THE MICROBIOLOGY OF THE ATMOSPHERE 



PAGE 



19. Diurnal periodicity of total numbers of bacteria in air at the Observa- 



toire Montsouris, Paris, based on hourly readings between March 

 1882 and September 1884 . . . . . . .112 



20. Mean diurnal periodicity curves of thirteen spore-groups expressed 



as percentage of the peak geometric mean concentration. From 

 Hirst trap records at Rothamsted Experimental Station, summer 

 1952 .......... 118 



21. Diurnal periodicity o( Cladosporium at London (South Kensington) 



and Harpenden (Rothamsted), based on Hirst trap catches from 

 May to September, 1954 . . . . . . .121 



22. Exponential form of the die-away of bacteria-carr}ang particles from 



the air of a room. Line A : In an observation military canteen after 

 the occupants had left suddenly. Line B : Observations on the die- 

 away following a group of sneezes in a small room . . -156 



23. Diagram showing changes of circulation in a room according to 



relative temperature of walls and of inside air . . -157 



24. Fraction of spore-cloud remaining airborne (allowing for loss of 



spores from spore-cloud bv deposition to ground), expressed as 



ax/Qo . . . " . . . . . . .171 



25 to 27. Dilution of spore-cloud by eddy diffusion. For m = 175 

 (also m = 1-24 and 2-0), expressed as logarithms of d, dw, diw, D 

 (and also for daw with width of 100 metres) 



25. Deposition coefficient, p = 005 ..... 173 



26. Deposition coefficient, p = 001 ..... 174 



27. Deposition coefficient, p = o-ooi ..... 175 

 28. Infection gradients of potato late-blight {Phytophthora infestans) 



observed by Waggoner (1952) at Clear Lake, Iowa, compared 

 with theoretical line for deposition downwind from a point source 177 



Xll 



