Astronomical Society. 137 



longitude is assumed equal to — 10 m 12 s . Diagrams, illustrating 

 the several phases of the eclipse, and apparently drawn up with con- 

 siderable care, accompanied these communications. 



Mr. Rumker of Paramatta, in New South Wales, communicated 

 the result of several series of observations in which he had been en- 

 gaged at the Observatory there. They contained, 1 st. The determina- 

 tion of the solstice in December 1826, June 1827, and December 

 1827. In deducing the results, he notices the insufficiency of De- 

 lambre's formula for the Reduction to the Meridian in cases of great 

 altitude : and suggests an alteration when the sun culminates near 

 the zenith. 2nd. Observations on the inferior conjunction of Venus in 

 December 1826. 3rd. Observations of moon-culminating stars during 

 parts of the years 1826 and 1827. 4th. Places of some of the fixed 

 stars in the southern hemisphere. 5th. A Catalogue of stars with 

 which the great comet of 1825 was compared. 6th. Corrected obser- 

 vations of the place of the said comet. 7th. A determination of the 

 latitude of the Observatory by reflection with the mural circle. 



The next communication was from Mr. Cumin of Bombay, giving 

 a more accurate account of his observations of moon-culminating 

 stars at that Observatory, during the year 1825 : from a mean of all 

 which, compared with corresponding observations at Bushey Heath, 

 and at Greenwich, he deduces the longitude of the Observatory equal 

 to 4 h 51 m 9 s east from Greenwich. 



Mr. Baily presented a short account of the two invariable pendu- 

 lums, the one of iron and the other of copper, which he had caused 

 to be made, agreeably to the order of the Council, and which are in- 

 trusted to the care of Captain Foster in his present voyage of experi- 

 ment and observation, for the purpose of investigating the possible 

 effects of the earth's magnetism in various geographical positions. 

 The form and construction of these pendulums are somewhat differ- 

 ent from those in general use ; consisting merely of a plain, straight, 

 uniform bar of metal : and, as he conceived that there is a consider- 

 able advantage in having each pendulum a convertible pendulum, he 

 has placed two knife-edges on each bar. This property of 

 convertibility, however, instead of being effected by a 

 sliding or moveable weight, is produced by filing away one 

 of the ends of the pendulum, until the number of vibra- 

 tions on the two knife-edges are equal. The mode of making 

 a pendulum of this kind he then describes in the following 

 manner : Take a plain straight bar of metal, two inches wide, 

 half an inch thick (or iths'of an inch if thought preferable) 

 and about 62i inches long $ at least it should not be shorter 

 than this, prior to the first trial for the adjustment. At five 

 inches from one end of the bar should be placed the apex 

 of one of the knife-edges, which he calls A, and at the di- 

 stance of 39'3 inches therefrom, should be placed the apex 

 of the other knife-edge, which he calls B ; each knife edge 

 being firmly and properly secured in the usual manner. 

 The distance of 39*3 inches is chosen, because the inter- 

 vals of the coincidences are in such case about 15 mi- 



New Series. Vol. 4. No. 20. Aug. 1 828. T nutes 3 



