Dec. 9, 1886] 



NA TURE 



135 



ASTRONOMICAL PHENOMENA FOR THE 



WEEK 1 886 DECEMBER 12-1S 

 CPOR the reckoning of time the civil day, commencing at 

 ^^ Greenwich mean midnight, counting the hours on to 24, 

 is here employed.) 



At Greenwich on December 12 

 Sun rises, yh. 59m. ; souths, iih. 53m. 58-03. ; sets, ish. 49m. ; 

 decl. on meridian, 23° 6' S. : Sidereal Time at Sunset, 

 2lh. 14m. 

 Moon (one day past Full) rises, l6h. 34m.* ; souths, oh. 29m. ; 

 sets, 8h. 27m. ; decl. on meridian, 18° 57' N. 



* Indicates that the rising is that of the preceding evening. -• 



0:€tiltattons of Stars by the Moon (visible at Greenwich) 



Correspond ins 

 TA- D angles from ver- 



D.sap. Reap. ,^^ ^^ ^jg^^ ^^^ 



inverted image 



Mag. 



3 Cancri ... 



B...\.C. 2731 



54 Cancri . . . 



h. 



... 6 



... 17 



6 ... I 42 ... 2 46 ... :co 237 

 6J ... 6 54 near approach 207 — 

 6A ... 21 26 ... 22 9 ... 85 iSi 



Mercury stationary. 



Saturn in conjunction with and 2° 59' north 

 of the Moon. 

 Variable Stars 



U Cephei 



.l/sisnifie 





Meteor-Showers 

 Moonlight interferes with meteor observation during the early 

 part of the week, which is also less fruitful of meteors than are 

 the first few days of the month. Amongst the radiants which 

 have supplied meteors at this season are one in the constellation 

 of the Lyn.x, R.A. IoS^ Decl. 63" N., and one in Quadrans. 

 R.A. 221°, Decl. + 53° N. 



THE LAW OF STORMS IN THE EASTERN 

 SEAS^ 

 I. TN the Eastern seas the earliest signs of a typhoon are 

 clouds of the cirrus type — looking like fine hair, feathers 

 or small pale white tufts of wool — travelling from the east or 

 thereabout, their direction backing towards the north, a slight 

 rise in the barometer, clear and dry but hot weather, and light 

 winds. This fine weather lasts for days, and the existence of a 

 typhoon at a great distance contributes therefore to the safety of 

 ships at sea, — a fact that is not sufficiently appreciated hy 

 mariners. 



The cirrus clouds, wh'ch frequently assume fantastic shapes, 

 make their appearance within 1500 miles of the centre of a 

 typhoon, the barometer is generally rising beyond from 6jo to 

 1000 miles of the centre, and the mean of the twenty-four hours' 

 temperature rises in Hong Kong above 81'. 



A swell in the sea is noticed within from 300 to 500 miles of 

 the centre, but this depends greatly upon the situation of the 



' \jy Dr. \V. Doberck, Hong Kong Government Astronomer. Reprinted 

 from the Hong Kong Telegra{lt. 



nearest land. Ilalos round the sun and the moon, phosphor- 

 escence of the water, and also glorious sunsets appear to be 

 frequently noticed before typhoons. 



Within about 800 miles of the centre the sky is generally 

 half covered with cumulus clouds, above which cirro-cumulus 

 are usually seen. South and south-west of the centre, thunder- 

 storms andcumulo-slratus clouds are observed. On approaching 

 nearer to the centre the cloudiness increases, the temperature 

 falls in consequence, and the mercury begins to descend in the 

 barometer. Then the air becomes oppressive from the increasing 

 dampness, a slight haze is observed during the morning hours, 

 and the sky presents a threatening and vaporous appearance. 

 Within 300 miles of the centre the temperature falls quickly 

 owinr lo the cumulus, roll-cumulus, or nimbus clouds, with 

 which the sky is nearly completely overcast. And meantime 

 the wind has risen and blows generally with the force of a strong 

 breeze about 300 miles from the centre. But this depends also 

 upon the bearing of the centre, the wind being usually strongest 

 in the right hand seinicircle. Within 150 miles of the centre 

 the sky is densely overcast with nimbus clouds accompanied by 

 heavy rain, and within 60 miles it generally pours down in 

 torrents, while the wind blows so hard that no canvas can 

 withstand it ; but there is no thunder and lightning. The tem- 

 perature at sea is frequently about 76°, and on ^hore about 78'. 



Within from 2 to 15 miles of the centre the wind either 

 calms down or blow only moderate breezes, and the sky 

 clears, being now covered only by very light clouds. The sea 

 is as a rule mountainous, but in so ne reports it is stated that the 

 sea had calmed down to some extent when the wind fell. Quan- 

 tities of sea-birds, and near land also butterflies and other insects, 

 cover a ship situated in the bull's eye of a typhoon. It is pos-ible 

 that the central calm does not quite accurately coincide with the 

 centre of the typhoou. 



The angle between the direction of the wind and the direction 

 of the radius (the straight line between the observer an:l the 

 centre of the typhoon) is, on an average, between 10° and 25° 

 latitude, 43' in front of the centre and 53° behind the centre ; 

 between 33° and 35° latitude, 65° in front and 85' behind ; and 

 between 10' and 35' it is abou* 49° in front and 62" behind the 

 centre. The angle appears to be smaller near the shore for 

 off-shore winds, and far out at sea the diflerence between the 

 angle in front of and behind the centre appears to be small. 

 The following rule for finding, on board ship in the China seas, 

 the bearing of the centre of a typhoon is, therefore, approxi- 

 mately correct : Stand with yjur back to the wind, and you 

 will have the centre on your left side, but 3 points in front of 

 your left hand ; i.e. the centre /'cars about xi points from the 

 wind. If your ship is in a very low latitude the centre may lie 

 as much as 4 points in front of your left hand, i.e. bear 12 

 points from the wind, and if you are in a hi^h latitude it may 

 bear only 9 points from the wind. Once the wind has reached 

 the force of a strong breeze, the average angle between the wind 

 and the direction of the centre does not appear to change at all, 

 but the wind, which blows in great gusts in a typhoon, may oscil- 

 late to both sides of the true value. There does not appear to 

 be any foundation at all for the belief that the wind near the 

 centre blows in circles round the centre. To act according 

 to this rule might prove disastrous to a ship experiencing a 

 typhoon. 



Very low clouds in a typhoon move with the wind, but if the 

 clouds are high they are frequently seen to move in a different 

 manner, and the following rule may then occasionally be of 

 use : If right in front of the centre, stand with your hack 

 towards the direction whence the clouds are coming, and you 

 will have the centre from I to 2 points in front of your left hand ; 

 and if straight behind the centre you may have it a point or two 

 to the left of the direction in which you are looking. 



Once the bearing of the centre has been ascertained,' the 

 master of a vessel in a typhoon requires to know in which semi- 

 circle, looking in the direction towards which the typhoon is 

 moving, he is^situated : If in the right hanj semicircle, the wind 

 will veer, i.e. .shift with the sun ; and if in the left hand semi- 

 circle, it will back, i.e. shift in the opposite direction. But this 

 rule is strictly applicable on board of a vessel only when hove- 

 to, or at any rate proceeding at a slower rate than the typhoin. 

 For a vessel moving at a faster rate than and in the same direc- 

 tion as a typhoon, the rule may be reversed. In case of doubt 

 it may therefore become advisable to heave-to in order to be 

 quite sure of the semicircle in which you are situated. But we 

 have seen that the wind moves in spirals towards the centre, and 



