314 Report of the Committee on the Melbourne Telescope. [Apr. 3, 



gular levers at the back of the great speculum is also contrived so as to 

 prevent them from exerting any pressure which might distort it. This is 

 a matter of the highest im.portance, and the attention of the Committee 

 was specially directed to it. They examined it most carefully, putting the 

 telescope in various positions of M> and P. D. on each side of the meridian, 

 both by day and night, and could not find any sign of flexure or any dis- 

 tortion of the image in any of these changes. 



6. In order to test the optical power of the second speculum B (the 

 first one. A, had been tried and approved by a member of the Com- 

 mittee on October 12 last), the telescope was directed to the following 

 objects : — In the daytime Venus and ct Andromedse ; at night (which 

 fortunately was clear and steady) Castor, the Great Nebula of Orion, 4 

 Orionis, y Andromed^e, Uranus, 1 Messier, 37 Messier, 46 Messier, and 

 51 Messier, from which it will be seen that both the light-collecting and 

 denning powers of the instrument were fairly tried. The powers used were 

 220 (the lowest which can take in the entire pencil), 3.50, and 450, all 

 negatives. Of course one would not propose such an instrument for the 

 measurement of close double stars, work for which telescopes such as 

 those of Poulkova and Harvard are possibly better fitted ; but the Com- 

 mittee found that the light even of large stars M^as collected into small, 

 hard, and perfectly circular disks, free from rays ; and though some 

 diffused light* surrounded them, it was exactly concentric with the central 

 disks. The 5th and 6th stars of the Trapezium of Orion were not only 

 plainly seen, but were very bright ; 'C Orionis was well shown, and the 

 companion of y Andromedse was clearly divided with the powers of 350 

 and 450, and the different tints of the components were evident. Uranus 

 was well seen, but v/as surrounded by such a multitude of very minute 

 stars that, without access to the tables of his satellites, it was impossible 

 to know whether any of them were seenf . 37 M. was broken into a heap 

 of stars so large and brilliant that it quite lost the character of a cluster. 

 The planetary Nebula in 46 M. brought out most strikingly the light- 

 collecting power of this telescope ; for it (which in most telescopes appears 

 as a faint disk) was revealed as a ring, bright even on the dazzling ground 

 of the surrounding stars, which here were as brilliant as the components of 

 the Pleiades appear in ordinary instruments. With respect to the Nebulae, 

 it is needless to say more than that Lord Rosse considers its performance 

 in bringing out the details of the Orion Nebula, 1 M. (the Crab), and 

 51 M. (the Great Spiral), quite satisfactory. 



7. The Committee had no opportunity of testing the spectroscope on 



- The cause of this diffused light has since been discovered and removed. 



t On the 19th of February, however, the Committee had the advantage of the 

 presence of Mr. Lassell in the examination of Uranus among other objects with Specidum 

 A, and, guided by his familiarity with that object, they were enabled to make out stars, 

 the positions of which, with great probability, corresponded to the places of the two 

 most distant, and one of the nearest satellites. 



