560 



various gases were thus determined, and they were found to go 

 strictly hand in hand with the dynamic radiation. 



In the case of vapours the following method was pursued. A 

 quantity of the vapour sufficient to depress the mercury column 0*5 

 of an inch was admitted into the tube, and this was heated dyna- 

 mically by allowing dry air to enter until the tube was filled. The 

 radiation of the vapours thus determined followed exactly the same 

 order as the absorption which had already been measured. The 

 dynamic absorption of the vapour was obtained by pumping out 

 in the manner just described, and it was found to follow the same 

 order as the dynamic radiation. In these experiments the air bore 

 the same relationship to the vapour that a polished silver surface 

 does to a coat of varnish laid over it. Neither the silver nor the 

 air, both of which are elements, or mixtures of elements, possesses the 

 power of agitating in any marked degree the luminiferous ether. 

 But the motion of the silver being communicated to the varnish and 

 the motion of the air being communicated to the vapour, molecules are 

 agitated which have the power of disturbing in a very considerable 

 degree the ether in which they swing. 



The author shows, by strict experiments, that the dynamic radiation 

 of an amount of boracic ether vapour possessing a tension of only 

 i o 1 2 5 ] o o o o o tk of an atmosphere is easily measurable. He also shows, 

 and explains the fact, that with a tube 33 inches long the dynamic radi- 

 ation of acetic ether considerably exceeds that of olefiant gas, while in 

 a tube 3 inches long the dynamic radiation of olefiant gas considerably 

 exceeds that of the ether. Aqueous vapour has been subjected to a 

 special examination, and the author finds it a common fact for the 

 aqueous vapour contained in the atmosphere to exercise 60 times 

 the absorption of the air itself. In fact, the further he has pursued 

 his attempts to obtain perfectly pure and dry air, the more has the 

 air approached the character of a vacuum. The author further points 

 to the possibility of determining the temperature of space by direct 

 experiment. 



Scents of various kinds have been examined. Dry air was passed 

 over bibulous paper moistened by the essential oils and carried into 

 the experimental tube. Small as the amount of matter here entering 

 the tube is known to be, it was found that the absorption by those 

 odours of radiant heat varies from 30 times to 372 times that of the air 



