468 ProceeiUugs of Philosophical Societies, [Dec. 



scope, power 160, in reference to the occultatidn of Saturn on 

 Oct. I^Oth. To each of them that part of the ring of Satwii 

 which last emerged from the moon's dark limb (neither of them 

 could observe the immersion) was rendered sensibly more 

 obtuse, and at the instant after separation approximating to a 

 rectilinear boundary. At the emergence of the eastern limb 

 of the glot)e of Saturn, a similar effect was observed by Mr. 

 Comfierd, but not by Mr. Wallis. 



A paper was next read, on the determination of latitudes 

 by observations of azimuths and altitudes alone, by M. Lit- 

 trow, Assoc. Ast. Soc. This paper includes the consideration 

 of four casfes. In the 1st, the latitude is computed from the 

 observed azimuth and altitude. In the 2d, two observed alti- 

 tudes are taken, and the two instrumental azimuths at the 

 same respective moments ; and the latitude is found from the 

 corrected altitudes, and the difference of the azimuths, with 

 the addition of an approximate latitude. In the 3d case, three 

 observed latitudes, and three corresponding azimuths, or two 

 azimuthal differences, are required ; and the latitude is thence 

 determined. In a 4th case, the problem is solved by means 

 of a watch instead of an azimuth circle ; there are supposed 

 given, the time of culmination only within half or three quar- 

 ters of an hour, three altitudes taken within that distance of 

 the meridian, and their intervals in time ; to find the true lati- 

 tude. The solutions to all the four cases are exceedingly 

 simple, and the resulting formulae admit of the utmost facility 

 of application. 



Lastly, there was exhibited to the Society, a model of one of 

 the large Reflecting Telescopes, made by Mr. John Ramage, 

 of Aberdeen, and of the stands, frame, and mechanism, for 

 facilitating its motions and adjustments. The reading of a 

 descriptive paper by Mr. Ramage, was also commenced ; but 

 its termination was postponed until the December meeting. 



MEDICO-BOTANICAL SOCIETY. 



Oct. 14. — ^This being the first meeting of the Society after the 

 recess, the Director (Mr. Frost) delivered an introductory dis- 

 course, describing the objects of the Society, &c. 



A Report of the various medicinal plants now in flower in the 

 gardens and stoves round the metropolis, was read. 



Some fine specimens of several species of Nicotiana, presented 

 by Mr. Anderson, were exhibited. 



'Nov. 11. — At this meeting, M. C. Friend, Esq. FRS. who had 

 just returned to England from Sierra Leone and Demerara, 

 announced to the Society that he had collected during his 

 voyage many kinds of bark, seeds, &c. used by the natives of 

 Cape Coast and Accra, as medicines, which he announced his 

 intention of presenting at the next meeting. 



