236 Appearance of H alley' s Comet. 



German sulphuric acid diluted with water becomes white when 

 the latter gas is passed through it, as it always contains sul- 

 phurous acid. 



5. The arsenic always exists in sulphuric acid in the form of ar- 

 senious acid, never as arsenic acid. 



6. Concentrated boiling sulphuric acid can dissolve one third of 

 its weight of arsenious acid, of which the greater part separates on 

 cooling. The arsenious acid may be precipitated in a great measure 

 from the concentrated sulphuric acid when cooled, by absolute al- 

 cohol, although it is somewhat soluble in alcohol. 



7. Lastly, it is absolutely necessary that in all preparations to be 

 used internally, rectified, or at least German sulphuric acid should 

 be employed. — Thomsons Records of Science, July 1835. 



APPEARANCE OF HALLEY's COMET. 



Communications have appeared in the daily journals from our 

 correspondent the Rev. Dr. Hussey, and from Sir James South, 

 from which we derive the following particulars of the discovery of 

 Halley's Comet, in its present approach to the Sun, by those astro- 

 nomers. 



The Rev. Dr. Hussey observed the Comet at the Rectory, Hayes, 

 Kent, on the mornings of Sunday and Monday, August 23 and 

 24, and gives for its approximate place JR 5 h 42 m 20% N. Decl. 

 23° 45' 20"; stating it to be very large, but the faintest object the 

 eye can distinguish, in an achromatic telescope of 6*5 inches aper- 

 ture; and comparing it, in another communication, to the finest 

 smoke. 



Sir James South also observed the Comet at his Observatory at 

 Kensington, in the form of a round, well-defined, but extremely 

 faint nebulous body, perhaps 2 minutes of space in diameter, on 

 Sunday morning, August 23, at 1 hour 11 minutes sidereal time; 

 in about JR 5 hours 42 minutes 31 seconds ; and N. Decl. 23° 43'. 

 On Monday morning, August 24th, at 23 h 55 m 47 s sidereal time, 

 its place was JR 5 h 43 m 18 s , N. Decl. 23° 49' 43". 



The place assigned to it in the Nautical Almanac, for August 23, 

 is JR 5" 42™ 56 s , N. Decl. 24° 45'*3; so that, as Mr. Lubbock has 

 remarked, the agreement with calculation of its observed place is 

 as near as could have been hoped for. 



It is stated in a foreign journal, that a letter had been received 

 from Prof. Encke, announcing that the Comet had been discovered 

 by M. Kunowski at Berlin on the 22nd of August. 



In addition to MM. Damoiseau, Pontecoulant, and Rosenberger, 

 who have each gone through laborious calculations requisite to 

 predict the return of this Comet, Dr. Lehrman has also investi- 

 gated this question and arrives at very different conclusions. Ac- 

 cording to this mathematician the Comet will pass through Ursa 

 Minor, and the time of the perihelion passage which he assigns is 

 ten days later than that previously determined. Dr. Lehrman has 

 given his results in two recent numbers of the Astronomische 

 Nachrichten. 



