52 



SCIENCE. 



[Vol. X. No. .234 



comparatively few of them would be selected as key points for 

 location purposes. Even with this qualification, caution is needful 

 in making comparisons between different pieces of work. The 

 undulating, sparsely settled Texas area, and the monotonous 

 plateaus of Arizona, must not be contrasted with western Massa- 

 chusetts, where abrupt hills and an abundance of cultural features 

 require a large number of locations, and render it practicable to 

 make them. 



Third, the distribution of locations is a matter of no less impor- 

 tance than their number. To illustrate the degree of uniformity of 

 their distribution, the following cuts are presented. Fig. i repre- 

 sents the geometric control of an atlas sheet, from the plane-table 

 work of Massachusetts ; and Fig. 2, a sheet from the traverse work 

 in the same State ; the lines representing the lines of traverse, and 

 the triangles the triangulation points which serve to check the 

 traverses. Fig. 3 represents the control of an Appalachian sheet, 

 showing triangulation stations, locations by intersections, and traverse 

 lines. It will be seen that the distribution is quite uniform. It will 



or less idealized. No two men will generalize an area of country, 

 to adapt it to the scale, in precisely the same way. Some will 

 generalize more, others less ; some will omit this feature, others 

 that ; and they will merge minor features in various ways. The 

 smaller the scale, the greater is the generalization, and, conse- 

 quently, the greater room for differences in the work of different 

 topographers. 



The cost of the work is influenced by a great variety of condi- 

 tions, the principal of which are the following : — 



a. The Scale. Other conditions being similar, the cost increases 

 with the scale, at a rate somewhat less than a geometric ratio, 

 i.e., if the scale be doubled, the cost is somewhat less than four 

 times as great. 



b. The character and amount of the relief, drainage, and culture. 

 The greater the relief, and the greater its detail, the more the work 

 will cost. Work in a thickly settled country, containing many 

 settlements, roads, etc., necessarily costs more than that in one of 

 sparse settlement. 



be noticed, further, that in a country composed of an alternation of 

 mountain and valley, as the Appalachian region, most of the loca- 

 tions by intersections are upon the mountain ranges, while the 

 traverse lines are mainly found in the valleys. 



Fourth, concerning the quality of the sketching, little can be said. 

 There are no means of verifying this work, except by an examina- 

 tion of it on the ground. It is in this part of the work more than 

 any other that the personality of the topographer appears. It is 

 here that his artistic sense, and his power of making his pencil 

 record faithfully his conceptions, comes into play. It is scarcely 

 necessary to add that no two topographers will sketch an area pre- 

 cisely the same. There will be differences in seeing, and differences 

 in drawing, just as there are differences in handwriting. Every 

 map, whatever its scale, is a reduction from nature. This reduc- 

 tion necessarily implies a certain amount of generalization. Certain 

 features must be omitted, others merged into larger features, so 

 that no map is or can be an exact miniature. Every map is more 



c. The degree in which a country is covered with forests. This 

 element not only interposes obstacles and causes delays in the 

 prosecution of work, but often necessitates the adoption of slower 

 and more expensive methods of work. 



d. Atmospheric conditions. This includes stormy weather, haze 

 and smoke, which, being especially prevalent during the field-season 

 in some localities, unduly increase the cost of the work. 



e. Length of field- season. At the opening of each field-season, 

 it is necessary to devote some time and money to outfitting the 

 parties and starting field-work. This is in the nature of a plant or 

 investment for the season. Once at work, the expense is not great.. 

 It costs little more to keep a party in the field for six months than 

 for three months, while the amount of work done by the party is 

 doubled. Therefore, long field-seasons are more economical than 

 short ones. 



The following table shows the cost of the work in the several 

 areas under survey, including field and office expenses : — 



