146 Geological Society. 



Point, bearing south 79° W. by compass, distant from six to nine miles. 

 A considerable time afterwards the island divided itself into the form 

 of two pyramids, the most northern one crumbled away diagonally 

 towards the north, and the southern one disappeared in pieces, the 

 base however always remaining above the surface of the sea. At 

 half-past 7 o'clock the same island appeared again, or its size be- 

 came considerably increased, but shortly afterwards its summit be- 

 came flattened. At thirty-five minutes past 7 o'clock two other 

 islands appeared to the southward of the first. Of these, the most 

 southern bore south 56° west. The three islands ajDpeared to run 

 in the direction of north and south. The sea broke wdth violence 

 upon their shores and seemed violently agitated. In the distances 

 between these islands nothing was visible but chains of rocks, among 

 which a great explosion was discernible. 



" At eight minutes before 8 o'clock, the most northern island was 

 the only one visible : it appeared much higher than before, and of 

 the shape of a sugar loaf. The darkness of the night prevented us 

 seeing the other two islands. 



" The following day, the 13th of the month, at a quarter past 1 

 o'clock in the morning, the larboard watch and myself saw at inter- 

 vals a light in the same direction as the islands, south 72° west, 

 which appeared to be caused by a volcano. 



Position of the most northern island : 



Long. W. of meridian of Cadiz, 70° 33' (76° 52' W. of Greenwich.) 

 Lat. S 33 34. 



Position of the most southern island : 



Long. W. of meridian of Cadiz, 70° 34' (76° 53' W. of Greenwich.) 

 Lat 33 40. 



" I consider my longitude to be correct from having sighted Juan 

 Fernandez on the 11th, at 8 o'clock in the morning, and compared 

 its bearings with my latitude by observation. 



" Signed, &c. &.c. &c." 



Mr. Caldcleugh adds, the master of another vessel reported that 

 the islands bore 30 leagues due east of Juan Fernandez ; and that a 

 ship had been despatched from Valparaiso to discover whether they 

 remained above water or had crumbled away. 



The larger Curauma Point, referred to in the declaration, is a bluff 

 point, about 400 feet in height, and situated to the southward of 

 Valparaiso. 



A letter was next read, addressed to Charles Lyell, Esq., V.P.G.S., 

 by John Buddie, Esq., F.G.S., on depressions produced in the sur- 

 face of the ground by excavating beds of coal. 



Subsidence of the surface invariably follows the working of the 

 subjacent beds of coal where sufficient supports are not left, but the 

 extent of the subsidence is governed by the following circumstances : 



1st. The depth of the seam of coal below the surface. 



2nd. The thickness of the seam or seams removed. 



3rd. The nature of the strata betw^een the surface and the seams 

 of coal. 



4th. Whether the pillars of coal are wholly or partially worked. 



