ANJSriVERSARY ADDRESS OF THE PKESIDENT. XCIX 



bear in mind, namely, that notwithstanding the growing import- 

 ance of the publications of the Palaeontographical Society, the 

 number of subscribers has not increased of late years to the 

 extent which is desirable. With a larger number of subscribers, 

 a still more valuable volume might be annually published. 



Prof. Theobald, of Chur, has published an important work on 

 Swiss geology, entitled ' Greological Description of the North- 

 eastern Mountains of Grraubtlnden ' (Grrisons). The district is 

 one of the most mountainous in Switzerland, lying on both sides 

 of the Upper and Lower Engadin. The difficulty of any scientific 

 inquiry in these elevated regions, amidst glaciers and fields of snow, 

 is, as Prof. Theobald observes, increased by the peculiar nature of 

 the Alpine rocks and their disturbed stratification, where overturns, 

 displacements, and contortions are the most ordinary occurrences, 

 so that for great distances the superposition of the older to the 

 younger rocks becomes the rule. Moreover, the highly developed 

 metamorphism of the beds, in consequence of which the same rock 

 appears under the most varied and dissimilar forms, and the want 

 of well-preserved fossils throughout tbe greater part of the district, 

 greatly increase the difficulty. 



It is now generally known that the Alps do not consist so much 

 of one mountain-chain as of a series of central masses, round 

 which the younger or newer formations are grouped. These 

 central masses consist chiefly of gneiss and its associated crystal- 

 line schists, as bornblende and mica-schist. Hollows or deep 

 depressions filled with sedimentary rocks lie between these central 

 masses, and separate them from each other. But these central 

 masses are often broken up, and with the surrounding sedimentary 

 rocks form a series of undulations, instead of single centres of 

 elevation. 



These crystalline central masses have not only burst the over^ 

 lying capping of sedimentary rocks and pushed them on one side, 

 but even appear themselves as burst or broken domes of two dis- 

 tinct characters. Either the layers of the crystalline schists fall 

 away in an anticlinal direction on both sides of the central point 

 or central line, or they are still more lifted up, have separated in 

 a fan-shaped manner, and have been thrown over at their ex^ 

 tremities, so that they overlie the sedimentary rocks which have 

 been equally turned over. In both cases massive crystalline rocks 

 generally rise up in the middle, but not always ; and the non-crys- 

 talline roclvs surround them in long lines called undulations of 

 elevation ; they have undergone their greatest amount of eleva- 

 tion near the central masses, where they have also been most 

 destroyed, whereas they gradually become more horizontal towai'ds 

 the plain. The force which has raised these central masses has 

 not been sudden or spasmodic, but slow and gentle and con- 

 stantly operating. True eruptive rocks have sometimes bixrst 

 through the broken-up covering and completed what the meta^ 

 morphic elevation had commenced. This metamorphism, how-^ 

 ever, is not confined to the true crystalline rocks, but many of 



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