The Midnight Sun. 95 



THE MIDNIGHT SUN. 



BY THOMAS W. BURR, E.R.A.S., F.C.S, 



The December number of the Intellectual Observer contains 

 a notice of a very interesting work, entitled A Spring and 

 Summer in Lapland, by an " Old Bushman," which the re- 

 viewer introduces by some remarks on the influence over the 

 imagination of those regions of the earth which lie sufficiently 

 near the North Pole to exhibit the remarkable summer phe- 

 nomenon of an unsetting sun ; and proceeds to quote Long- 

 fellow's spirited lines, describing the effect on the " Ancient 

 Mariner " who discovered the North Cape, in which lines — 



" And touthward through the haze, 

 He saw the sullen blaze 

 Of the red midnight sun," 



we shall presently see there is an astronomical blunder. The 

 book of the " Old Bushman," which is replete with the most 

 interesting information in Natural History, also contains 

 a vivid description of this singular appearance, and these 

 notices have produced a shower of communications to the 

 Intellectual Observer asking an explanation, " how the sun 

 can be seen at midnight V Such inquiries are principally, as 

 may be imagined, from the more juvenile readers, and in conse- 

 quence of their number, the conductors of this journal, with 

 their usual readiness to gratify laudable curiosity, and impart 

 useful information, have requested me to give, as briefly and 

 simply as possible, the reasons of the phenomenon and the ex- 

 planation of the effects produced, which, it is trusted, will at 

 once clear the path for the younger portion of my readers, and 

 may also not be unacceptable to some " children of a larger 

 growth," whose astronomy has become a little rusty. 



The effect in question, it is obvious, involves a consideration 

 of the causes both of the seasons and of the various lengths of 

 day and night, and these are due to two peculiarities of the 

 earth as a planet, viz., the obliquity of the equator and ecliptic, 

 and the parallelism of the earth's axis. 



Every one knows that the earth revolves round the sun in 

 the period we call a year, and that it rotates on its axis in tho 

 time we call a day, including periods of light and darkness, 

 which, except on two days in the year, are unequal in all parts 

 of the earth except at the equator — tho days being long and 

 tho nights short in summer, and the days short and nights long 

 in winter, at each particular place. The two periods when the 

 days and nights are equal all over the world, consisting of 

 twelve hours each, are called the equinoxes, and occur about 

 21st March and 21st September, and were the orbit of the 



