64 A MANUAL OF TOPOGRAPHIC METHODS. 



them. < hi the other hand, in a densely wooded region such as the Cumber- 

 land plateau, when- the summits have approximately the same elevation, the 

 selection of stations is an extremely difficult matter, requiring- great ability 

 and experience and involving an immense amount of labor. In such a region 

 the chief of party finds it necessary to travel great distances, visit many hills, 

 and even has to climb to the summits of the highest trees, in order to select 

 intervisible stations. 



The selection of stations must be kept in advance of the reading of 

 angles, hut it is not advisable to keep it too tar ahead, on account of the 

 danger of the destruction of signals before angles have been read upon them. 

 Therefore, the chief of a party finds it necessary to alternate between the 

 two kinds of work, selecting and preparing three or four stations, then re- 

 turning and measuring the angles. 



When it is necessary to use heliotropes, the party has necessarily to be 

 increased bv one man for each heliotrope employed. The proper manage- 

 ment of such a party then becomes a matter calling for the exercise of much 

 judgment on the part of the triangulator. If it is convenient for the chief of 

 party to place each heliotroper before observing angles, and to show them 

 where to direct their instruments, men of ordinary intelligence may be em- 

 ployed and the work is one calling rather for time than skill. Where, how- 

 ever, the part}- is moving almost daily, the observer and heliotropers occu- 

 pying a different station nearly every day, as is possible in the dry and clear 

 atmosphere usually prevailing in the West, the chief of party has to arrange 

 a schedule for each man, showing the order in which he is to occupy the 

 stations and in what direction he is to flash from each. The heliotroper 

 must be a man having some topographic and technical skill, so that he may 

 find his point, set up on center and direct his flashes to the right place, 

 besides exercising a goodly amount of common sense judgment. A simple 

 code of signals being agreed upon, it then becomes an easy matter for the 

 triangulator to let the heliotropers know that the work is completed, when 

 they at once move to the next designated station. 



