58 SCIENCE IN SHOUT CHAPTEKS. 



the relative temperature of these will be lower. Will conden- 

 sation of moisture then follow, as Dr. Siemens affirms ? Let us 

 suppose that the air of the room is raised from 30 to 50 by 

 convection purely ; reference to tables based on the researches 

 of Regnault shows that at 32 the quantity of vapor required 

 to saturate the air is sufficient to support a column of 0-182 

 inch of mercury, while at 50 it amounts to 0'361, or nearly 

 double. Thus the air, instead of being in a condition of giving 

 away its moisture to the walls, has become thirsty, or in a con- 

 dition to take moisture away from them if they are at all damp. 

 This is the case whether the walls remain at 32 or are raised 

 to any higher temperature short of that of the air. 



Thus the action of close stoves and of hot surfaces or pipes 

 of any kind is exactly the opposite of that attributed to them 

 by Dr. Siemens. They dry the air, they dry the walls, they 

 dry the ceiling, they dry the furniture and everything else in 

 the house. 



In our climate, especially in the infamous jerry-built houses 

 of suburban London, this is a great advantage. Dr. Siemens 

 states his American experience, and denounces such heating by 

 convection because the close stoves there made him uncomfort- 

 able. This was due to the fact that the winter atmosphere 

 of the United States is very dry, even when at zero. But 

 air, when raised from to 60, acquires about twelve times 

 its original capacity for water. The air thus simply heated is 

 desiccated, and it desiccates everything in contact with it, 

 especially the human body. The lank and shrivelled aspect of 

 the typical Yankee is, I believe, due to this. He is a desic- 

 cated Englishman, and we should all grow like him if our 

 climate were as dry as his.* The great fires that devastate 

 the cities of the United States appear to me to be due to this 

 general desiccation of all building materials, rendering them 

 readily inflammable and the flames difficult of extinction. 



When an undesiccated Englishman, or a German endowed 

 with a wholesome John Bull rotundity, is exposed to this 

 superdried air, he is subjected to an amount of bodily evapora- 

 tion that must be perceptible and unpleasant. The disagreeable 

 sensations experienced by Dr. Siemens in the stove-heated 

 railway cars, etc. were probably due to this. 



* In each of my three visits to America I lost about thirty pounds 

 in weight, which I recovered within a few months of my return to 

 the "home country" (of English speaking nations). EICHAKD A. 

 PEOCTOE. 



