42 FRAGMENTS OF SCIENCE. 
Bisulphide of carbon is the most transparent vapor in 
this list; and acetic ether the most opaque; one-sixtieth of an 
atmosphere of the former, however, produces 47 times the 
effect of a whole atmosphere of air, while one-sixtieth of an 
atmosphere of the latter produces 612 times the effect of a 
whole atmosphere of air. Seducing dry air to the pressure 
of the acetic 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 
current 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 
Attar of roses 37 
Bergamot 44 
Neroli 47 
Lavender .'....!...........!. 60 
Lemon 65 
Portugal ............... J. 67 
Thyme 68 
Kosemary 74 
Oil of laurel ' ' ' ' 80 
Camomile flowers 87 
Ca??ia-..- '.'.."". 109 
Spikenard 355 
Amseed 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 
lavender 60, that of rosemary 74, while that of aniseed 
