Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/581

 ASTRO Before Chrift. An eclipfe of the fun foretold May 28 S8S by Thales, by which a peace; was brought about between the Medes and Lydians. eclipfe of the moon, which 523 July 16 wasAnfollowed by the death of Cambyfes. eclipfe of the moon, which 502 Nov. 19 wasAnfollowed by the flaughter of the Sabines, and death of Valerius Publicola. An eclipfe of the fun. The 463 April 30 Perfian war, and the falling off of the Perfians from the Egyptians.1 eclipfe of the moon, which April 25 wasAnfollowed by a great famine at Rome ; and the beginning of the Peloponnefian war. A total eclipfe of the fun. A 43i Auguft 3 comet and plague at Athens. A total eclipfe of the moon. 4i3 Auguft 27 Nicias with his (hip deftroyed at Syracufe. eclipfe of the fun. The Per394 Augufl: 14 fiansAnbeat by Conon in a fea-engagement. total eclipfe of the moon. 168 June 21 TheA next day Perfeus, king of Macedonia, was conquered by Pauius Emilius. After Chrift, An eclipfe of the fun. This is 59 April 30 reckoned among the prodigies, on account of the murder of Agrippinus by Nero. April 12 A total eclipfe of the fun. A fign that the reign of the Gordiani would not continue long. A fixth perfecution of the Chriftians. eclipfe of the fun. The ftars 306 July 27 wereAn feen, and the emperor Conftan'tius died. dreadful eclipfe of the fun. 846 May 4 AndA Lewis the Pious died within fix months after it. An eclipfe of the fun. And JeJ009 rufalem taken by the Saracens. terrible eclipfe of the fun. 1133 Auguft 2 TheA ftars were feen. A fchifm in the church, occafioned by there being three Popes at once. We have not enumerated one half of Ricciolus’s lift of portentous eclipfes ; and for the fame reafon that he declines giving any more of them than what that lift contains, namely, that it is moft difagreeable to dwell any longer on fuch nonfenfe : the fuperftition of the ancients may be feen by the few here copied. Eclipfes of the fun are more frequent than of the moon, Vol. 1. No. 21. 3

N O M r. 481 becaufe the fun’s ecliptic limits are greater than the moon’s ; yet we have more vifible eclipfes of the moon than of the fun, becaufe eclipfes of the moon are feen from all parts of that hemifphere of the earth which is next her, and are equally great to each of thofe parts ; but the fun’s eclipfes are vifible only to that fmall portion of the hemifphere next him whereon the moon’s ihadow falls. The moon’s orbit being elliptical, and the earth in one of its focufes, (lie is once at her leaft diftance from the earth, and once at her greateft, in every lunation. When the moon changes at her leaft diftance from the earth, and fo near the node that her dark ftiadow falls upon the earth, (he appears big enough to cover the whole difle of the fun from that part on which her (hadow falls ; and the fun appears totally eclipfed there’ for fome minutes : but when the moon changes at her greateft diftance from the eaith, and fo near the node that her dark (hadow is directed towards the earth, her diameter fubtends a lefs angle than the fun’s ; and therefore (lie cannot hide his whole di(k from any part of the earth, nor does her (hadow reach it at that time ; and to the place over which the point of her (hadow hangs, the eclipfe is annular, the fun’s edge appearing like a luminous ring all around the body of the moon. When the change happens within j 7 degrees of the node, and the moon at her mean diftance from the earth, the point of her (hadow juft touches the earth, and (he eclipfeth the fun totally to that fmall fpot whereon her (hadow falls ; but the darknefs is not of a moment’s continuance. The moon’s apparent diameter, when largeft, exceeds the fun’s, when leaft, only 1 minute 38 feconds of a degree ; and in the greateft eclipfe of the fun that can happen at any time and place, the total darknefs continrues no longer than whilft the moon is going 1 minute 38 feconds from the fun in her orbit, which is about 3 minutes and 13 feconds of an hour. The moon’s dark (hadow covers only a fpot on the earth’s furface, about 180 Englifti miles broad, when the moon’s diameter appears largeft, and the fun’s leaft ; and the total darknefs can extend no farther than the dark (hadow covers. Yet the moon’s partial (hadow or penumbra may then cover a circular fpace 4900 miles in diameter, within all which the fun is more or lefs eclipfed, as the places are lefs or more diftant from the centre of the penumbra. When the moon changes exactly in the node, the penumbra is circular on the earth at the middle of the general eclipfe ; becaufe at that time it falls perpendicularly on the earth’s furface ; but at every other moment it falls obliquely, and will therefore be ,elliptical ; and the more fo, as the time is longer before or after the middle of the general eclipfe ; and then, much greater portions of the earth’s furface are involved in the penumbra. When the penumbra firft touches the earth, the general eclipfe begins ; when it leaves the earth, the general eclipfe ends : from the beginning to the end the fun appears eclipfed in fome part of the earth or other. When the penumbra touches any place, the eclipfe begins at that place, and ends when the penumbra leaves it. When the moon chapges in the node, the penumbra 6F goes