An account of the discoveries concerning comets, with the way to find their orbits, and some improvements in constructing and calculating their places. For which reason are here added new tables, fitted to those purposes; particularly with regard to that comet which is soon expected to return / [Thomas Barker].

  • Barker, Thomas, 1722-1809.
Date:
1757
Catalogue details

Licence: Public Domain Mark

Credit: An account of the discoveries concerning comets, with the way to find their orbits, and some improvements in constructing and calculating their places. For which reason are here added new tables, fitted to those purposes; particularly with regard to that comet which is soon expected to return / [Thomas Barker]. Source: Wellcome Collection.

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    he expected that time and pains would difcover what was then unknown, and: feveral places there is a better guefs about comets, than any made for above fifteen hundred years afterward: and further fearch has fince con- firmed what he thought, that it is the excentricity of their orbits which; occafions their being only now and then feen, In all thofe dark ages, from the decline of the Roman empire to-the-Reformation, comets being only confidered as ominous meteors, three only have been yet found de- fcribed enough to determine their orbits, and thofe but in a grofs manner: and I think Appian was the firft, who, about 1530, began to obferve-their our air, they, having no fenfible parallax, muft needs be much further off than the moon: here then is the firft ftep toward finding out the true: nature of comets; and from that time all aftronomers have allowed their place to be-among,the planetary orbits, and many obfervations were made of their motions by, Tycho Brahe and others. ie eee The two comets of 1664 and 65, coming within a few months of one another, made many. perfons very inquifitive about them; and in Birch’s hiftory of the Royal Society, Vol. II. there are two remarkable gueffes, both read May. 23, 1666.> In page 93, are Mér. Hooke’s remarks.on Monj. Petit’s differtation on the nature of comets, prefented. to. the fociety fome weeks before. What that paper contained does. not fully appear; but Mr. Hooke faid, the hypothefes were very. ingenious, and fome of them not improbable, but whether the comets were moved in. equal fpaces of a curve line in equal [paces of time,. which Monf. Petit feemed inclined to believe, deferved to be further examined. This laft claufe is remarkable, and that paper, if ftill preferved, is worth fearching, to fee how near Monf, Petit was to gueffing the truth. . The other paper, page g1, is Mr. Hooke’s own, endeavouring: to account for the planet’s motions; where, having propofed the refiftance of the ether, he fays, the fecond caufe of infletting a direét motion into a curve may be from an attractive property of the body placed in the center, whereby it. continually endeavours to, attrac. or. drawsit to itfelf: for if fuch a principle be fuppofed, all the phenamena of the planets feem poffible.ta be explained, . by the conynon principle of mechanick motions; and poffibly the profecuting this Speculation may give us a true hypothefis of their motions.——By this hypothe/is the phenomena of the comets as well as of the planets may be folved, and the motion of the fecondary as well as of the primary planets: the motion alfo of the progreffion of the auges is very evident. This I think was much about the time that Sir Ifaac Newton difcovered the property ef gravity, and feems much like it; only Sir Ifaac, being the deeper mathematician, pro- fecuted the matter further, and cleared it up more fully. , Hevelius was too good an aftronomer, not to fee that comets were. far «a goat ae iit | | a largely 1 at ARs ERR RSE GE LENE LNs ict ete anes gobi}