Geology^ and Climate of the Island of Madeira. 365 



resemblance to coral, both in form and closeness of texture, it 

 may perhaps be considered a fair example of those substances 

 considered coral by Vancouver and Flinders. If this be ad- 

 mitted, it will follow that the reasoning is incorrect which is 

 founded on their supposed submarine origin." 



After returning home from Madeira, I had some sections of 

 the Oani9al structure made, thinking that they would form 

 good objects of microscopic inspection, as specimens of fossil 

 wood. In these sections there appeared, however, not the 

 slightest form or aspect of vegetable structure. The arrange- 

 ment of the calcareous matter was altogether similar to what 

 is found in corallines and marine animal productions. Their 

 vegetable structure was therefore rendered somewhat doubt- 

 ful. On heating a fragment in a glass tube, a great quantity 

 of ammonia was given off; which confirmed the idea of the 

 animal structure of the specimen, and shewed that the organic 

 matter had not, as was supposed, been wholly replaced by the 

 carbonate of lime and mineral deposits.* The formation is, 

 therefore, a tract of fossil coral, belonging probably, from the 

 appearance of the structure, to the family of Alcyonidse : tho 



* The folloAving is a detailed analysis which Mr Thomas Anderson of 

 Leith has had the kindness to make for me. 



"When heated to redness in a tube open at both ends, the fossil gave out a 

 strong smell of burning animal matter, becoming after a little powerfully 

 ammoniacal. 



; Dissolved in diluted nitric acid, a brown powder remained, which, wlien 

 ignited, left silica, the organic matter being dissipated. "* 



To the solution, rendered nearly neutral by evaporation, an excess of 

 ammonia was added, which threw down phosphate of ammonia. 



Carbonate of ammonia precipitated cai'bonate of lime. 



Quantitative Analysis : — 



Carbonate of lime, . . 73.15 



Silica, . 

 Phosphate of lime, 

 Animal matter, 

 Sulphate of lime, . 



"98.11 



This analysis, along with the sections, I think satisfactorily establishes 

 the animal origin of the formation. 



