K. DOMESTIC AND HOUSEHOLD ECONOMY. 495 



drink is taken. While the permeability of the earth to wa- 

 ter is generally noticed, the penetration of air to a great 

 depth is overlooked, and also the fact that this stratum of 

 the aerial ocean has its slow insensible currents, just as that 

 in the walls of buildings, in clothing, etc. A bird in a glass 

 vessel closed with a layer of earth can live for hours ; a cur- 

 rent of air can easily be blown through a tube a yard long 

 filled W'ith earth, etc. This air in the earth can be put in 

 motion by differences of temperature as well as by currents 

 of air. Thus the odor of gas has been found in houses with- 

 out gas-pipes, and persons have been injured by it, the gas 

 being drawn from very distant defective pipes in the winter 

 by differences of temperature, since when the room Avas not 

 heated the odor disappeared, and was found in an adjoining 

 heated room. It seems, therefore, that the frozen earth was 

 also penetrable to the gas. This movement of air in the soil 

 renders animal life, though of a low type, possible at great 

 depths ; and to this life must be ascribed the excess of car- 

 bonic acid in the air of the soil, and, at times, its. noxious 

 properties. Accurate investigations show" that the air in the 

 soil of Dresden contains twice as much carbonic acid as that 

 of Munich. This is a subject that demands more attention, 

 on account of its hygienic relations, than it has received. A 

 careless neighbor can render the air of the soil impure as well 

 as its w^ater, and thus contribute to disease. 8 6", May 15, 

 1873, 135, 143, 160. 



CHEAP SUBSTITUTE FOR DOUBLE WINDOWS. 



It is suggested by Dr. Oidtmann, in a pamphlet on the 

 care of health, simply to add a second set of panes of glass, 

 set in an inner rabbet, to a single sash, and thus inclose a 

 stratum of dry air, about 0.2 to 0.4 of an inch thick. The 

 excess of cost, it is said, Avill be more than covered by the 

 economy of fuel in winter ; and at 90, in summer, a room 

 thus protected will remain nine degrees cooler than Avhen 

 supplied with ordinary windows. The plan is also advanta- 

 geous for hot-beds, etc. A good liard quality of glass, that 

 does not become dull by decomposition, must be selected, es- 

 pecially for a southern exposure, since the interior faces can 

 not be cleaned. It is necessary also not only that the glass 

 should be perfectly polished, and not be soiled in putting it 



