ECLIPSE OF THE SUN.

Timaru Herald, Volume XLII, Issue 3412, 3 September 1885, Page 3

ECLIPSE OF THE SUN.

[Specially Written tor tiie " Timaru Herald." The following particulars m reference to tho eclipse of the sun which will occur next Wednesday, September 9th, may bo of interest to our readers : — An eclipse of the sun, unless total, is of comparative little scientific value, except as evidence of tho nicety of astronomical calculation of the periodic movements of the moon ; but when total, it affords an opportunity of examining thc wonderful corona of light nnd the flames which encircle the sun, which, m the ordinary glare of sun light, are invisible. During the fenminutes of total obscuration of the sun's light which occurs during total eclipses, these flames have been measured by micrometers attached to telescopes, ond analysed by the spectroscope so precisely that it is known that they extend as far as 70,000 miles from tho sun'sdisc, and that they arechiefly composed of incandescent hydrogen gas. It is to tho spectroscope that we owe tho discovery that the great mass of the sun is composed of such matoriols as iron, sodium, magnesium, copper, etc., m a state of combustion, and that it is surrounded by a vast fiery envelope of hydrogen gas. Although it is possible, even without an eclipse, to bring thc spectroscope to bear on these hydrogen flames, yet the advantage afforded by total eclipso of sunlight is such that astronomers are eager to avail themselves of every opportunity of the kind, and the more so, becauso o concurrence of favorable conditions, such as convenience of place, time, and considerable duration of totol obscurity is rare. New Zealand is favorably situated for this eclipse, but, os it happens that the duration of the totality of eclipse will be very sliort, it is not likely that astronomers will visit us from other countries. An eclipso is total only to those portions of the earth's surface which lie under the centre of the curie of the shadow cast by the moon ns she passes across the sun, when she is suiliciently far from tho earth to appear slightly larger than the sun. The circle of total eclipse cast by the moon upon the earth is about 50 miles m diameter j outside this circle tho eclipse is partial, and outside a certain circle of pirtial eclipse thero is ro eclipse at nll. On this occasion Masterton m the Provinco of Wellington is situated centrally for the total eclipse, and there astronomers will gather together to use their telescopes and spectroscopes on the corona and sunllamcs. Hero, at Timaru, we arc outsido the magic; circle of total darkness, but the phenomena will bo full of interest, oven to the ordinary star-gazer, ns roughly speaking, 6-7ths of tho sun will bo obscured, ond, if the morning be fine, the diminution of light will be very remarkable. The eclipse will begin hero at 7 hours 23 minutes 42 seconds o.m. on September 9th, and will end nt 9 hours 14 minutes 43 seconds am., by the timo shown bythe Tost-oH'ieo clock, or, let it be Baid, by the time which ought to be shown by the clock, which is supposed to keep New Zealand mean time, reckoned from tho meridian l72dcg 30min, as an overage for oil Now Zealand. Between this average time ond the octual timo at thc longitude of Timaru there is a difference of fivo minutes, 60 that the clock time here is five minutes ahead of the actual timo of the eclipse. This is allowed for, together with the fact that the sun, ot this t ime of y car,is about 2 J m mutes before the elc ck. Thc eclipse will not be seen m Australia, as it ends thero at sunrise. Tho line of central eclipse traverses the Antarctic and Pacific Oceans, nowhere crossing land convenient for observation except m tho vicinity of Masterton. The eclipso may bo well Been with tho oid of smoked glass, but should any observer use opera-glasses or a small telescope, care should bo taken to cover the oyo end of tho glass with some opaque glass, either smoked, or deeply colored, as otherwise serious injury moy occur lo the sight m on instant. Largo telescopes aro oiways provided with dark glasses.