T. S. Hunt— Celestial Chemistry. 131 
Ether, which term we may apply to the highly attenuated mat- 
ter existing in the interplanetary spaces, being an expansion of 
some or all of these atmospheres, or of the more volatile por- 
tions of them, would thus furnish matter for the transmission 
of the modes of motion which we call light, heat, ete. ;"and pos- 
sibly minute portions of the atmospheres may, by gradual accre- 
tions and subtractions, pass from planet to planet, forming a 
link of material communication between the distant monads of 
the universe.” Subsequently, in his address ds President of 
the British Association for the Advancement of Science, in 
1866, Grove further suggested that this diffused matter may be- 
come a source of solar heat, “inasmuch as the sun may con- 
dense gaseous matter as it travels in space, and so heat may be 
produced.” 
Humboldt, also, in his Cosmos, considers the existence of a 
resisting medium in space, and says “of this impeding ether- 
lal and cosmical matter,” it may be supposed that it is in mo- 
tion, that it gravitates, notwithstanding its great tenuity, that it 
18 Condensed in the vicinity of the great mass of the sun, and 
that it may include exhalations from comets; in which connec- 
tion he quotes from the 42nd proposition of the third book o 
the Principia. He further speaks comprehensively of ‘‘ the va- 
porous matter of the incommensurable regions of space, 
whether, scattered without definite limits, it exists as a cosmical 
ether, or is condensed in nebulous masses and becomes com- 
y ; 
Power with that of terrestrial gases, the density of ‘the ex- 
: : ” 
* Cosmos, Otté’s translation, Harper’s ed., vol. i, pp. 82, 86. 
} Ibid., vol. iii, p. 40. 
Pp. bs. rans, Roy. Soc, Edinburgh, vol. xxi, part 1; and Phil. Mag., 1855, vol. ix, 
