6 



Herman Schultz, 



portional to the time and labour actually employed in observation, or in 

 other words, that the observation of nebula 1 , with the parallel-line-microme- 

 ter is too tedious a work and, especially in so high a latitud, oltogether 

 inappropriate. On the other hand I can only express my opinion that the 

 parallel-line-micronieter is perhaps the only one of the instruments at pre- 

 sent employed, with which a really sharp determination of a nebula's posi- 

 tion is possible . and moreover remind the reader, that most observatories 

 are, as regards climatic circumstances, curiously enough, by no means ad- 

 vantageously situated, whereas in localities, which would in those respects 

 be best fitted for observation , there are either very few observatories or 

 none at all. It evidently follows from this, that an astronomer can not af- 

 ford to be very critical in the choice of the objects he observes, but is 

 rather obliged to try what can he done even when circumstances are not 

 particularly favourable. It is moreover a known fact in the history of sci- 

 ence that the best results have not always been exactly those, which have 

 been obtained under the most favourable circumstances; and indeed a coun- 

 tinghouse calculation of the proportion of labour bestowed to value received 

 is hardly applicable in science, where so many other factors usually enter 

 into the calculation. I should however in all probability long ago have 

 abandoned the observation of nebulae, had any such series at that time been 

 systematically carried on at any more favourably situated observatory; but, 

 as this, as far as I am aware, did not appear to be anywhere the case, I 

 considered myself bounden to continue in the path I had entered upon at 

 least untill the results obtained could be considered as forming a respec- 

 tably intire whole of a tolerably extensive compass, although reduced within 

 considerably narrower limits than those originally intended. 



When I first began to occupy myself with the observation of nebulae, 

 I was far from appretiating the difficulties I should have to meet. I soon 

 satisfied myself, that, with the Steinheil 13-foot-refractor that I employed, 

 I ought, at least in a dark field, to be able to sec all the objects regis- 

 tered in Sir John Hekschel's northern catalogue (Phil. Transact. 1833) 

 and even with tolerable certainty to determine the positions of the greatest 

 part of them with the parallel-wire-micrometer, if bright spider-lines on a dark 

 field were employed. Thus arose the plan of niicrometrically determining 

 the greater part ot the small centrally condensed nebulae occurring in that 

 catalogue, that lie north of the equator. I imagined that such a work, re- 

 solutely prosecuted, could not occupy very many years, even though it were 

 of course intended to observe every nebula several times, and micrometri- 

 eally to determine the most important faint neighbouring stars. But although 



