264 Clusters and Nebulce. 



is confident that it was not there when he made his first draw- 

 ing in 1824, and re-examined it 1826, March 13, in a perfectly 

 clear air, in company with Mr. Bamage, the celebrated maker 

 of large specula. Nov. 11 of that year, Struve saw it in full 

 moonshine: 1827, Nov. 16 and Dec. 16, Herschel found that 

 it could not " be overlooked but by wilful inattention : " the 

 following March he found that it had greatly diminished. It 

 may very probably be variable, as Smyth supposes. As far 

 back as 1664, only two years after the Royal Society had 

 received its charter and its name, Hooke communicated to it 

 that he had " found those stars in Orion's belt which M. de 

 Zulichem" (i.e., Huygens) "maketh but three, to be five." This 

 seems vague ; but as the original figure of Huygens shows only 

 one group of three, the trapezium is probably meant; and if so, 

 the oth must then have been far more brilliant than at the date 

 of any subsequent observation. At present, it forms a good 

 test for object-glasses of moderate size ; though less serviceable 

 than if it attained a greater elevation. Dawes saw it with a 

 5-feet achromatic ; but this gives little encouragement to ordi- 

 nary eyes. I have repeatedly seen it with 5| inches, lying a 

 little outwards from the line joining the two n p, or fainter 

 stars. The effect of 14| inches of light may be estimated from, 

 the fact that, though rated 13 mag., this little point has been 

 seen by the American observers after sunrise. A more difficult 

 object is a 6th, yet minuter star, discovered by Sir J. Herschel 

 with Sir J. South' s 1 If -inch object-glass, and considered by 

 him to have only about ^ the light of the 5th. It lies, accord- 

 ing to Dawes, but 2"- 79 from the brightest, or most south- 

 erly, of the four old ones,* and consequently requires a superior 

 instrument to be cleared from its rays. The remarkable fact 

 pointed out by Sir J. Herschel, that ' ( the apparent inequality 

 of two stars seen at once in the same field of view diminishes 

 as the light of the telescope is greater," and which, he justly 

 adds, " ought to be always borne in mind when the comparative 

 magnitude of stars is under discussion," is curiously illustrated 

 in the case of these minute points, which Lassell found both 

 equally bright and easily seen. He calls them even brilliant ! 

 Such was the light even of his old 2-feet speculum under the 

 Maltese sky. Probably No. 6 may be variable, for Struve 

 could never see it at Dorpat, and Secchi missed it on one occa- 

 sion, though the atmosphere was beautiful ; and yet Lassell 

 had at one time thought it even larger than' 5. Dumouchel 

 and his successor Do Vico added three more stars, but Sir J. 

 Herschel could not find them, and the Cauchoix achromatic at 

 Ronxi was known to have a bad habit of pointing out little 

 comites that Lad no existence. Porro, however, the Paris 

 * Bond's drawing, by some oversight, makes the/ star the largest of all. 



