194 FRAGMENTS OF SCIENCE. 



ether here employed, and comparing them then together, 

 the quantity of wave-motion intercepted by the ether would 

 be many thousand times that intercepted by the air. 



Any one of these vapors discharged into the free atmos- 

 phere, in front of a body emitting obscure rays, intercepts 

 more or less of the radiation. A similar effect is produced 

 by perfumes diffused in the air, though their attenuation is 

 known to be almost infinite. Carrying, for example, a cur- 

 rent of dry air over bibulous paper moistened by patchouli, 

 the scent taken up by the current absorbs 30 times the 

 quantity of heat intercepted by the air which carries it ; 

 and yet patchouli acts more feebly on radiant heat than 

 any other perfume yet examined. Here follow the results 

 obtained with various essential oils, the odor, in each case, 

 being carried by a current of dry air into the tube already 

 employed for gases and vapors : 



Name of perfume. Absorption. 



Patchouli 30 



Sandal-wood 32 



Geranium 33 



Oil of cloves 34 



Otto of roses 37 



Bergamot 44 



Neroli 47 



Lavender 60 



Lemon 65 



Portugal 67 



Thyme 68 



Rosemary 74 



Oil of laurel 80 



Camomile-flowers 87 



Cassia 109 



Spikenard 355 



Aniseseed 372 



Thus the absorption by a tube full of dry air being 1, 

 that of the odor of patchouli diffused in it is 30, that of 



