﻿126 Form oj a Suspended Wire or Tape. 



conditions, but unfortunately this intention was not carried out. 

 The agreement, however, is close enough to show that no 

 blunder has been made in working out the theory. 



The writer also made experiments to test the ordinary sag 

 formula while he was engaged in measuring in 1900 a base- 

 line with a J-inch tape of about the same thickness -fa inch 

 and 500 feet long. This was supported during the mea- 

 surement at intervals of 50 feet, and stretched by an end 

 tension of 20 lb. In the tests supports were placed also at 

 every 5 feet, and the movement of one end of the tape was 

 observed when it was supported at these and various other 

 intervals. The writer has not the actual figures at hand, but 

 the agreement, speaking from memory, was nearly perfect 

 between observation and calculation, the difference between a 

 change from 5 to 50 feet intervals in the supports being 

 about r J inch. Such a test includes of course the effect of 

 bending. 



It was for long the writer's desire to test the sag formulae 

 on slopes of high magnitude, say 45° to 60°, with a good 

 length of tape in sag and with various tensions, in order to 

 see practically where the limits of applicability of the formulae 

 lie, but unfortunately he was unable to carry out this intention 

 before retiring from the Malay States Survey. He gives the 

 following sketch of how he intended to proceed in case any 

 other surveyor may have the desire and opportunity of making 

 the tests. 



The tests should be made with as long a tape as possible; 

 and as wire can be obtained in continuous lengths of 1000 feet 

 and more, there is no difficulty in getting a good long con- 

 tinuous and presumably homogeneous tape. The chief diffi- 

 culty would be in finding a site, which would have to include 

 either a tower or precipitous hill or cliff, say 500 feet 

 above a plain where base-lines could be measured. Two or 

 three base-lines should be measured on this plain giving 

 slopes from 45° to 60° from their ends with a point on the 

 summit; and it would be well to have each in two sections, 

 to give a check in the calculated distances to the latter. The 

 base-lines should be measured with the tape to be used on the 

 slopes, and the station on the summit carefully triangulated 

 into. Very careful vertical angles should be observed reci- 

 procally if possible, so that the direct chord distances from 

 base stations to summit could be calculated with precision, 

 refraction being eliminated as far as possible. These calcu- 

 lated distances could then be compared with those given by 

 the tape used on the slope from base to summit directly, and 

 with various tensions. As there should be no interference 



