DIRECT PLATTING IN THE NOTE-BOOK. 185 



follows : (1) to foresight by holding the compass in the right hand or on the 

 note-book at half arm's length and at a convenient height for alignment with 

 the object sighted and for reading the course ; the compass sights may be 

 closed or raised for this alignment and additional accuracy is perhaps obtained 

 by sighting the longer side of the note-book placed parallel to the compass 

 sights; (2) to record the foresight by drawing a line on the note-book page 

 at the observed angle from a meridian previously assumed ; a small horn 

 protractor is useful for this purpose, but it is only necessary for long sights, 

 such as those taken to locate distant points by intersections. It is easily 

 possible to estimate the angle of the observed course with sufficient accuracy 

 for sights of a quarter of a mile or less by bearing in mind the angles made 

 by the diagonals of various parallelograms; thus the diagonal of a square is 

 at 45°, that of a rectangle 2 x 3 is at 34° and 56°, that of one 1 X 2 is at 27° 

 and 63°, that of one 2 X 5 is at 22° and 68°, that of one 1 X 3 is at 18° and 

 72°, that of one 1 X 10 is at 6° and 84°, etc. These diagonals are easily 

 noted on the reticulated page. If a protractor is used it should have one 

 straight side with a scale on it; if there is no protractor a convenient ruler 

 can be made of a page of the note-book torn out and folded parallel to one 

 set of lines ; the folded edge will be straight and the lines at right angles to 

 it give the scale. It is obvious that errors of angular notation are more 

 serious the longer the sight laid down ; hence more care is needed on long 

 sights or on a large scale than on short sights or on a small scale. The 

 limits of scale which have been found desirable for field platting in the Ap- 

 palachian field are one and two miles to the inch ; the smallest scale on 

 which legible notes can be written is the best. As the meander thus noted 

 is extended, geographic and geologic notes fall into place along it. 



Summary of Methods. — In the foregoing paragraphs I have sketched three 

 ways in which members of the Appalachian division keep geologic field notes ; 

 first by direct notation on an adequate base, where such is available, second 

 by notation on a meander run with traverse plane-table and odometer or 

 pacing measurement, third on a meander surveyed without mounted instru- 

 ments and platted on the note-book page. It remains to indicate what the 

 use of such methods accomplishes. 



In any comparison of methods for the determination of efficiencies, two 

 factors must be considered for each method under like conditions. These 

 are quantity and quality of work. Under the conditions of stratigraphy, 

 structure and culture existing in the Appalachian province, the quantity of 

 W'ork which can be accomplished with graphic methods of keeping field 

 notes is best estimated by stating the number of miles of meander line that, 

 with topographic and geologic notes, can be platted daily. Using the 

 odometer attached to a buckboard with two horses and a driver, we estimate 

 the average product at 15 miles a day after two years' experience. Pacing 



XXVlII-BuLL. Geol. Soc. Am., Vol. 2, 1890. 



