352 Mr Milne's Prize Essay on Comets. 



which we often experience on our own globe, the progress from one 

 degree of temperature to another, as the comet journeys onward in its 

 course, may be little perceived by its inhabitants. 



" It is true that the atmosphere respired by these beings, while it is 

 at one place a highly attenuated gas, is at another converted into a me- 

 dium extremely dense ; and therefore it may be difficult to conceive 

 how animation can be supported in these opposite situations. But 

 when Halley was able to breathe freely in a diving-bell, in which the 

 compressed air was twelve times more dense than that on the tops of 

 mountains, — and when the lungs, with all the other bodily organs, can 

 so readily accommodate themselves to the most variable and trying cir- 

 cumstances, we do perceive how it is possible for respiration to be 

 carried on, notwithstanding these changes in a comet's atmosphere, 

 which, though undoubtedly extensive, yet take place in a slow, and 

 therefore harmless, manner. Another objection has been started to the 

 existence of living beings on comets, on account of the alternations of 

 light and darkness to which, in the opposite portions of their orbit, they 

 are thought to be exposed. But 1 find it remarked by Bailly, that the 

 Comet of 1680, supposing it at the aphelion to be 138 times more dis- 

 tant from the sun than the Earth, ought for this reason to receive five 

 times as much light from the sun as we do from the full moon ; and 

 when we add to this the superior density of the comet's atmosphere at 

 this distant part of its orbit, it is capable of obtaining a still greater 

 quantity of light by refraction *. 



" These explanations, then, if they be deemed correct, make it ap- 

 pear that the several changes which are produced upon the constitution 

 of a comet, in consequence of its varying distances from the sun, are 

 not incompatible with our ideas of animated existence, and go so far as 

 to render it not improbable, that the beings which inhabit comets may 

 even possess bodily frames resembling those of terrestrial beings* But 

 why, it may be asked, are we so solicitous to establish this resemblance 

 between ourselves and the inhabitants of a comet, as if that were a 

 condition which alone could render their existence possible ? When 

 we survey the wide field of animal organization which lies within the 

 scope of our own experience, from Man, the proud lord of creation, to 

 those tribes of zoophytes which we place lowest in the scale, do we not 

 behold a continual succession of beings, as infinite in variety as in 

 extent ? If, then, upon the surface of our own little planet, we behold 

 so diversified a picture of animal life, why should we deem it as either 



• Bailly, Hist. d'Astron. iii. 257. 



