300 ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 



ground, the generation of gases in the viscous fluids and in the earth 

 below them, the bursting of countless small bubbles and films, the 

 development of electricity in the evaporation of an impure liquid, the 

 repulsion of small particles by a warm evaporating surface, all help to 

 carry into the lower air a large quantity of microscopic and ultra- 

 microscopic dust. In a research made by the present writer into the 

 diathermancy of thin films of water 1 he was much struck by the force 

 with which the thinnest film snapped; a slightly soapy film of lh inches 

 diameter and about one-millionth of an inch in thickness broke with 

 an audible sound. In the viscous fluid of drying marshes there must 

 be millions of thin films breaking and throwing their minute spray 

 into the air which carries off the contained organic particles. More- 

 over, there must be a continual evolution of very small bubbles of gas 

 from the muddy earth through the liquid above it. The scattering 

 force of small bubbles is surprising. If a glass of effervescing water 

 be watched, the minute bubbles which rise to the surface of the liquid 

 will be seen to throw particles of water to a height of several inches in 

 the air. The smell of drying marshes probably proceeds not only from 

 gases, but from particulate products. Indeed, many organisms and 

 vegetable and animal debris have been actually observed microscop- 

 ically in the air above marshes. Many living germs are probably 

 beyond the range of visibility. The manner in which spores are scat- 

 tered from the hyphse of molds, etc., may represent a similar process 

 in the ejection from marshy surfaces of various microorganisms. The 

 formation of gas bubbles by the Bacillus coli communis may be only 

 one example out of many in which such action takes place. This 

 characteristic of coli communis has been used by Klein as a mark of 

 differentiation between it and the bacillus of typhoid. 2 



The influences, or some of them, which have been named as helping 

 to carry small organic particles into the air over marshes may be capa- 

 ble of launching infective matter from the lungs and air passages of 

 persons suffering from such diseases as scarlet fever, measles, diphthe- 

 ria, and consumption. Certainly organic matter and living particles 

 have been observed in the condensed vapor of breath. Thus walls on 

 which the breath condenses may become culture grounds for disease 

 germs which it contains. 



PERMEATION OF BUILDING MATERIALS BY AIR AND VAPOR. 



The ordinary materials used for floors of dwelling houses are quite 

 ineffectual to prevent the permeation of gases and microorganisms 

 from the soil into the air of the dwelling. By experiments made with 

 several different materials used for flooring, with a view to determine 

 the rate at which air would pass through them into the Torricellian 



■Proc. Brit. Association, Cardiff, 1881. Abstract. 



2 Journal of Pathology and Bacteriology, November, 1893 ; Centralblatt fiir Bakt. 

 and Parasit., A A ol XV, Nos. 8 and 9. Local Government Board Reports, 1892-93. 



