ANNIVERSARY ADDRESS OF THE PRESIDENT. CXlll 



tained, and that the Belemnoteuthis is generically distinct from the 

 Belemnite, the opinion formerly given by Mr. Chaning Pearce and 

 Mr. Cmmington. 



We should not forget the second part of the papers of the Friends 

 of Natural History in Vienna, collected and published by the inde- 

 fatigable Haidinger, who, notwithstanding the political events of the 

 last year, has been enabled to produce this volume, containing in 

 connection with geology the following papers : — Reuss on the Fossil 

 Polypiaria of the Vienna Tertiary Basin, accompanied by eleven 

 plates ; Czjzek on the Fossil Foraminifera of the Vienna Basin ; 

 Barrande on the Brachiopoda of the Silurian Rocks of Bohemia (the 

 continuation of his former), with nine plates ; Morlot on the Geology 

 of Istria, with a geological map ; and Reissacher on the Auriferous 

 District of the Salzburg Central Alps. 



The cause of the production of dolomite having of late been matter 

 of much attention, perhaps it may not be out of place, before we 

 conclude, to notice a few circumstances connected with this subject. 

 From the time, now many years since, when our veteran and distin- 

 guished colleague. Von Buch, first advanced his views on the pro- 

 duction of certain dolomites, there has been much difference of opinion 

 as to the mode in which this compound of the carbonates of lime and 

 magnesia could have been formed. Facts have been adduced to show 

 that the dolomitic beds, commonly known as the magnesian lime- 

 stones, ranging amid the new red sandstone series of parts of England, 

 and considered equivalent to part of the Permian system of Sir Rode- 

 rick Murchison, had been deposited from water, in the same manner 

 as many limestones, and that the same had been the case vdth many 

 dolomitic beds occurring in different parts of Great Britain and Ireland 

 amid the more common calcareous accumulations of the carboniferous 

 or mountain limestone. Other facts have been brought forward to 

 sustain the opinion that many dolomitic masses, often of considerable 

 volume, were not in the condition of the first formation of such 

 masses, but were limestones changed by circumstances which had 

 added the carbonate of magnesia, so that the resulting product was a 

 dolomite. Like many questions involving the union of particles of 

 matter constituting certain mineral bodies, we should carefully weigh 

 the evidence adduced, so as to be sure we do not attribute to a single 

 mode of production those things which may have resulted from two. 

 The study of the manner in which minerals occur has shown us that 

 some of the same kinds have been formed from the solution in water 

 of the elementary body or bodies of which they are composed, and 

 also amid masses which have evidently been in a state of igneous 

 fusion. Take, for example, common rock crystals or quartz, — little 

 doubt can exist that their component particles of silica have been 

 gathered together as crystals in fissures and other cavities from liquid 

 solutions, and we find as well-formed crystals of the same mineral in 

 some porphyries, the igneous origin of which can scarcely be called 

 in question, the particles in both cases having been under such con- 

 ditions that they could approximate, and, under the influences pro- 

 duchig crystallization, be arranged in a definite manner. The same 



VOL,. V. — PART I. h 



