THE SUN AND SOLAR PHENOMENA. 59 



that it is impossible for us to estimate the impression they would make upon the ignorant 

 mind, transpiring under circumstances favourable to their full effect. To behold the 

 sun, after shining in all its glory, apparently lose a part of his disk, become more indented, 

 and then entirely invisible, while perhaps not a cloud has appeared upon the sky to 

 account for his change of aspect ; to witness nature in the clear day suddenly invested 

 with an unaccountable gloom, the larger stars becoming distinct, and the brute creation 

 exhibiting symptoms of restlessness and alarm ; to feel a chilling cold supplanting the 

 fervent heat of noontide, these are peculiarities calculated to excite the consternation of 

 uncivilised tribes, as well as of nations unacquainted with their true natural explanation. 

 They have accordingly arrested the tide of battle, and perplexed monarchs with fear of 

 change. In the first year of the Peloponnesian war, on a summer afternoon, there was 

 an eclipse of the sun that was nearly total. Thucydides states, that the sun looked for 

 a time like the crescent of the moon, and some stars appeared, but the full orb shone 

 out afterwards in all its lustre. Pericles, according to Plutarch, was then on board 

 his galley, about to proceed on a warlike expedition ; and it required some address on 

 his part to quiet the apprehensions of his troops, who looked upon the darkness as an 

 unfavourable omen. Not many years afterwards, when the Athenians were in desperate 

 circumstances in the harbour of Syracuse, and had resolved on retiring, an eclipse of the 

 moon happening at the hour appointed for the retreat, excited their alarms, caused a 

 delay, and led to the destruction of both fleet and army. Columbus once rescued himself 

 from circumstances of great difficulty, when in want of provisions which the Jamaicans 

 refused to supply, by means of a lunar eclipse. Knowing that it was nigh at hand, he 

 announced it to them as a token of the anger of the Great Spirit on account of their 

 inhospitality, which had the desired effect when the beautiful orb 'began to be impaired. 

 Chronology has derived much valuable assistance from the connection which superstitious 

 fear has recorded between particular events and these phenomena, for eclipses may be 

 calculated thousands of years backwards with the same precision as forwards. Thus the 

 coincidence between a total eclipse of the sun, a rare occurrence in the same region, and 

 the battle between the Lydians and Persians, establishes the date of the latter ; and the 

 very day on which the great battle of Arbela was fought is likewise known from its 

 taking place eleven days after an eclipse. 



A solar eclipse is occasioned by the dark body of the moon interposing between the sun 

 and the earth, and deflecting a shadow upon the latter. The shadow cast by an object is 

 merely an interception of the light of some illuminating body, and has its shape and extent 



determined by the form and relative magnitudes of the 

 two. If the moon were as large as the sun, her shadow 

 would be cylindrical, like the first figure, and of an unli- 

 mited length. If she were of greater magnitude it would 

 resemble a truncated cone, the diameter and length in- 

 creasing to an indefinite extent, as in the second figure ; 

 but being immensely inferior to the sun, she projects a 

 shadow which converges to a point, like that in the third 

 figure. This shadow, at the distance of the earth from 

 the moon, can never be more than about a hundred and 

 seventy miles broad ; and consequently the sun can never be totally eclipsed at the 

 same instant over a greater extent of terrestrial space. But as the earth is continually 

 moving, the shadow is a passing traveller, and sweeps over it; no total obscuration 

 of the sun lasting longer at one spot than about eight minutes. Although the limits 

 within which an eclipse is total are very circumscribed, it will be more or less par- 

 tial over an area having a diameter of five thousand miles. In the diagram, lines 



