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Monday, X^tli April 1853. 

 JOHN CAY, Esq., Advocate, in the Chair. 



The following Communications were read : — 



1. Notice of recent Measures of the Ring of Saturn. By 

 Professor C. Piazzi Smyth. 



This communication chiefly described the observations made by 

 W. S. Jacob, Esq., of the Madras Observatory, during the last appa- 

 rition of the planet, with a telescope having a six-inch object-glass, 

 lately completed by Lerebours and Secretan. 



Previous to its being sent to India, the object-glass had been tested 

 at the Edinburgh Observatory ; and its quality, which was then ap- 

 proved, had been more conspicuously brought out in the subsequent 

 trial in a clearer climate. 



Immediately after the receipt of the object-glass, in September 

 1852, Mr Jacob directed it to Saturn, then in the zenith, and im- 

 mediately perceived the " transparency" of the dark ring which has 

 since been discovered independently by Mr Lassel and others ; and 

 on very accurately adjusting the focus, he saw a fine division in the 

 outer dark ring. This appears to have escaped all other observers 

 at the same time, except perhaps Mr Dawes, who had some suspi- 

 cions of such a phenomenon. But Mr Jacob saw it clearly for all the 

 rest of the apparition of the planet, could trace it through more than 

 half the circumference of the ring, and was enabled to get good 

 measures of it with the wii'e micrometer. 



Such a fine division of the outer ring has not unfrequently been 

 suspected before, and even seen, but only on one or two special nights, 

 by each observer, and then merely through a very small part of the 

 circumference at the ansse, 



Mr Jacob's observations, therefore, establish the fact permanently 

 among the phenomena of the planet's appearance, and lead us to ex- 

 pect more still from him, when, as will be the case in a few years, 

 the ring of Saturn is presented to our view at its maximum angle 

 of inclination. 



The author then concluded with an account of the most probable 

 theory with regard to the material and economy of the rings, 

 which he conceived to be fluid and vaporous, and indicating, with 



