1825.] Geological Society. 149- 



threads suspended in the heavens. A short account of the cir- 

 cumstances vv'hich led M. Frauenhofer to this happy invention 

 was read. 



An engraving of Frauenhofer's achromatic telescope at Dorpat 

 of 14 feet focus and 9 inches aperture, was also submitted to the 

 inspection of the members by IMr. Herschel. 



A communication was read from Capt. Ross, dated Stranraer, 

 Aug. ~. 1824, in which he transmits a diagram exhibiting his 

 observation of the occultntion ofHerschel's planet by the moon, 

 on the preceding day, with Pkamage's 25 feet telescope, and a 

 power of 500. The planet appeared to have entered about one- 

 third of its diameter on the dark part of the moon before it dis- 

 appeared, and its light began to diminish before it touched the 

 lunar disc. On the contrary at its emersion, it appeared one- 

 fourth of its own diameter distant from the moon's western limb. 

 The whole time of the occultation was 1'' T" 44*5\ 



After this the reading was commenced of a paper by Mr. H. 

 Atkinson, of Newcastle-upon-Tyne, " On Astronomical and 

 other Refractions ; with a connected Inquiry into the Law of 

 Temperature in different Latitudes and Altitudes." As the 

 reading of this paper will be resumed at a subsequent meeting, 

 an abstract of the whole may with propriety be deferred. 



GEOLOGICAL SOCIETY. 



Dec. 3. — A notice was read, " On some Fossils found in the 

 Island of Madeira ;" by the late T. E. Bowdich, Esq. 



In this notice, the author describes a formation of branched 

 cylindrical tubes encased with agglutinated sand, which occur 

 in great abundance near Fanical, 15 miles from Funchal, in the 

 Island of Madeira. Mr. Bowdich is inclined to refer these to a 

 vegetable origin. They are accompanied by shells, some deci- 

 dedly terrestrial, and others which appear to belong to a marine 

 genus. In conclusion, some account is given of the general 

 tieatures and structure of the neighbouring district. 



An extract of a paper was then read, entitled, " An Inquiry 

 into the Chemical Composition of those Minerals which belong 

 to the genus Tourmaline ;" by Dr. C. G. Gmelin, Professor of 

 Chemistry in the University of Tubingen, and For. Mem. GS. 



Prof. Gmelin, in this memoir, details at length, the various 

 analyses of minerals of the Tourmaline family, which have been 

 made by former chemists. He then describes the methods 

 which he adopted in his own experiments, and adds the results 

 which he obtained from them. 



The author divides the different species of Tourmaline into the 

 following sections: 1. Tourmalines which contain lithion ; 

 2. Tourmalines which contain potash or soda, or both these alka- 

 lieB together, without lithion, and without a considerable quantity 

 of magnesia; 3. Tourmalines which contain a considerable 



