368 



Tables showing the number of Criminal Offenders in England and 

 Wales, in the year 1 854. Fol. — From the Home Office. 



A Collection of Charts published at the Hydrographic Office, Lon- 

 don. — From H. M. Admiralty. 



Monday, 7th April 1856. 



Dr CHRISTISON, Vice-President, in the Chair. 



The following Communications were read : — 



1. On Atmospheric Manoscopy, or on the direct Determina- 

 tion of the Weight of a given bulk of Air with reference to 

 Meteorological Phenomena in general, and to the Etiology 

 of Epidemic Diseases. By Dr Seller. 



The intention of the author in this communication is to recom- 

 mend the daily determination of the weight, by direct means, of some 

 considerable bulk of atmospheric air. This subject has become of 

 interest to medical observers, owing to the belief which has arisen, on 

 hardly sufficient grounds, that during the prevalence of epidemics 

 the air is of greater weight than usual. The late Dr Prout, whose 

 researches on the specific gravity of air give authority to his opinion, 

 was led to conclude, from the greater weight observed to belong to a 

 given bulk of air at the first outbreak of Asiatic cholera in London 

 during the year 1832, that a malarious principle, heavier than the 

 atmosphere itself, was at that time slowly diffusing itself through 

 the atmosphere. Other observers in the succeeding cholera-epidemics 

 have contented themselves with determining the daily weight of a 

 cubic foot of air by calculation from the recorded barometric pressure, 

 temperature, and humidity. The author endeavours to show that 

 this last method does not meet the case. He says that, in order to 

 detect foreign elastic matter in the atmosphere, it is necessary to 

 weigh a certain bulk of air ; for if the foreign matter be lighter than 

 the atmosphere itself, it increases the general pressure, while it ren- 

 ders a given bulk of air lighter than usual ; and though, when heavier 

 than the atmosphere itself, it both increases the general pressure and 

 the weight of a given bulk of air, yet that the former effect may es- 

 cape detection, while the latter is distinct. 



