Art. I. — Observations on Donati's Comet, made between Oct. 

 12th and Nov. 12th, 1858. By Ludwig Becker, Esq. 



(With five Plates.) 

 [Eead before the Institute, March 30th, 1859.] 



Donati's Comet was first seen at Melbourne a little before 

 seven o'clock on the evening of the 11th October, 1858. 

 Previously to that date the sky had been clouded for several 

 days, and as it was not known then, on our side of the globe, 

 that a Comet, visible to the naked eye, was near us, its ap- 

 pearance surprised every one who noted the beauty of the 

 evening of the 11th of October. The silvery twilight near the 

 horizon formed the base of a well-developed zodiacal-light, 

 the pink-colored upper part of which reached the deep indigo 

 of an almost tropical evening sky. The young moon stood, 

 like a key-stone, on the top of the pointed arch of the 

 zodiacal-light ; and close to her, in her greatest brightness, 

 Venus and the fiery Antares. Looking at that splendid 

 constellation, the observer perceived, nearly due west, a streak 

 of light like a small, lonely cloud. There it stood, motionless, 

 its luminosity slowly increasing — and before a minute of time 

 had passed on, the cry was heard : — a Comet, lo ! a Comet ! 



On the following day (12th Oct.) I made every preparation 

 at the Magnetical Observatory, on the Flagstaff Hill, to pro- 

 cure as good and as many drawings of the Comet as possi- 

 ble. In this Professor Neumayer, the director of the 

 magnetical survey, most kindly assisted me, by allowing me 

 the use of his largest telescope, from Munich (Steinheil's), 

 and supplying me with some necessary exact data. 



Place of observation : — Melbourne, Flagstaff Hill Obser- 

 vatory, lat. 37*48 S., long. 145 E.; elevation above sea, 120 feet. 



The refractor used had a magnifying power of 79 linear ; 

 diameter of object glass, 3*020 inches; diameter of ocular 

 glass, 0."6; focal length, 51*16 inches. 



Fig. I.*— (Oct. 12.) 



[Sky, perfectly clear; wind, S.E., very light; barometer (reduced to 32* 

 Fahr.), 29 - 95; thermometer, 54 - 9 ; electricity (according to Quetelet's 

 electrometer), + 7 "09 ; remarks, lightning towards E.] 



* Each Fig. shows generally two representations of the Comet, the one 

 as seen with the naked eye, the other as it appeared in the telescope ; but 

 having the reversed image in the refractor drawn, according to nature, in its 

 true position. — L. B. 



B 



