IRLF i Division * Range :...,.... Received Ll Ally """vanwrv o OF FRONTISPIECE Sccde 1% inches to 1 GAULT. ht UPPER GREEHSAND CHALK i?. READING BEDS .ALLUVIUM BRICK -EARTH GRAVEL. FIELD GEOLOGY. BY W. HENEY PENNING, F.G.S., Geologist, H.M. GEOLOGICAL SURVEY OF ENGLAND AND WALES. WITH A SECTION PALAEONTOLOGY. BY A. J. JUKES-BEOWNE, B.A., E.G.S, H.M. GEOLOGICAL SURVEY. LI p> ii \ n \ UN1\ KKS1TY OF CALIFORNIA. LONDON :z BAILLIEEE, TINDALL, AND COX, 20, KING WILLIAM STREET, STRAND. PARIS: BAILLIERE. MADRID: BAILLY-BAILLIERE. (All Eights reserved.) Q E 4 5 THIS WORK 3E0 Qfttciionzttl TO MAEIANNE, THE WIFE OF THE AUTHOR. PREFACE. THE first idea that suggested itself to me, in regard to a work of this kind, was to publish a few plain instructions for drawing geological boundary-lines, a practical matter which seemed to have been somewhat neglected, although it is of considerable importance. But there is an almost imperceptible transition from mapping rocks, which appear at the surface of the earth, to tracing those that are beneath, and from defining the extent of a formation to the determination of its history, as expressed in its lithological character and fossil re- mains. The idea, therefore, while being realised, expanded to much beyond its original dimensions, still there is scarcely any portion of the book in which the matter might not, with advantage, be enlarged. It has, how- ever, been thought advisable to issue, as it is, this first edition, and leave for a second (should it ever be re- quired) any further extension. There are so many subjects of which a knowledge is -an advantage in geological surveying, that it is difficult VI PEEFACE. to say what ought not to be included in a book on Field Geology. The object aimed at has been to include herein those that are absolutely necessary, in as small a com- pass as is consistent with the purpose in view. My colleague, Mr. Jukes-Browne, was good enough to undertake the section on Palaeontology, at a time when, unfortunately, his state of health was not as good as could be desired. For this reason the list of charac- teristic fossils following his work was not prepared by him, and it is, perhaps, far from being as complete, and probably as accurate, as it would otherwise have been. The new rules for finding direction of true dip, when first published in the Geological Magazine for May 1876, gave rise to some useful criticism; it was then too late to make any alteration in the text or the figures,, but a footnote has been inserted to give the resulting modification. W. HENBY PENNING. CALDECOTE, GAMES. August, 1876. CONTENTS. PACK INTRODUCTION 1 PAET 1. GEOLOGICAL MAPPING. CHAPTER I. MAPPING AND INSTRUMENTS. Maps Contour Maps Compass and Protractor Ham- mer, Pick, Spud, &c. Scales Tracing Boundaries General Propositions - 5- CHAPTER II. MAPPING {continued). Examples of Tracing Boundaries Memoranda Travers- ing Symbols Drift Deposits - II PAET II. SECTIONS. CHAPTER I. GEOLOGICAL SECTIONS. Dip Strike Clinometer To find Direction of Dip To find Amount of Dip Table of Dip, Depth and Thick- nessExposed Sections Notes - - 38 Vlll CONTENTS. CHAPTER II. HORIZONTAL SECTIONS. Datum-level Bench-marks Levelling, ly Aneroid, by Level Level-book Plotting, from Heights Levelling, lyy Theodolite Level-book Plotting, from Angles Filling in Geology Apparent Dip 61 PART III. LlTHOLOGY. CHAPTER I. DETERMINATION or ROCKS AND MINERALS.. Texture Structure Fracture Lustre Hardness and Effervescence Specific Gravity Reactions in the Wet Way Blowpipe - 87 CHAPTER II. DETERMINATION OF ROCKS AND MINERALS (continued). Table of Tests, in the Field, at Home Metals Tests- Microscope Chemical Analysis List of Books of Reference Peculiarities of Structure, Concretions, Sliclcensides Note on Metamorphic Rocks Cabinet Specimens 100 PART IV. PALAEONTOLOGY. CHAPTER I. Introduction Nature of Fossil Remains Review of Ani- mal Kingdom Mode of occurrence of Fossil Remains Petrifaction - 122 CHAPTER II. Method of Collecting Fossils Examples - - - 133 CONTENTS. IX CHAPTER III. Preservation, Naming, and