278 The Scottish Naturalist. 



chiton from the Upper Bala (Silurian) of Girvan, Ayrshire, by Henry 

 Woodward, F.R.S. (named here H. Grayiae). Abstract of paper in Tram. 

 Roy, Soc, Edinburgh (XXXII., pp. 359-388, with 2 plates), on The Old 

 Red Sandstone Volcanic Rocks of Scotland, by B. N. Peach and John 

 Home. " The authors observe that the most interesting feature connected with 

 the Old Red Sandstone formation in Shetland is the evidence of prolonged 

 vocanic activity in those northern isles. . . . The absence of any inter- 

 calations of sandstones, flagstones, or shales, save near the fault at Brei Wick 

 and Rooeness Voe, indicates that the subaqueous eruptions must have been 

 well nigh continuous for a time in that portion of the basin." 



REVIEWS. 



OUTLINES OF GEOLOGY.* 



Under this title Professor James Geikie has published a text-book for the use 

 of "junior students and general readers," and as, doubtless, many of the readers 

 of the Scottish Naturalist are inclined to place themselves in this class, they 

 may be glad to hear of a work which, while giving them all the latest informa - 

 tion, is not so abstruse as to deter them from the study. 



Beginning with the phenomena most familiar to him, the reader is made 

 acquainted with the various agents which have acted and are acting upon the 

 earth's crust, and is shown the various modifications brought about by the in- 

 strumentality of the atmosphere, of water in its various forms, and of animal 

 and plant life. Having studied these, a classification of the modern products 

 of these surface agents is presented to him ; a comparison made with the 

 rocks whose origin is supposed to have been similar ; and their practical 

 identity pointed out. 



From the more familiar phenomena the reader passes on to those less familiar 

 to him, and is introduced to the action of modern volcanoes and the products 

 resulting from them. The latter are shown to have all the essential characters 

 of the crystalline igneous rocks, and the deduction follows that these must have 

 had a similar origin. A description of some other crystalline rocks of a 

 different character is then given, with reasons for their origin. A chapter on 

 earth movements (earthquakes, &c. ) concludes the account of Dynamical 

 Geology. 



To Structural Geology, or that part of the science which deals with the 

 architecture of the earth's crust, six chapters are devoted, and the subject is 

 very fully considered and well illustrated. The effects produced by " faults " 

 upon outcrops at the surface are often rather puzzling to beginners. Dr. 

 Geikie explains the matter very lucidly, illustrating it by a series of original 

 models which will enable the student to readily comprehend the effects of the 

 action. From the value of these alone, apart from its other merits, the 

 " Outlines " ought to have a place in the library of every teacher, as well as 

 student, of geology. 



* Outlines of Geology : an Introduction to the Science. By J. Geikie, 

 LL.D., F.R.S. London : Stanford. 1886. 



