3. Section and perspective view showing relations of surface features to the different kinds of rocks and the structure of the beds 30 4. Sections of coal beds 31 5. Diagram illustrating method of projecting a map 44 6. Methods of expressing relief by contour lines, by hachures, by shading on stipple board, and by a brush drawing 49 7. Designs for bar scales 60 8. Method of making a bar scale for a map of unknown scale 60 9. Map bearing six areal line patterns 62 10. Diagram showing method of marking maps for reduction or enlargement (for record) 64 11. Structure section showing method of determining the succession of folds 65 THE PREPARATION OF ILLUSTRATIONS FOR REPORTS OF THE United STATES GEOLOGICAL SURVEY. By John L. Ridgway. PART I. PREPARATION BY AUTHORS. INTRODUCTION. There has been an obvious need in the Geological Survey of a paper devoted wholly to illustrations. No complete paper on the character, use, and mode of preparation of illustrations has been published by the Survey, though brief suggestions concerning certain features of their use have been printed in connection with other suggestions pertaining to publications. The present paper includes matter which it is hoped will be of service to authors in their work of making up original drafts of illustrations and to draftsmen who are using these originals in preparing more finished drawings, but it is not a technical treatise on drafting. The effectiveness of illustrations does not depend entirely on good drawings nor on good reproduction; it may be due in large part to the inherent character of the rough material submitted. If this material is effective or striking the finished illustrations, if well made, will be equally effective and striking. Each step in the making of an illustration--first the preparation of the author's original or rough draft, next the final drawing, and last the reproduction--is closely related to the others, and each is dependent on the others for good results. If the material has been well handled at all three steps the resulting illustration should be above criticism; if it has been poorly handled at any one of the three the effectiveness of the illustration is either impaired or ruined.