4.2 Whether a Comet mayjir'iie and dejirey the EartS. 



the furface of that ftar. We may alfo conjefture, that the fatellites have been formed in *• 

 like manner by the atmofpheres of the planets. The five phenomena abovementioned natu-^ 

 rally flow from thefe hypothefes, to which the rings of Saturn afford additional probability." 

 (Vol. ii. p. 301.) 



The five phenomenaenumerated by the author are : (i) The motions of the planets in the 

 fame dire£lion and nearly in the fame plane. {2) The motions of the fatellites in the fame 

 direftion as the rotations of their planets. (3) The rotations of thefe different bodies and^ 

 of the fun in the fame dire£tion as their projeftile motion, and in planes very little differ- 

 ing from each other ; andlaftly, (4) The eccentricity of the cometary orbit&, 



This great eccentricity of the comets, and their motions in all direftions, appear to the 

 author a.fufficient reafon to conclude, that their origin is different from that of the planets. 

 He afterwards enquires into the probability that a comet may flrike the globe of the earth, 

 and deftroy its prefent regularity of appearance, &c. 



Thefe are his words, (vol. ii. p, 60.) " The fears which the appearance of comets at 

 that time infpired, were fucceedcd by an apprehenfion of another nature ; left, among the 

 great number which traverfe the planetary fyftem in every dire£tion, one of them fliould 

 deftroy the earth. They pa/sfo rapidly near us, that the effeB of their attraBion is not to he 

 feared. It is only by actually ftriking the earth that they could produce the dreadful effe£l : 

 but the (hock, though poffible, is fo very improbable in the courfe of an age ; it would re- 

 quire foextraordlnary a chance for the concurrence of two bodies fo fmall with refpe£t tO' 

 the immenfity of the fpace in which they move, that no reafonable ground of fear can be 

 maintained in this behalf. Neverthelefs, the fmall probability of fuch an event, if it be con- 

 fidcred with rcfpeft to a long feries of ages, may become very great. It is eafy to imagine 

 the effects of fuch a fliock upon the earth. The axis and rotatory motion being changed, 

 the feas abandon their former pofition, and rufli to the new equator ; great part of the 

 men and animals drowned in this univerfal deluge, or deftroyed by the violent ftrokc 

 jmprefled on the terreftrial globe ; entire fpecies annihilated ; all the monuments of human 

 induftry fwept away: — fuch are the. difafters which might enfue from the fhockof a comet. 

 We fee therefore why the ocean has formerly covered the high mountains, on which it has 

 left indubitable marks of its prefence •, how the plants-and animals of the fouth may have 

 exifted in the climates of the north, where their remains and impreftions appear ; and laftly,. 

 by an event 01 this kind, we may explain the novelty of the moral worlds the regular proceffes- 

 of which can fcarcely be traced beyond three thoufand years. The human fpecies reduced,, 

 to a very fmall number of individuals, and to the moft deplorable ftate, entirely occupied 

 for a long feries of time In the care of its own prefervation, muft have totally loft the re- 

 membrance of the fciences and the arts ; and when the progrefs of civilization gave efEcacy to 

 wants of lefs immediate preflure, it became neceflary to repeat again the various gradations 

 of invention, as if men had then for the firft time been placed on the earth. But however 

 adequate the caufe may be to thefe phenomena, for which It Is afligned by fomc phllo- 

 fophers, I repeat, that we may be perfectly at our. eafe, with regard to fo terrible an event, 

 during the (hort interval of life individusl." 



XIII. On 



