474 



NATURE 



{Oct. 4, 1877 



to be affixed. Prof. Zirkel now introduces these pro- 

 visional and useful terms to English readers. " Opacite" 

 includes all the black opaque amorphous grains, scales, 

 and streaks which have resulted from the decomposition 

 of different minerals, and which, no doubt, vary widely in 

 chemical constitution. They probably in most cases 

 consist laigely of metallic oxides. " Ferrite "embraces 

 those yellowish, brownish, or reddish specks, grains, 

 veinings, or pseudomorphous crystals which occur in so 

 many rocks where oxides of iron have decomposed. 

 " Viridile " is the term applied to greenish transparent or 

 translucent scales, fibres, or veins, frequently seen where 

 hornblende, augite, or olivine have been alfered. They 

 must vary much in composition, sometimes approaching 

 chlorite, sometimes delessite or serpentine. 



These scientific terms may be usefully transplanted 

 into English textbooks. The only one which, though 

 the great need of such a word cannot be denied, seems 

 open to considerable objection, is " macroscopic." It is 

 too like " microscopic," whether as written, printed, or 

 spoken. " Gymnoscopic" would be better. Rut there 

 occur throughout the Report many nouns and adjectives 

 which the reader will in vain look for in any dictionary, 

 and the meaning of some of which he will not readily 

 appreciate if he does not happen to be familiar with the 

 German petrographical terms for which they are intended. 

 Such are " fibration," " lamellation," " inclusion," " zon- 

 ally," "lineated," " fluidal," "interwedged," and many 

 more. Even ordinary words are used in a way which is 

 apt to puzzle the uninitiated. For example, " some occur- 

 rences are poor in augite," " poorly-shaped crystals,'' 

 " drop-like or crippled minerals." The English language 

 is not quite so meagre as to be unable to furnish expres- 

 sion in already familiar words and phrases to the ideas 

 sought to be conveyed by these novel and sometimes 

 rather uncouth term=. 



After a brief chapter devoted to the crystalline schists 

 and their related rocks, the author proceeds to what are 

 commonly known as the igneous rocks, beginning with 

 granite and the early intrusive porphyries and felsites, 

 passing thence through the diorite, diabase, gabbro, and 

 other groups, into the wide series of tertiary volcanic 

 products. V. Richthofen's name propylite is retained for 

 the oldest eruptive rock of the tertiary series— a mixture 

 of plagioclase felspar with hornblende, having most of the 

 characters of the old diorites and dioritic porphyries. 

 The petrographical differences between this rock and an- 

 desite are carefully summed up by Prof. Zirkel ; but 

 at the most they appear to be rather fine-drawn. He 

 insists that rocks of different geological date can 

 be distinguished petrographically, and that this may 

 be done even among the different members of the 

 tertiary series. Undoubtedly the most important chapter 

 of the Report is that devoted to the trachytic and rhyolitic 

 rocks. Among the trachytes some have been found con- 

 taining augite instead of hornblende— a curious and novel 

 fact which establishes an analogy between these tertiary 

 masses and some old syenites of Tyrol and Norway, in 

 which G. von Rath has lately shown that augite replaces 

 hornblende. The author partly following von Richthofen 

 divides the rhyolites into (i) Nevaditc or granitic 

 rhyolite ; (2) Rhyolite proper, including the felsitic and 

 porphyritic varieties, of which he has found among 



the rocks of the Fortieth Parallel no fewer than sixteen 

 well-defined types ; and (3) Hyaline rhyolite, including 

 the glassy and half-glassy varieties, obsidian, pitchstone, 

 pumice, S:c. With the exception of some varieties in the 

 eastern part of the region, all the basalts met with in the 

 course of this survey prove to be felspar-basalts. Though 

 repeating in Western America the familiar characters of 

 the basalts of Western Europe they contain some varieties 

 which merit a special subdivision. These are marked by 

 (i) the invari.able presence, though in small quantity, of 

 sanidine, (2) the general absence of olivine, (3) the 

 abundance of the glassy microlltic base, (4) the occa- 

 sional presence of hornblende, (5) a high proportion of 

 silica, (6) the dusty character of the included apatite. 

 A petrographer who admits such wide departures from 

 the normal type of a species must not be surprised at 

 those who would further seek to unite some of his species 

 which hai'dly differ from each other so much as these 

 varieties of basalt do. 



The Report is illustrated by twelve quarto coloured 

 plates. For beauty of execution nothing has appeared 

 like them since those of the lamented Vogelsang. They 

 have been executed at Leipzig, under the author's own 

 eye, and are evidently as faithful as they are vivid and 

 artistic. Archibald Geikie 



OUR BOOK SHELF 



Results of tlie Aralo-Caspian Expedition. Fascicule iv., 

 38S pp., with seven lithographed plates ; and Fascicule 

 v., sixty-eight pages. (St. Petersburg, 1877.) [Russian.] 

 The fourth fascicule of this publication contains an im- 

 portant paper by the well-known Russian ichthyologist. 

 Prof. Kessler, on "The Fishes of the Aralo-Caspian 

 Pontic Ichthyological Region." After an introduction, in 

 which the author briefly sketches the geography of the 

 region, and makes a few objections to some statements of 

 Mr. A. R. Wallace as to the geographical distribution of 

 fishes, Prof. Kessler describes forty-three new species 

 and varieties of fishes of the region, and twenty- four other 

 species, the previous descriptions of which were incomplete. 

 These descriptions, being the result of very elaborate 

 researches, ara based on extensive collections obtained by 

 the members of the expedition, and by previous explorers. 

 The new species are illustrated by seven plates. The 

 second part of the work is a systematic catalogue of all 

 fishes known to inhabit the region, with notes as to their 

 geographical distribution. 



The third part deals with the general conclusions 

 arrived at by the author as to the geographical distribu- 

 tion of species, the relations of the Aralo-Caspian ichthyo- 

 logical fauna to the faunas of the neighbouring basins, the 

 distribution of species in different waters of the region, 

 the zoological characteristics of the fishes inhabiting it, 

 and their genealogical relations, their mode of life, and 

 some remarks on the geological history of the region. 

 These conclusions (some of which have already been 

 noticed in Nature) will certainly be of great interest to 

 the zoo-geographer, and their importance is much 

 enhanced by the usual caution of M. Kessler's statements. 

 The work is altogether an important acquisition to ichthyo- 

 logical literature in general, all the more that it deals with 

 countries very imperfectly known until now. 



The fifth fascicule of the work contains two papers by 

 M. Aldnitzin : " On the Sweet Water Springs on the 

 Shores of Lake Aral," and a "Sketch of the History of 

 the Islands of that Lake," the former containing some 

 interesting information as to the distribution of water 

 in sandy steppes. 



