ADVANTAGES OP MEANDER CONTROL. 179 



Unsupported triangulation affords few tie-points ; stations and intersections 

 are fixed without appreciable error to the scale of the map, but roads, streams 

 and contours, if the last be employed, are generalized according to the hand- 

 writing of the topographer rather than to the character of the topography. 

 The geologist who is obliged to use such a map should be fitted to locate him- 

 self by direct reference to the geometric control, and he should check the 

 generalizations of the map by such references. 



A meander line fitted to a scheme of triangulation supplies tie-points 

 within a belt of varying width. If it follows a road or stream each change 

 of direction provides a tie-point, and the elements of relief within the topog- 

 rapher's view are fixed usually beyond his power to generalize out of recog- 

 nition. Thus the number of tie-points increases much faster than the num- 

 ber of miles of meander run ; and the value of the map is rapidly augmented 

 as the net-work of meander lines is made finer. Thoroughly satisfactory 

 maps can be made by this method. The first example of this class of work 

 which came to my notice was the Greenville, Tennessee, atlas sheet of the U. 

 S. Geological Survey series ; it represents a thousand square miles of the 

 valley of Tennessee, where the present relief is a dissected base-level in lime- 

 stone, overlooked by strike ridges of sandstone and shale. All the roads 

 were meandered, the total distance being about 1,200 miles, a season's work 

 for one topographer. The southeastern corner of the sheet is mountainous 

 and without roads. Here the topographer was confined to sketching to fill 

 in his triangulation, and the resulting map is so inadequate that the geologist 

 was obliged to correct the base by meander lines run on foot. Other maps 

 of this desirable character have been and are being made by those topo- 

 graphers who appreciate the possibility of putting character into their work. 

 Such men raise their profession from the dead-level of mechanical generali- 

 zation to an art which expresses important geographic truths. And these 

 geographic facts are but the latest expression of geologic processes, which it 

 is the province of the geologist to interpret. But the topographic artist has 

 been a rare being, and while we may felicitate ourselves upon the prospect 

 of his becoming more numerous, we still have to work with the inartistic 

 product. 



Procedure with an inadequate Base. 



The general Question. — How can the geologist best proceed in the field 

 with a map which does not afford tie-points for his observations; or, in other 

 words, given an inadequate base, what method of field work leads most 

 satisfactorily to the development of a geologic map ? To this question thus 

 broadly stated no intelligent answer can be given. Account must be taken 

 of the geologic problem, of the aspect of its presentation and of the character- 

 istics of the geologist. The student of crystalline rocks, accustomed perhaps 



