Maech 3, 1911] 



SCIENCE 



327 



or next to open windows. These two men 

 think that we ought to do away with all 

 systems of ventilation and use simply natural 

 ventilation — open windows. On the other 

 hand, Dr. Leonard HiU writes me as follows: 



I have not published in extenso my researches 

 on ventilation and have only communicated the 

 general drift of them to the Institution of Heat- 

 ing and Ventilating Engineers over here, in whose 

 transactions my remarks appear. 



The whole point of my work is to force atten- 

 tion to the need of cool air of average humidity. 

 It is not the actual percentage of Oz or COj that 

 matters, but the temperature, the humidity and 

 the movement of the air in houses, schools, etc. 



I visited yesterday a London County council 

 school in which is installed a Plenum system 

 with separate shaft to each school room, giving 

 a moving air at 67-60° Fahrenheit and about 70 

 per cent, relative humidity. All windows and 

 doors are kept closed. The result is admirable; 

 lively, attentive children (at 4 p.m.) and masters 

 looking fresh; no smell of human beings — this 

 was only noticeable when one stood actually 

 among the boys, not in the free spaces of the 

 schoolroom. The headmaster has had hardly any 

 zymotic disease, and in every respect reports bet- 

 ter conditions than in neighboring schools with 

 no such efficient system. The children are re- 

 ported to eat more after coming to school. 



We know definitely that the difference be- 

 tween good and bad air does not consist 

 primarily or to any great extent in variations 

 of oxygen or carbon dioxide, and that there is 

 no such thing as a subtle human poison 

 (anthropotoxin) which varies in proportion 

 to the CO,. 



We have tables which show the different 

 temperatures and how air at, say, 32 degrees, 

 with adequate relative humidity, becomes, 

 when raised in temperature to, say 70 degrees, 

 air practically without moisture. It appears 

 that one of two things must have happened — 

 either the heat must have contracted the ex- 

 isting moisture or the capacity of the air for 

 moisture has been vastly increased by the rise 

 in temperature. 



Practically all of the best manuals of the 

 heating and ventilating engineers tell us that 

 with a good system of ventilation the opening 

 of windows causes only danger; yet, as a mat- 



ter of fact, children in rooms so treated do not 

 exhibit the distressing conditions referred to 

 at the beginning of this letter. 



I have already secured and digested all of 

 the literature to which reference is made in 

 exhaustive bibliographies, indices, and the 

 like, on the subject of air, changes in oxygen, 

 CO,, and so on, as well as the literature cov- 

 ering the relations of the vaso-motor system 

 to the emotions on the one hand, and to skin 

 circulation on the other. 



I believe that the larger part of the question 

 as to why vitality is decreased indoors can be 

 answered through the correlation of these 

 facts, which I already have. There are, how- 

 ever, certain facts which I have not, and 

 which, so far as I have been able to find out, 

 no one has studied. I am not a physicist, and 

 do not know — neither do I know whether the 

 physicists know—the reason why raising the 

 temperature of air increases its capacity for 

 water — in fact, its thirst for water. 



I am writing to ask if any of the readers of 

 Science know of any experiments which will 

 throw any real light on the following ques- 

 tions. 



Is there any difference between steam and 

 humidity? Does steam act strictly in accord- 

 ance with the ordinary laws governing the 

 movement of gases ? Does humidity in the air 

 act exactly as steam does? I suspect that it 

 does not, because heat causes steam to ex- 

 pand, whereas, when we raise the temperature 

 of the air its capacity for moisture becomes 

 vastly increased, which shows either that the 

 steam has contracted or that the air has been 

 altered in such a way as to permit of its ab- 

 sorbing a larger percentage of moisture than 

 it did before. 



I confess to a feeling of hesitation in pre- 

 senting questions which must seem so elemen- 

 tary to your readers, yet when I presented to 

 the American Society of Heating and Venti- 

 lating Engineers' some of the facts that we 

 have recently discovered about the ventilation 

 of school rooms in relation to the physical and 

 mental condition of children they said that I 



' Heating and Ventilating Magazine, February, 

 1911. 



