264 THE POPULAR SCIENCE MONTHLY. 



was one of its most striking features. (Herschel's remarks in this 

 regard are fully confirmed by the best observers.) 



Biit, Bs we may see by a reference to Fig. 5, Herschel had discov- 

 ered quite a number of small stars, some of them extremely faint and 

 difficult, notably one marked 78 in the figure (No. 78 of Herschel's 

 Catalogue). 



Later researches on the stars in this group have added largely to 

 their number, but hardly any have been found more faint than this 

 star H. 78. 



Bond, of Cambridge, and O. Struve, of Pulkova, with the fifteen- 

 inch refractors of those observatories, both observed it and found it 

 extremely difficult, and both of these observers supposed it to be vari- 

 able in magnitude. It seems almost impossible that Herschel should 

 have seen H. 78 and that he should not have seen others seen by both 

 Bond and Struve, if the star was as faint in 1834 as it is in 1874 ; 

 and the inference seems hard to avoid, that this very faint star was 

 perceptibly brighter in 1834 than at present. 



Herschel discusses the evidences of change in the nebula at some 

 length, and, although his own drawings of 1824 and 1837 differ as 

 much as any two drawings which we have, he is strongly of belief that 

 these differences, although great, " are not more so than I am disposed 

 to attribute to inexperience in such delineations," and to various other 

 causes, such as the favorable situation of the nebula in the southern 

 sky, etc. One part of the nebula he does regard as probably variable, 

 and, to prove this, he compares his two drawings. It may be said 

 that, so far as our knowledge now goes, this suspicion of Herschel's is 

 not confirmed. 



In 1852, Mr. Lassell, already famous as the discoverer of various 

 satellites of the major planets, took his magnificent twenty-foot re- 

 flector to Valetta, to use it to good advantage in the serene atmos- 

 phere there. While his telescope was mounted at Valetta, Mr. Las- 

 sell made careful observations of the Orion nebula, and he even had 

 a painting in oil made from his own drawings, and from the nebula it- 

 self, by an artist-friend. When we consider the immense difficulty of 

 drawing even the form of so complex an object as this is at the tele- 

 scope, from which the eye must be removed every moment to add a 

 new line, or to verify one already drawn, and when we further consider 

 what added pains must be taken in order to get an approach to accu- 

 racy of light and shade, we must admit that the attempt to represent 

 not only form, and light and dark, but also color and tint, is almost a 

 vain one. Accordingly, we find Mr. Lassell's drawing of the nebula 

 itself to be strikingly different from Herschel's or Rosse's (made in 

 1867), but we ought not on that account assume any change in the 

 nebula itself. Any one who has made such drawings will know what 

 strong and direct evidence of change must be had to establish it as a 

 fact. 



