166 Notices and Extracts from the Minutes of the Geological Society. 



These last two seem to be connected with the alluvial deposits of tin^ which 

 are here so abundant, and are worked to such advantage. The principal mines 

 on the peninsula, are at Salengore and Pera, where they appear to be similar 

 in position, and to be worked in the same manner with those of Banca. The 

 tin is found in horizontal beds alternating with clay strata, and is so pure as to 

 require only to be washed and fused. The position and origin of this tin is a 

 subject of curious inquiry. 



I have as yet been too short a time at Sumatra to say much of it, but it pro- 

 mises to afford a most interesting field of research. On it the primitive and 

 volcanic ranges appear to meet ; the former descending in a south-eastern 

 direction from the Himalayan range, through the Malay peninsula and the 

 parallel island of Sumatra, till it meets the volcanic series, which runs from 

 thence nearly east, through Java, and the chain of islands that lie off the east- 

 ern extremity of that island. 



5. Notice on a recent Deposit of Compact Limestone. By Charles Stokes, Esq. 

 F.R. and L.s. M.G.s. &c. [Read December 15, 1820.] 



The fact which I am about to describe, appears to me to throw some light 

 upon the formation of some of the compact beds of limestone, in which, as in 

 the mountain limestone, fossil shells and corals are so completely preserved as 

 to retain their most minute parts in a perfect state. 



A short time since a mass of fragments of recent corals and shells, which I 

 believe to be from the Mediterranean, was brought to me on account of a 

 number of terebratulaB being fixed upon it. As they adhered chiefly to one 

 surface of the mass, I broke it to reduce its size ; but was much surprised on 

 doing so to find irregularly mixed with the mass a considerable quantity of 

 limestone, which had all the appearance and the fracture of a mountain lime- 

 stone, or the more compact kinds of white lias. And on more minute exami- 

 nation, I was convinced that this limestone was a quite recent deposit among 

 the branches and fragments of the coral. 



The chief part of the mass consists of pieces of the red coral of the Medi- 

 terranean, CoralUum rubrum of Lamarck (Isis nohilis, Linn. ; Gorgonia pre- 

 tiosa, Solander and Ellis), many of which I found running completely through 

 the limestone, and retaining still their well known red colour. As this coral 

 could not penetrate any solid substance, much less a compact rock, — for it can 

 increase in size only by the uninterrupted growth of the small animals which 

 secrete the matter of it, — it necessarily follows that the liuiestonc must have 

 been deposited around the coral. 



