761 



of June, 1847, and of which a full abstract is contained in the fourth 

 volume of the 'Proceedings,' p. 691. The long historical memoir, 

 and quotations from former authors, have now been omitted. 



" Attempt to apply instrumental measurement to the Zodiacal 

 Light." By Prof, C. Piazzi Smyth. 



After describing the manner in which the zodiacal light was first 

 strongly represented to him in South Africa in 1843, and which 

 seemed to imply that some of the received opinions with regard to 

 it were erroneous, the author describes an equatorial instrument 

 which he contrived for the purpose of measuring the right ascension 

 and declination of the apex of the light ; some instrumental method 

 of determining these data, and thence the principal phenomena of 

 the appearances, being evidently desirable on account of the immense 

 extent to which the judgement may be biassed by prejudice or casual 

 circumstances, when the mere senses are trusted to for determining 

 the extent, situation and character of so faint and vague a body. 



The most favourable astronomical, atmospheric and personal con- 

 ditions requisite to obtain undeniable observations of the zodiacal 

 light are pointed out ; and aided partly by strict attention to these, 

 and partly by the clear atmosphere of the high mountains on which 

 he was then residing, the author found the phenomenon to be of a 

 far more stable and determinate character than has generally been 

 represented ; and his observations, made by the above instrument in 

 the years 1844-45, of which a list is given, seem to be affected with 

 a probable error not greater than 2°. 



Since his return from the Cape, the author's geographical position 

 has wholly prevented him from continuing his observations : he there- 

 fore now publishes his experiences to induce others in more favour- 

 able situations to follow up the subject ; which by comparing his 

 results with those of other observers in the northern hemisphere, 

 he shows has man}'- of its principal features in a state of ambiguity, 

 that ought not in the present day to be allowed to exist any longer ; 

 and further, to enable others to take up the subject as nearly as pos- 

 sible as he left it off', the author adds to his paper a series of views 

 of the different appearances of the zodiacal light at various seasons 

 of the year, and explains the peculiar projections employed to give a 

 true as well as a pictorial representation of the sky. 



The ordinary Meetings of the Society were then adjourned to 

 Thursday, November 16. 



June 9, 1848. 



The General Meeting for the election of Fellows was held this day, 

 The MARQUIS OF NORTHAMPTON, President, in the Chair. 

 The President addressed the Society as follows : — 



