent or hollowed from each end to the center, as shown 
 by the outline, Fig. D, the air collected by the ends of 
 the blade, instead of being carried outward, would be 
 drawn to the center and thrown backward in currents,
 
 APPENDIX F. 173 
 
 interfering with the flow of air to the wheel ; so, if the 
 blade at any point, as at the hub, Fig. E, is too nearly 
 parallel with the axis of the shaft, the air, instead of be- 
 ing sent forward, will be carried round with the wheel, 
 and the effect will not be proportioned to the power ex- 
 pended. By setting the blade at an angle to the axis, as 
 shown in Fig. C, by maintaining the portion near the 
 hub comparatively flat, by bending the body beyond the 
 center, and by giving a sharper curve thereto near the 
 periphery, where it meets the peripheral section, as de- 
 scribed, I have succeeded in preventing any back-flow, 
 and have with comparatively little power imparted move- 
 ment to large volumes of air in one direction, and in 
 nearly solid columns. This effect is increased by setting 
 the blade somewhat tangential to the axis, as described, 
 instead of radially, the outer end thus being pitched for- 
 ward, so as to draw in the air, instead of dispersing it 
 radially. This will be best understood on reference to 
 diagrams Figs. F and G, in which diagram F illustrates 
 a radial blade which throws out the air by its revolution, 
 while diagram G represents a blade set tangentially to 
 the hub, and tending to draw the air toward the latter. 
 It will be evident that the ribs b e may be flanges formed 
 by bending the edges of the blades. 
 
 It is common to set ventilating-fans in openings in 
 walls or frames, which completely surround the periph- 
 eries of the fans and prevent any radial inflow of air. I 
 set my fan back so that the front face will be nearly on the 
 same plane as the inner surface, w, of the wall or frame, 
 as shown, thus permitting a free flow of air to the pe- 
 riphery (see Fig. 13). 
 
 THE END.
 
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 merit as representing the latest and best work of all schools of psycho- 
 logical inquiry. But of equal importance, and what will be prized as a 
 new and most desirable feature of a work on mental science, are the 
 educational applications that are made throughout in separate text and 
 type, so that, with the explication of mental phenomena, there comes at 
 once the application to the art of education." 
 
 Crown 8vo. Price, $3.00. 
 
 Teacher's Hand-Book of Psychology. 
 
 On the Basis of "Outlines of Psychology." By JAMES 
 SULLY, M. A. 
 
 A practical exposition of the elements of Mental Science, with spe- 
 cial applications to the Art of Teaching, designed for the use of Schools, 
 Teachers, Reading Circles, and Students generally. This book is not a 
 mere abridgment of the author's "Outlines," but has been mainly re- 
 written for a more direct educational purpose, and is essentially a new 
 work. It has been heretofore announced as " Elements of Psychology." 
 
 NOTE. No American abridgments or editions of Mr. Sultys works 
 tre authorized except those published by the undersigned. 
 
 12mo, 414 pages. Price, $1.50. 
 
 D. APPLETON & CO., PUBLISHERS, 
 New York, Boston, Chicago, Atlanta, San Francisco.
 
 
 
 THE LIBRARY 
 UNIVERSITY OF CALIFORNIA 
 
 Santa Barbara 
 
 THIS BOOK IS DUE ON THE LAST DATE 
 STAMPED BELOW. 
 
 Series 9482