94 Dr Stark on the Influence of Colour mi Odours. 



brown^ orange red, yellow^ and white, they had gained in weight, 

 after exposure to the vapour of camphor. 



After lying in the apartment for twenty-four hours, the cards 

 were again carefully weighed, when the camphor remaining was 

 found to be, in the 



Hence in the same space of time the loss in each was blue ^ ; 

 brown li; red ^l ; yellow ^l ; white -^ 



The influence of coloured surfaces upon the absorption and 

 emission of odours, having, I trust, been satisfactorily shewn, it 

 only remains to state shortly some of the practical conclusions 

 which may be drawn from the experiments detailed. 



If it be thus certain that odorous emanations have not only 

 a particular affinity for different substances, but that the colour 

 of these substances materially affects their absorbing or radiating 

 quality, the knowledge of these facts may afford useful hints 

 for the preservation of the general health during the prevalence 

 of contagious diseases. From their minute division and vast 

 range of action, latent poisonous exhalations or effluvia, inap- 

 preciable by the balance, may no doubt exist to a dangerous 

 extent, without being evident to the sense of smell. But in most 

 cases it will be found, that, when contagious diseases prevail to 

 such extent, the emanations from the sick will, if attended to, give 

 the surest indications of the contamination of the surrounding 

 air. Besides, even if we allow that infectious emanations have no 

 necessary connexion with odours, the preceding experiments will 

 aflPord the strongest possible presumption, that the emanations 

 of an infectious nature, in common with odours, vapours, and 



