514 Dr. P. F. Frankland. [June 10, 



Fia. 3. 



General Scope of the Experiments. 



A number of experiments have been made on the roof of the 

 Science Schools, South Kensington Museum, with the view of 

 ascertaining the influence of season and atmospheric conditions 

 generally upon the abundance of micro-organisms. This position is 

 well fitted for observations of the kind, the roof being about 50 or 

 60 feet above the surface of the ground, and thus removed from 

 local and accidental influences^ 



A series of experiments was carried out with a view of ascer- 

 taining the relative abundance of micro-organisms at different alti- 

 tudes in towns. These comparisons were effected by collecting 

 samples of air at different elevations on the spire of Norwich 

 Cathedral, on the dome of St. Paul's in London, and on Primrose 

 Hill. Comparative experiments have also been made in the country, 

 as well as in buildings such as museums, hospitals, &c. 



The results obtained in the tube experiments are calculated to the 

 number of micro-organisms contained in 10 litres of air, whilst the 

 results yielded by the exposure of the gelatine-dishes are stated so as 

 to represent the number of micro-organisms falling on 1 square foot 

 in one minute. The conditions under which the experiments were 

 performed are also recorded. 



