November 19, 1886 J 



SCIENCE. 



465 



ever, must be made by a separate instrument, — 

 by the barometer, if great accuracy is not required, 

 or by spirit-level, if the barometer does not meet 

 the requirements. The stadia instrument measures 

 distance, direction, and relative height. In this 

 combination lies its superiority to other instru- 

 me^its for traverse surveying. It is not, however, 

 as rapid, as cheap, or as accurate in its measure- 

 ments as the odometer. The method is new to 

 many surveyors, and is attractive from its novelty. 

 Extraordinary claims are made for it in regard to 

 accuracy, which are scai-cely to be realized in 

 practice. 



Until recent years, the vertical element of topog- 

 raphy has received little attention. If recog- 

 nized at all, it has been represented qualitatively 

 only, by means of shading, either by hachures, 

 crayon, or brush work. The U. S. coast and 

 geodetic survey, however, from its inception, has 

 mapped the relief quantitatively, by means of 

 contours, but, strange to say, has in nearly all its 

 published maps failed to reproduce this material, 

 but has represented relief by hachures. At pres- 

 ent the importance of showing the relief quanti- 

 tatively is becoming recognized, and most modern 

 maps have a \ea-tical as well as a horizontal scale, 

 the relief being represented by contours. Al- 

 though this reform is now well advanced, and 

 although the methods of surveying the vertical 

 element are well matured, there is still much mis- 

 conception among engineers in regard to these 

 methods. Many engineers can imagine no other 

 way of mapping the contours of an area except 

 that of taking up each contour and tracing it in 

 all its convolutions. That contours can be sketched 

 with sensible accuracy over a wide area, providing 

 the sketch be corrected by the measurement of 

 the heights of a dozen or more key points, they 

 are slow to believe, and the fact that the U. S. 

 coast and geodetic survey uses this means of locat- 

 ing contours, only lessens their faith in the in- 

 fallibility of that organization. 



Among all the treatises and text-books upon 

 topographic surveying recently published there is 

 not one which treats the subject in a comprehen- 

 sive manner. These books, in so far as they relate 

 to field work, discuss little besides the geometi'ical 

 part of the topographer's work, — the simplest and 

 in many respects the least important, and always 

 the most easily learned part of his profession. The 

 artistic part of the field work is either ignored 

 entirely or is treated as of very little importance. 

 This is perhaps due to the difficulty of describing 

 the almost infinite variety of the work, as it 

 changes with each day and with every square 

 mile. Moreover, it is a subject which can be 

 treated with much greater facility by means of 



object lessons in the field than by books. The 

 aphorism that ' topographers are born but not 

 made,' may have something to do with this lack 

 of facilities for making them. Another general 

 criticism upon these books is, that, of the vai'ioiis 

 methods of location, they treat only of location by 

 traverse, and the impression constantly conveyed 

 to the student is, that topographic work is uni- 

 versally done by means of traverses. A miscon- 

 ception regarding the use of the plane table ap- 

 pears to exist in the minds of most engineers who 

 have written upon topographic surveying. They 

 appear to regard the plane-table solely as a stadia 

 instrument, and criticise it from that point of 

 view alone. There is no method of surveying to 

 which this instrument is not applicable, and, for 

 most kinds of work, it is the simplest, most con- 

 venient, and most accurate instrument in use. 

 Again, these books are very unsatisfactory regard- 

 ing the construction of the vertical element of 

 maps. The impression conveyed by the treat- 

 ment of this subject is, that contours should be 

 traced upon the ground, a method never employed 

 upon geographical surveys, as stated above. 



Another generic feature of these books which is 

 worthy of attention is, the great number and com- 

 plexity of the conventional signs which they de- 

 scribe. In general topographic maps it is desirable 

 to keep the number of such symbols down to the 

 smallest possible, consistent with the amount of 

 information which the map should contain : first, 

 in order that the maps may be easily read ; and 

 second, that they may be easily kept up to date. 

 Another notable omission is, the want of consider- 

 ation of the s(;ale of maps as affecting the charac- 

 ter of the work, — a matter which involves the 

 degree of accuracy and of detail necessary to I e 

 obtained in the survey, and, consequently, the 

 cost of the work. It appears to be assumed that 

 a survey is a survey, which may be plotted upon 

 a larger or a smaller scale, without any regard to 

 the quality of the material obtained. In point of 

 fact, there is no more important question in the 

 economics of map-making than that of scale, and 

 the right proportionment of the work to the 

 adopted scale. It is in this direction, more than 

 any other, that improvement is to be expected in 

 the conduct of work. 



Professor Haupt's ' The topographer ' ' is the 

 most comprehensive and satisfactory of the recent 

 manuals on topographic surveying. Still, while 

 treating with great fulness of traverse surveying, 

 it ignores other methods of location. It makes an 

 attempt to treat of sketching, but without much 

 success. The chapter upon relief, drainage systems, 



1 The topographer, his instruments and methods. By 

 Lewis M. Haupt, A.M., C.E., Philadelphia, Stoddart, 1886. 8°. 



