ANNIVERSARY ADDRESS OF THE PRESIDENT. Ixxxi 



The concluding observations of M. de Tchihatcheff will be found 

 of great interest in explaining the geological features of this 

 district, but I cannot allude to them any further. 



Dr. Hartung has published at Leipzig during the last year a 

 geological description of the Islands of Madeira and Poi-to Santo, 

 with a classified account of the fossil remains from these islands and 

 the Azores, by Dr. Karl Meyer. The names of these two authors 

 are so well known, that anything from them must be valuable. 

 Dr. Hartung, it will be remembered, accompanied Sir Charles Lyell 

 in his visit to Madeira in 1853 and 1854, and he continued his re- 

 searches in the islands after Sir Charles Lyell returned home ; and 

 when, after several years. Sir Charles was unable, in consequence 

 of other occupations, to carry out his intention of publishing a 

 full account of the geology of Madeira and Porto Santo from the 

 materials collected by himself and Dr. Hartung, he returned all 

 the documents to the latter for his own use. The present work is 

 chiefly founded on these materials. 



In describing the physical features of the island, Dr. Hartung 

 shows that its present outline is chiefly owing to the action of tlie 

 waves, that its valleys and ravines, and the long narrow crests 

 and mountain-ridges, are the result of erosion by running water, 

 and not owing to cracks and crevices produced at the time of the 

 upheaval of the island. Tracing back the first formation of the 

 igneous rocks, which form the basis of the island, to subma- 

 rine eruptions in early geological epochs. Dr. Hartung assumes 

 that the true volcanic formations are subsequent to the commence- 

 ment of the Tertiary period, the beds of which were deposited on 

 the surface of the already existing eruptive masses. The Tipper 

 Miocene beds of Madeira and Porto Santo, the marine organic re- 

 mains of which have been named and described by Dr. Karl Meyer, 

 afford the best proof of this. But on these marine beds, volcanic 

 rocks, 3000 feet in thickness, are superposed in the centre of the 

 island ; and this, together with other appearances in the island, 

 shows that the whole thickness of volcanic products which have 

 been deposited since the formation of the submarine Tertiary beds 

 cannot be less than 5000 feet. Dr. Hartung concludes his portion 

 of the work with some valuable remarks as to the periods when 

 volcanic activity ceased in Madeira itself and in the adjacent 

 islands, as well as with respect to the mode in which the nume- 

 rous hollows and ravines by which the former island is inter- 

 sected were hollowed out. 



In introducing his description of the marine fossils, Dr. Karl 

 Meyer, who is well known as a first-rate Tertiary conchologist, 

 makes the following remarks respecting the idea of spBcies : — " If 

 some of my determinations should appear incorrect to any palae- 

 ontologist, this is probably not so much owing to our holding 

 diflierent views respecting species, as to the greater or less com- 

 pleteness of material ; for, with regard to the idea of species, I feel 

 that I have adhered to the principle held by most conchologists, 

 according to which two allied individuals, though differing in some 



VOL. XXI. / 



