84 Renews — J. E. Marr's Stratigraphical Geology. 



11. — The PRiNcirLEs of Stratigraphical Geology. By J. E. 

 Marr, M.A., F.R.S. 8vo; pp. 304. (Cambridge: at the 

 University Press. Price 6s.) 



THE object of the present work is to give " some idea of the 

 methods and scope of Stratigraphical Geology " ; and the task 

 of the Stratigraphical Geologist, as the author clearly states it, is 

 " to recoi'd the events which have occurred during the existence of 

 the earth in the order in which they have taken place." The 

 subject is confined within tolerably strict limits, and it is treated 

 solely in its scientific aspect : we have no digressions on the form 

 of the ground, and no references to the economic applications of 

 stratigraphical knowledge. The nature of stratified rocks, the means 

 by which the order of succession is established, the method of 

 formation of the strata, the general conditions of each period, and 

 the correlation of the groups of strata, are the chief matters dis- 

 cussed ; and they are introduced in orderly succession after a short 

 account of the growth and progress of stratigraphical geology. 



The Cambridge School has acquired a deserved name for cautionary 

 teaching, and the author very fully places before his readers many 

 considerations that should be weighed before coming to definite 

 conclusions. In a useful chapter on " Simulation of Structures," 

 he draws special attention to pseudo-organisms, false ripple-marks, 

 diverse parallel structures, and crush-conglomerates or (as he prefers 

 to call them) fault-conglomerates ; and when the student comes to 

 deal with our stratified formations, with classification and correlation, 

 he will find more than enough of vexed questions over which to 

 ponder. 



One of the earliest of geological lessons is that all kinds of 

 sediment are being laid down in various aqueous areas, from coarse 

 detritus to deep-sea ooze, and that at the present day there is 

 a gradual change in the character of the fauna which exists at 

 ■various depths and at varying distances from the sea-margins. 

 When we come to the stratified formations which constitute the 

 bulk of the land on which we live, we learn that in those typical 

 localities which first gave name to the formations only limited 

 portions of the sea-bed of the period can there be represented. 

 Such names as Wenlock Shale, Inferior Oolite, Oxford Clay, Lower 

 Greensand, and London Clay indicate the lithological character of 

 formations at so-called typical localities. Subsequent study has 

 shown the presence on the same general horizon of strata of quite 

 different lithological characters, and different local subdivisions with 

 local names have come to be applied, such as the Denbighshire 

 Grits, the Lincolnshire Limestone and Northampton Sands, the 

 Spilsby Sandstone, Tealby Clay, etc. From such local phenomena 

 the geologist may seek to push his inquiries into the wide world 

 and study the general sequence of events, and he then requires 

 chronological terms of broad significance. 



It is now that the student has to face many and difficult problems 

 which are fairly and as fully as possible stated by the author. 

 While each great group of strata has a series of characteristic fossils, 



