220 Astronomical Society. 



out freely, and chalybeate and saline springs occur at short distances 

 from each other. 



The coal of the colony appears to be a lignite, and is associated 

 with grey marlstone containing impressions of leaves of dicotyledonous 

 plants. The secondary rocks contain casts of Terebratulae and other 

 shells j but the author does not attempt to make out precisely the 

 order of superposition, or the equivalents of the strata. 



A memoir was then read " On the Geology of the Island of Juan 

 Fernandez, in the Pacific Ocean, by Alex. Caldcleugh, Esq. F.G.S." 



After a sketch of the past history and present state of this island, 

 celebrated as the place of exile of Alexander Selkirk and the scene of 

 the fabulous adventures of Robinson Crusoe*, the author proceeds to 

 state that it is about twelve miles in length and four in breadth, pos- 

 sessing three ports, and consisting of very high land, the culminating 

 point of which rises to about 3005 feet above the sea. 



The author could discover no trace of a volcano said to exist here 

 by former visitors j all the rocks, according to him, consist of basaltic 

 greenstone and trap of various mineralogical structure, both amorphous 

 and vesicular, together withtrappean concretions, no other contained 

 minerals being observable except olivine and metastique [?] . It is fur- 

 ther mentioned that the basalt in parts is almost columnar, and in 

 others has a peaked and serrated outline, the mass being, here and 

 there, traversed by dykes. 



Owing to the peculiar character of this basalt, and especially from 

 the great quantity of olivine, the author compares its age with that of 

 Bohemia, the Rhine, the Vivarrais, and Beaulieu in Provence. 



ASTRONOMICAL SOCIETY. 



Dec. 10, 1830. The following communications were read : 



I. On a Method of determining the Declinations of Stars with 

 one Mural Circle, by J. Pond, Esq. A.R. 



II. A Letter from Capt. Philip P. King, R.N.on a Comet seen near 

 the South Pole. " This comet was discovered by Lieut. Wickham, of 

 H.M.S. Adventure, on the night of the 1 8th of last March. An ima- 

 ginary line from y Crucis through a Crucis to the smaller nebula, 

 being crossed by another from Sirius through the larger nebula, 

 their intersection would be very close to the comet's position. It 

 was very bright and large. At midnight the following angular dis- 

 tances were measured with a sextant. 



Comet and a Crucis 31 50' 30" 



Sirius 71 0" 



Three weeks after, when Captain King had arrived at the Strait 

 of Magalhanes, the comet was too faint to be observed: it was seen 

 near 0, j/, <5 Junonis Pavo. 



* There appears to be some confusion in this statement, aiising proba- 

 bably from the prevailing, though, we believe, erroneous supposition, that 

 the fiction of Robinson Crusoe was founded on the real adventures of Alex- 

 ander Selkirk in Juan Fernandez. The scene of the adventures of Robin- 

 son Crusoe, as is evident from the particulars related in the narrative, is an 

 island supposed to be situated on the north-eastern coast of South America, 

 opposite the mouth of the river Amazons. EDIT. 



A notice 



