408 FRAGMENTS OF SCIENCE 



layers of each, var3dng in thickness from 0*02 of an inch 

 to 0*27 of an inch. The liquids were enclosed, not in 

 glass vessels, which would have materially modified the 

 incident heat, but between plates of transparent rock-salt, 

 which only slightly affected the radiation. The source of 

 heat throughout these comparative experiments consisted 

 of a platinum wire, raised to incandescence by an electric 

 current of unvarying strength. The quantities of radiant 

 heat absorbed and transmitted by each of the liquids at 

 the respective thicknesses were first determined. The 

 vapors of these liquids were subsequently examined, the 

 quantities of vapor employed being rendered proportional 

 to the quantities of liquid previously traversed by the ra- 

 diant heat. The result was that, for heat from the same 

 source, the order of absorption of liquids and of their 

 vapors proved absolutely the same. There is no known 

 exception to this law; so that, to determine the position 

 of a vapor as an absorber or a radiator, it is only nec- 

 essary to determine the position of its liquid. 



This result proves that the state of aggregation, as far, 

 at all events, as the liquid stage is concerned, is of alto- 

 gether subordinate moment — a conclusion which will prob- 

 ably prove to be of cardinal importance in molecular 

 physics. On one important and contested point it has 

 a special bearing. If the position of a liquid as an ab- 

 sorber and radiator determine that of its vapor, the posi- 

 tion of water fixes that of aqueous vapor. Water has 

 been compared with other liquids in a multitude of ex- 

 periments, and it has been found, both as a radiant and 

 as an absorbent, to transcend them all. Thus, for exam- 

 ple, a layer of bisulphide of carbon 0*02 of an inch in 

 thickness absorbs 6 per cent and allows 94 per cent of 



