Mr. A. Le Sueur on the Great Melbourne Telescope. 377 



Subjoined is a Table giving the dates of the various observations, 

 with the reference numbers corresponding to those on the diagram, 

 and with remarks on the state of the sky. 



Number 



in 

 diagram. 



Date of 

 observation. 



Eemarks. 



I. 



II. 



III. 



IV. 



V. 



VI. 



VII. 



VIII. 



IX. 



X. 



XI. 



XII. 



XIII. 



XIV. 



XV. 



XVI. 



XVII. 



XVIII. 



XIX. 



XX. 



XXI. 



XXII. 



XXIII. 



April 4th 



No mention of cloud. 



No mention of cloud. 



Extremely clear sky. 



No mention of cloud. [night by a halo. 



Sky not good ; thin hazy clouds, followed later in the 



Much wind. 



No mention of clouds. 



Occasional small clouds, and rather hazy. 



Clouds producing prismatic colours round the moon. 



Sky not good ; fleecy clouds. [clouds. 

 Bad night ; stopped after 10 minutes, in consequence of 

 Sky very clear. 



Occasional clouds. 



Sky hazy at sunset ; occasional clouds. [night. 



Sky apparently not quite so clear as on the preceding 



Fog and white frost, afterwards drift. 

 No remark about cloud. 



January 8th ...... 



April 8th 



January 9th 



March 8th 



April 9th 



January 10th ... 



February 9th 



January nth 



February 10th ... 



January 12th 



November 1 9th . . . 



March 13th 



April 13th 



April 1 4th 



April 15th .. 



January 1 6th 



September 20th . . . 

 February 1 6th ... 

 April 1 6th 



April 1 7th 



November 22nd. . . 

 November 23rd... 



" Observations with the Great Melbourne Telescope, in a Letter 

 to Professor Stokes." By A. Le Sueur. 



Observatory, Feb. 27. 



Dear Sir, — I have little more definite to tell you with reference 

 to the star y Argus. Thinking that a larger dispersion would be of 

 advantage, I have had a supplementary arrangement added to the 

 spectroscope, by means of which a direct prism may be interposed 

 between the collimator and the usual prism. 



With this increased dispersion, the red line keeps its place ; the 

 yellow one turns out to be slightly more refrangible than D. 



The green lines, which, with the smaller dispersion, were very 

 difficult, now become almost unmanageable ; this would seem to 

 throw some doubt on their reality, as mere extra dispersion should 

 have little effect on real lines. 



The direct prism being a small one, does not take in the whole of 

 the pencil when condensed to the limits bearable by the collimator ; 

 but as the arrangements at my disposal do not in any case admit 

 of utilizing the full condensation, the smallness of the prism has not 

 had any material effect. 



On the whole, I am now inclined to think that, with respect to 

 Phil. Mag. S. 4. Vol. 40. No. 268. Nov. 1870. 2 C 



