TRANSACTIONS OF SECTION D. 



705 



The number of organisms falling on a given area has been determined by expos- 

 ing for a definite time small glass dishes filled with sterile nutrient gelatine. 



The greater part of the experiments have been made on the roof of the Science 

 Schools, South Kensington, whilst comparative determinations have been made in 

 various places both in town and country. 



A number of experiments were made with a view to determining the eff'ect of 

 altitude upon the abundance of microbes in the air. These experiments were 

 carried out at various stages on the dome of St. Paul's and on the spire of Norwich 

 Cathedi-al. The air in buildings has also been submitted to examination, and the 

 fact established that, whilst in enclosed spaces in which the air is at rest the num- 

 ber of microbes in suspension may be very small, yet when aerial disturbance is 

 occasioned, e.g., by persons moving about, the number is enormously increased. 



Some oithe more important results are summarised in the following table : — 



The figures given in the above table show that the air on the roof of the Science 

 Schools IS very considerably richer in micro-organisms than that collected in the 

 London parks, and this again than that of the country. 



The gradual attenuation of the microbes in ascending St. Paul's and the spire 

 of Norwich Cathedral is also very striking. 



The figures obtained in the museums, railway carriage, and Hospital for 

 Consumption speak for themselves, and show how in confined spaces the number 

 of micro-organisms present in the air is influenced by the number of persons 

 moving about. 



1886. 2 2 



