390 Proceedings of Philosophical Societies. [May, 



what he regards as the best means of carrying this method into 

 effect. 



A new annular Micrometer by Frauenhofer was submitted to 

 the inspection of the Meeting by Mr. Francis Baily. This 

 instrument is called by the artist the suspended circular 

 micrometer, from the circumstance of its appearing (in the 

 telescope) as if suspended in the heavens without any support. 

 It consists, in fact, of nothing more than a circular piece of 

 plate-glass about one-inch in diameter, in the centre of which a 

 circular hole is cut, of half an inch in diameter. To the inner 

 edge of this glass circle a narrow ring of steel is firmly and 

 securely fastened ; and, the whole being put in a lathe, the steel 

 ring is turned perfectly circular, and reduced to a very thin 

 edge, both at its exterior and its interior circumference. The 

 glass, with its steel circle, is then burnished into a brass ring or 

 cap, by means of which it may be placed, when required, in the 

 focus of the telescope. 



The advantages attending this construction are, 1. The preser- 

 vation of the circular form of the ring, as it comes from the 

 lathe, without the risk of its being injured in attaching it to the 

 telescope in the usual manner : 2. In the use of steel instead of 

 brass, whereby a finer edge may be given to the circumferences : 

 3. In rejecting the metal arms by which these rings were for- 

 merly attached to the sides of the telescope, from the unequal 

 expansion of which (or any external violence given thereto) the 

 perfect form of the circle might be injured, without being imme- 

 diately detected : 4. In thus avoiding the obstructions which 

 those arms might, in some cases, by their position, occasion in 

 the observations of the passage of a star before it entered the 

 interior of the ring. 



April 9. — At this meeting the following papers were read, viz. : 



1. On the Elements of the Orbit of the Comet of 1823, com- 

 puted from Observations made at the Royal Observatory at 

 Greenwich, by Mr. W. Richardson, Assistant to the Astronomer 

 Royal. These elements were computed by Dr. Olber's method. 

 The paper likewise contained a comparison of his elements with 

 the Greenwich observations from Jan. 1 to Feb. 2, and in more 

 than half the observations, the results of the elements did not 

 differ from them so much as 2' in longitude, or so much as 1- in 

 latitude. 



2. On the Corrections requisite for the Triangles which occur 

 in Geodesic Operations ; by Capt. G. Everest, of Bengal, Con- 

 ductor of the Trigonometrical Survey in India. This paper con- 

 tained the solution of two problems by formulae employed in 

 India since 1819, and which the author thinks preferable to 

 those given by M. Delambre for the same purpose. They 

 require the use merely of pocket logarithmic tables, with four 

 places of decimals, of which copious examples were given ; and 



