258 TliAXSACTIOyS OF THE AMERICAN IXSTITUTE. 



The last of the conr^tltnents of the air indicated in our table are 

 the vapors with wliich it is charged. These are sometimes pleasant 

 and agreeable, as is the case with the emanations from the great 

 majority of flowers ; but what shall we say of the vile odors from 

 the kitchen and laundry that meet our nostrils as we cross the 

 thresholds of many houses. It has been suggested that on the walls 

 of our apartments there lie concealed tiie impressions of all the 

 ishadows that have fallen on them, and that perhaps we may some 

 day learn how to evolve them, as we now do those that have fallen 

 on a photographic surface. Beautiful as this idea is, there is but 

 small hope of its ever being realized, unless we first seek and dis- 

 <jover the means of exorcising the palpable ghosts of many dinners 

 that cover the walls so thickly that even he who calculated how 

 many angels could dance on the point of a needle would fail to 

 number them. Aroma from fine wines and costly spices, rich and 

 juicy emanations from viands roasted, boiled and baked, odors strong 

 and penetrating from vegetables, delicate and delicious from fruits 

 and flowers. There they all lie blended together, covering and 

 entombing the shadow}' forms that passing figures have cast. The 

 immaterial being lost in the material, who shall attempt their sepa- 

 ration. 



