562 Reviews — The Neues Jahrhuch. 



(pi. ii.). C. W. C. Giimbel : Preliminary Observations on Deep-sea 

 Mud. L. Wurtenberger : The Origin of the Schaffhausen Falls of 

 the Ehine (woodcut). E. Linker The Constitution and Origin of 

 the Bunter Sandstone Formation of the East border of the Thurin- 

 gian Basin. C. W. C Fuchs : The Geological, Microscopical, and 

 Chemical Examination of the old Sedimentary formations in the 

 French Pyrenees, with especial reference to the metamorphosis of 

 these and other old rocks (pi. vii.). The conclusions arrived at 

 (p. 878) are as follows : — 1. Between the old sedimentary beds and 

 the granite there is, in many places in the Pyrenees, a seam of 

 metamorphic schist, varying in thickness. 2. The change begins 

 on the border away from the granite in faint traces, and generally 

 becomes stronger as we approach the granite. 3. These stages of 

 the metamorphism are not regular. Highly altered beds have less 

 changed beds between them and the granite ; and there are alterna- 

 tions of beds in different degrees of metamorphism. . 4. This com- 

 mences with the separation of small nodules in the clay-schist, which 

 gradually increase in number and size, and at last become andalusite 

 and chiastolite. During the development of these minerals, the rest 

 of the rock changes bit by bit into a confused mass of mica and 

 quartz, with some felspai'. 5. Lastly, real mica-schist and gneiss 

 are produced. 6. There are numerous transitions from the gneiss to 

 granite ; and throughout this rock, which may be termed " granite- 

 gneiss," there is no actual division between the two in structure. 

 7. The andalusite and the nodules in the mica-schist and gneiss 

 gradually, through pseudomorphic changes, become mica, and the 

 rocks are thereby so much the richer in that mineral. 8. The cause 

 of the mineral alteration is immediately due to molecular displace- 

 ments, brought about by chemical interchange of the elementary 

 constituents. 9. The alkaline earths and the abundant iron de- 

 crease ; and the alkalies and silica increase. 10. The alumina set 

 free by the change of the clay-schist into mica-schist, and further 

 into gneiss, originates the nodules and the segregations of andalusite 

 or chiastolite. 11. The organic material present in the clay-schist 

 diminishes gradually during the processes of change, but can still be 

 recognized in all metamorphic rocks. CI. Schliiter : Notes of a 

 Geologico-palaeontological Journey in South' Sweden (chiefly referi'ing 

 to the Chalk Formation) . H. J. Burkart : The localities of Mexican 

 Meteorites. C. W. C. Fuchs: The Volcanic Phenomena of 1870. 

 Ferd. von Hochstetter : The Internal Structure of Volcanos, and 

 Miniature Yolcanos in Sulphur (three woodcuts). C. Naumann : 

 Mohr's Theory of the Polar Flattening of our Planet. Fr. Pfaff: 

 The Influence of Pressure in Chemical and Physical Processes. P. 

 Groth : The connexion between Crystalline Form and Chemical 

 Constitution. Fr. Klocke: The Growth of Crystals (pis. vi. and ix.). 

 With this sketch of their varied contents, we direct the attention 

 of our readers to these later numbers of the " Neues Jahrbuch," 

 particularly noticing their richness in exact observations made by 

 lithologist adn mineralogist working with the microscope. 



T. E. J. 