Arrangement of Fossils Value of Paleeontological Evidence Evidence of Physical Conditions - - 144 CHAPTER IV. Characteristic Fossils Table of Fossils - - 157 PART V. CHAPTER I. Survey of Older Rocks Boundaries and Faults Down- throw Vertical Section Eruptive RocksVeins - 202 CHAPTER II. Geological Generalisation and Practical Results "Water- supply Soils - -214 ILLUSTRATIONS. GEOLOGICAL MAP coloured - Frontispiece. PAGE Figure 1. Compass and Clinometer 7 2. Protractor, upper side - 9 3. Hammer, Pick, and Spud, combined - 11 4. Protractor, under side, as Scale - 12 , 5. Area Surveyed, First Slip 10 6. Second Slip 22 7. Third Slip - 24 8. Fourth Slip 20 9. Methods of Traversing - - 30 10. Clinometer 40 " I Diagrams for finding Direction of Dip - 43 ., 12. 3 -jo 44 1) id' 55 55 55 55 14. Example of finding Direction of Dip, by Dia- gram - 45 " ' | Diagrams for finding Amount of Dip 17. Diagram for finding Amount of Dip and its Direction - 48 18. Inaccessible Cliff, to find the height of - 80 19. Horizontal Section - 83 20. Diagram for finding Apparent Dip - 85 20cr. Cast and Impression - - 132 21. Area Surveyed Palccozoic Rocks - 204 22. Section across Fig. 22 210 23. Vertical Section - - 212 LIBRARY UNIVERSITY OF CALIFOUXIA. FIELD GEOLOGY. INTRODUCTION. IT may fairly be claimed for Geology that its advance has been more rapid than that of any other science. From the time of William Smith the Father of English Geology until now the number of those who take interest in the subject has been steadily increasing. Every year sees the birth of some new periodical devoted to Geological Science ; every list of new books is sure to contain the name of one or more bearing directly or indirectly on the questions with which it deals, and it possesses already a most comprehensive literature. It plays a prominent part in University and and other public examinations, where, until recently, it was all but unknown; and it guides, as it ought to guide, the direction of mining and other practical operations. "With many the study is taken up as an amusement or a pastime, and is found to possess a fascination pecu- liarly its own ; it opens up to the more philosophical student a fair field of investigation ; and presents to all many interesting physical problems for thought and speculation As the number of geological students increases, the 1 FIELD GEOLOGY. greater is felt to be the need of a Manual which shall teach the practical procedure in the field and elsewhere. A great majority of the manuals of Geology, although excellent as guides to a theoretical knowledge of the science, do not sufficiently describe the methods of obser- vation in the field. Without such proper method much time is wasted, many results that otherwise would have been valuable are entirely lost, and the student finds that his labours do not yield to him a proportionate amount of beneficial knowledge. To facilitate the acquirement of such knowledge, this work has been published not as containing very much that is original, but as embodying in a small compass practical directions and suggestions which are to be found here and there only in more important works. The object has been to bring them with some additions which are the result of practical experience into a form which shall be at once portable and adapted to special reference. If we would make a series of drawings that shall shew the geological structure of any district, it is not sufficient that we are versed in theoretical geology, nor even that we can walk into a quarry and say, " This is a Lime- stone," or a "Sandstone" as the case may be and "it belongs to this or that Formation." We must be able to trace out its boundary, to shew the area that it occupies, and to ascertain the angle at which it dips be- neath the surface. When these points are determined in regard to a series of strata, we have a geological Map, or surface projection and aided by our notes, we can construct therefrom a geological Section, which shall shew the underground extension of the rocks, their thick-