4 



Herman Schultz, 



ness to admit of being conveniently observed in the meridian and thus to 

 give tlie right ascensions and declinations of the observed nebulae. I have 

 more over in many instances also compared the nebulae with fainter stars 

 in their immediate vicinity, or, where it was found more convenient to do 

 so, compared such neighbouring stars of greater interest with the star of 

 comparison employed in observing the nebula. The whole number of single 

 measures, on which the results here registered are founded, amounts to 

 about 12000. I have in all cases appended to the position as careful a de- 

 scription of the nebula as circumstances permitted me to give. I ought at 

 once to mention that this series of observations is in many cases deficient 

 in that completeness of detail, which is desirable, as well, not to men- 

 tion other points, with respect to the observation of the fainter neighbouring- 

 stars, of which but few have as yet been observed, as also with respect 

 to satisfactoriness in the number of positions of the nebulae as refferred to 

 the stars of comparison. As however my observations have already been 

 protracted through so long a period, I have, in order not unnecessarily to 

 isolate my work, considered it wisest no longer to defer the publication of 

 the materials here before us, especially as I anticipate from such a commu- 

 nication some advantage towards the final completion of the work. I con- 

 fine myself for the present to communicating the evening-means ot the dif- 

 ferential-coordinates observed, and accordingly defer the calculation of de- 

 finitive means untill I have fully completed my own observations and suc- 

 ceeded in obtaining reliable positions for all the stars of comparison em- 

 ployed, so as to be able at the same time to give definitively the right 

 ascensions and declinations of the observed objects. 



It may seem astonishing that I have not during so many years collec- 

 ted a richer harvest of observations. But those, who are experienced in the 

 observation of such objects, will not need to be reminded how much time 

 is required for the determination by the parallel-line-micrometer of nebulae's 

 positions , and that under a northern sky such a work must necessarily 

 proceed with distressing slowness. The heavens at Upsala so rarely for 

 any length of time free from clouds, the almost always disturbed atmos- 

 phere, the long twilight at the seasons of the year most favourable for ob- 

 servation, and the remarkably brilliant aurora borealis during a conside- 

 rable part of the last few years, are all local circumstances that have left 

 but very few nights here disposable for the observation of nebulae, and 

 even among these only an extremely small number on which the observa- 

 tions could be made under circumstances favourable for the purpose. Add 

 to this, that so many clear nights were, in consequence of bright moonlight 



