Mr. C. Brooke on the Nature of 'sEther. o33 



siimed for light-motion which is not required for that of heat, since 

 the rapidity of the undulations and their velocity of transmission is 

 so much the same in both? while at the same time the converse 

 permeabilities to light and heat of crystals of alum, and those of dark 

 smoky quartz, present striking examples of the existing yet unknown 

 differences of physical constitution which are met with in the various 

 kinds of matter. 



It may further be remarked that the dynamical theory of electri- 

 city, if tenable, presents additional reasons for denying the necessity 

 of the presence of aether in ordinary matter. For if the molecules of 

 a rod of copper can transmit an electric wave at the rate of at least 

 250,000 miles in a second, why cannot those of a rod of glass trans- 

 mit a wave of light at about three-fourths of that velocity? 



If, then, these premises be established, it must be granted that the 

 presence of aether is not essential to the transmission of any known 

 kind of wave-motion ; and if so, is it not more in accordance with 

 the true spirit of philosophy, in default of positive knowledge, to 

 abandon unhesitatingly the more violent hypothesis, and to adopt 

 provisionally the more reasonable one above suggested ? 



The phenomena of phosphorescence present further evidence 

 of the intimate relations existing between electricity, heat, and 

 light. It has been observed that fluor-spar may be rendered 

 phosphorescent by a very moderate application of heat, but that 

 it will not again phosphoresce under similar circumstances until 

 an electric spark has been repeatedly passed over its surface. 

 Is it not probable that the phosphorescence by heat of the 

 minerals nuor and apatite and ordinary incandescence are simi- 

 lar phenomena, differing only in the temperature (amount of vis 

 viva) at which heat-motion impressed on the molecules of different 

 bodies is imparted as light-motion to the surrounding medium. 



Our ideas of vis viva and its relation to " accumulated work " 

 are inseparably associated with that of gravitation ; is it not, 

 therefore, something like a contradiction in terms to speak of 

 the vis viva of an imponderable body ? But if sether be not sup- 

 posed to be intermingled with palpable matter, then there is no 

 object in attributing to it an exemption from the otherwise uni- 

 versal law of gravitation; and it will then be imperceptible only 

 because it exists beyond our reach. Moreover, as there are no 

 means of limiting the possible amount of molecular displace- 

 ment in a medium so attenuated, an amount of vis viva is con- 

 ceivable sufficient to impart effective motion to indefinitely denser 

 matter ; and thus this denizen of infinity may be assumed capa- 

 ble of executing its divine mission of imparting to material worlds 

 those essentials to corporeal existence, the very main-springs of 

 organic life — light and heat. 



If these things are so, then (in American common parlance) 

 " ?he bottom falls out " of an experiment lately shown at the 

 Royal Institution to demonstrate the presence of sether by the 



