178 Reviews — Oi'imheVs Geology of Bavaria. 



la IB AT" IIB ^VsT" s. 



I. — Geologie von Bayekn. Von Dr. K. Wilhelm von GtJmbel. 

 Erster Tbeil : Grundzuge der Geologie. I. Lieferung. Mit 

 zahlreiclien Abbildungen im Text. (Kassel, 1884.) 



ALTHOUGH this work is entitled " Geology of Bavaria," yet 

 the first part, containing the principles of geology, is altogether 

 of a general character, and apparently has no special relation to 

 i3avaria or other part of Germany. 



The first part of the work treats of the Hylology of the Earth, 

 that is, of the form and derivation of the materials of which the 

 Earth consists. This is divided into five sections, which respectively 

 refer to mineralogical, petrographical, morphological, petrogeneric, 

 and paleeontological subjects. 



The first number of 208 pages large octavo, with 145 woodcuts, 

 contains merely the first two sections relating to mineralogy and 

 petrography. The author's classification of the different rocks has 

 at least the merit of novelty, and we therefore venture to give an 

 indication of its character. The first leading group named Kokkite 

 is defined as an aggregate of chiefly crystalline particles, not in a 

 slaty form. This is subdivided into Homokokkite, when the 

 ci-ystalline rock consists of only one kind of mineral, such as ice, 

 rocksalt, g3'psum; and Heterokokkite, when it is composed of different 

 minerals with a crystalline, porphyritic, or amorphous ground-mass, 

 such as granite, trachyte, etc. The second main group named Hyalite 

 is defined as massive rock consisting of an amorphous glassy magma, 

 without regular inclosures, such as obsidian and perlite. The third 

 group is Phyllolithe, or thin-bedded rocks mostly of macrocrystalline 

 constituents, such as quartzitic and mica schists, gneiss, etc. The 

 fourth group, Pelolithe, consists of stratified, more or less massive, 

 apparently homogeneous rock, containing an intimate mixture of small 

 crystalline, clastic, and organically-formed particles. Rocks of such 

 different characters as quartzite, limestone, and marl are examples of 

 this group. The fifth group, Psepholite, embraces stratified rocks 

 consisting chiefly of readily recognizable fragments of older broken 

 up rock-masses, either loose or fii-mly united by some cementing 

 material. Under this are included, amongst others, sand, sandstone, 

 conglomerate, boulder-clay, volcanic tuff, etc. The sixth and last 

 main group, named Organolithe, is defined as stratified rock consisting 

 chiefly of remains of extinct organisms. This embraces chalk, deep- 

 sea mud, diatomaceous earth, and coal. 



We are afraid that in practice this classification will prove some- 

 what puzzling, since many stratified rocks will come under two or 

 even three of the leading groups. 



The descriptions of the different kinds of rocks appear to be very 

 satisfactory and reliable, and particular attention is given to their 

 microscopic structure, which is illustrated by numerous well-executed 

 w^oodcuts. These give this work a distinctive feature, and render it 

 highly valuable to the student. 



