E. DoBSON. — State of Applied Science in Canterlury. 131 



is made for a road, the wind soon lays prostrate the decayed trees, as well 

 as all those which may happen to have grown with an outward inclination. 



So many breakages have taken place from this cause, that it would 

 appear to be a safer method of construction to erect the telegrajih wires in 

 the forests at a short distance from the road clearings, merely removing 

 enough of the undergrowth to allow of the wires being strained from tree 

 to tree. Of course, the lines would be somewhat crooked, and the points of 

 support greatly multiplied, but the risk from falling timber would be reduced 

 to a minimum. 



The other special cause of breakage lies in the necessity for fixing the 

 telegraph poles in many places in the shifting shingle of the river beds. 

 The only remedy for this appears to be to sink the foundations of the points 

 of support below the limits of the shifting shingle, either by driving in piles 

 or by bedding the posts in blocks of concrete, and to diminish their number 

 as much as possible. 



By elevating the points of support to such a height that there shall be 

 no undue strain, the Provincial Telegraph Manager, Mr. Gr. Bird, has suc- 

 ceeded in erecting with common No. 8 wire, and maintaining without 

 accident, spans much larger than those commonly used. 



The following are the largest spans in the Hokitika line : — 



Eiver Porter ... ... ... 1,848 feet. 



Yalley of the Seven Springs ... 2,122 „ 



Valley of the Broken River ... 3,498 „ 



In the latter instance, the telegraph poles are placed on the clifEs at the 

 edge of the valley, which is so deep that there was no difilculty in giving a 

 safe curvature to the Avire ; and although the action of the wind on this 

 immense span is considerable, the ware appears perfectly equal to the strain. 



Although the Hokitika line is carried across two high ranges, the passes 

 through which are covered with snow for several months in the year, very 

 little inconvenience has been experienced from this cause ; but the working 

 of the line has been occasionally delayed, in the winter months, by the 

 thawing of the frozen snow w^hich has accumulated round the insulators, by 

 the heat of the sun, thus causing a current to earth, the insulation being 

 restored in the afternoon, as soon as the temperature fell below freezing 

 point. 



The construction of the western portion of the line to Hokitika was 

 attended with many serious difficulties. Upwards of fifty miles were through 

 forests inaccessible to horses, and intersected by dangerous rivers ; whilst 

 the weather in the Alpine ranges was so severe that during one month there 

 were only nine days on which it was possible to work. 



