346 



Prof. Tyndall on the Absorption and 



Peppermint exercised thirty-four times the action of the air. 



Spearmint exercised thirty-eight times the same action. 



Lavender produced thirty- two times the action of the air. 



Wormwood forty-one times the action of the air. 



The following perfumes were obtained from Mr. Atkinson of 

 Bond Street, and examined in this manner. Small squares of 

 dried bibulous paper, all of the same size, were rolled into 

 cylinders about 2 inches in length ; each of these was moistened 

 by an aromatic oil, and introduced into a glass tube between 

 the drying-apparatus and the experimental tube. The latter 

 being first exhausted, was afterwards filled by a current of dry 

 air which had passed over the scented paper. Calling the action 

 of the air which formed the vehicle of the perfumes 1, the fol- 

 lowing absorptions were observed in the respective cases : — 



Table VIT. 



Name of perfume. Absorption. 



Pachouli . 

 Sandal Wood 

 Geranium 

 Oil of Cloves 

 Otto of Roses 

 Bergamot 

 Neroli . . 



30 



32 



33 



33-5 



36-5 



44 



47 



Name of perfume 

 Lavender 

 Lemon . 

 Portugal 

 Thyme . 

 Rosemary 

 Oil of Laurel 

 Cassia . 



Absorption. 

 . 60 

 . 65 

 . 67 

 . 68 

 . 74 

 . 80 



. 109 



It would be interesting to examine the absolute weights of 

 the substances which produced these effects ; but this I suppose 

 is a task which chemistry is unable to accomplish. In compa- 

 rison with the air which carried the odours into the tube, their 

 weight must be almost infinitely small. Still we find that the 

 least energetic in the list ,has thirty times the effect of the air, 

 while the most energetic produces 109 times the same effect. 

 As regards the absorption of radiant heat, the perfume of a 

 flower-bed may be more efficacious than the entire oxygen and 

 nitrogen of the atmosphere above it. 



After each scent had been introduced, a stream of dry air was 

 admitted at one end of the tube, while the pump was worked in 

 connexion with the other. The perfume was thus cleared out 

 until the needle returned to 0°. This was often a long opera- 

 tion, the odours clung with such tenacity to the apparatus. 

 After the zero had been attained in the case of a strong perfume, 

 a few minutes' rest of the pump sufficed to bring the scent from 

 its hiding-places in the crevices and cocks of the apparatus, and 

 almost to restore the original deflection. The quantity of those 

 residues must be left to the imagination to conceive. If they 

 were multiplied by billions they probably would not reach the 

 density of the air. 



