108 The N.Z. Journal of Science and Technology. [Mar. 
Table I. 
Span. 
Maximum 
Sag in 
Still Air. 
Distance from Pole at which Wire drops. 
5 Feet. 
7 Feet. 
9 Feet. 
Links. 
Feet. 
I 
400 
3-2 
. . 
• • 
500 
5-3 
• • 
, , 
600 
7-25 
140 
300 
700 
9-8 
112 
181 
270 
800 
12-8 
91 
135 
190 
900 
16-0 
78 
114 
156 
1,000 
20-0 
70 
100 
134 
1,200 
29-0 
56 
80 
106 
1,400 
39-0 
48 
68 
88 
1,600 
52-0 
41 
58 
73 
1.800 
65-0 
37 
52 
67 
2,000 .. .. 
1 
80-0 
33 
47 
60 
Columns 3, 4, and 5 are useful to test clearance at a point near the pole. 
Table II. 
Distance. 
Minimum Slope 
required to give 
Clearance. 
Maximum Slope 
required for 
Stability. 
Links. 
100 
5° 18' 
- 0° 19' 
200 
1° 37' 
- 0° 41' 
300 
0° 00' 
- 1° 06' 
400 
- 1° 17' 
1° 34' 
500 
- 2° 17' 
2° 06' 
600 
- 3° 11' 
2° 43' 
700 
- 4° or 
3° 27' 
800 
- 4° 49' 
4° 16' 
900 
- 5° 36' 
5° 03' 
1.000 
- 6 C 22' 
5° 53' 
1,200 . 
- 7° 50' 
7° 45' 
1,400 
- 9° 13' 
8° 55' 
1.600 
- 10° 38' 
10° 26' 
1,800 
- 12° 00' 
11° 48' 
2,000 
- 13° 24' 
13° 14' 
If we have a doubtful point between two poles, measure the slope and 
distance from each pole. Then compare the change of slope with the sum 
of the slopes corresponding to the respective distances in column 2 and then 
in column 3. If the change of slope exceeds either, the pull will always 
be upward, and clearance is assured and a pole saved. If the change of 
slope is less than either, the pull is always downwards, when a pole becomes 
necessary. Should the change of slope lie between the two values the 
pull will be sometimes up and sometimes down, in which case we have to 
provide anchorage. 
