318 



ENGINEERING. 



daringly undertook to close a door in the drift- 

 way 330 yards from the shaft. The distance 

 was too great for the ordinary appliances of 

 air-pipes, and for 85 minutes he was entirely 

 cut off from any communication with the sur- 

 face. He closed the door, and subsequently 

 other openings were closed, so that eventually 

 the spring was confined, upon which the wells 

 and streams resumed their natural flow. An- 

 other rush of water occurred on the English 

 side under the river, but this was stopped by 

 puddling with clay. The danger from water 

 was never lacking, and several other serious 

 disasters of this kind were only prevented by 

 watchfulness. In spite of all vigilance anoth- 

 er bad break occurred, and 27,000 gallons per 

 minute burst into the tunnel. The doors pro- 

 vided for such emergencies were closed by 

 Lambert, with less danger this time, since the 

 distance was only 150 yards from the shaft, 

 and air-pipe communication could be main- 

 tained. The dimensions of the main tunnel 

 are 26 feet wide and 20 feet from rails to 

 crown. The invert arch has a radius of 21 

 feet 6 inches. Frequent recesses are provided 

 for workmen and tools. The brick-work was 

 largely constructed from bricks made on the 

 spot by the contractor from clay found in 

 course of excavation. The product resembled 

 the blue brick of Staffordshire. The great 

 length of the tunnel necessitates no less than 

 fourteen shafts for pumping and ventilation, 

 and powerful fans are provided to accelerate 

 the air-movement. The engineers in charge of 

 the work were Sir John Hawkshaw and Mr. 

 Charles Richardson, and the contractor since 

 the outbreak of the big spring was Mr. T. A. 

 Walker, of Westminster. The total cost of 

 the tunnel and its accessories was not far from 

 $10,000,000. 



Big Bend Tunnel. Feather river, California, 

 has afforded, since the early mining days, a rich 

 field for gold- seekers, and the accessible parts 

 of its bed and banks have been pretty thor- 

 oughly worked over, with generally remunera- 

 tive results. In Butte County, however, the 

 river runs through a wild canon, following a 

 semicircular course for fourteen miles, the cur- 

 rent being so swift and the banks so precipi- 

 tous that prospectors have been able to sample 

 the deposits only under especially favorable 

 conditions. The result of these casual exami- 

 nations indicated that the whole bend was rich 

 in gold, and surveys made in 1882 showed that 

 a tunnel 12,000 feet long would carry the water 

 of the river from a point above Big Bend to 

 Dark Canon, down which they would flow, 

 and rejoin Feather river some distance below 

 the bend. This would of course open the river- 

 bed for mining operations. Work was begun in 

 November, 1882, and the tunnel, with a cross- 

 sectional area of 160 square feet, was practically 

 finished in April, 1886. The heading was be- 

 gun at the lower end and run upward at a 

 grade of 29 '7 feet to the mile to within 300 

 feet of the upper end when the remaining dis- 



tance was utilized for a steep grade to secure a 

 high velocity for the incoming current. As 

 was anticipated, timber-work was nowhere re- 

 quired, the whole mountain being solid rock, 

 mostly slate, with occasional stringers of quartz 

 and granite, and about 200 feet of very hard 

 dorite. In several places gold-bearing rock 

 was penetrated, yielding $8 to $14 per ton. By 

 the end of 1883, nearly 4,000 feet had been 

 finished, and the monthly average varied from 

 300 to 400 feet, according to the quality of the 

 rock. During the greater part of the time three 

 shifts of 12 men were employed, each work- 

 ing 8 hours. Each shift comprised 1 foreman, 

 4 drill-men, 4 assistant drill-men, 1 powder- 

 man, 1 car-man, and 2 laborers. The perma- 

 nent outside force consisted of 2 blacksmiths, 2 

 helpers, 2 engineers, and a number of laborers 

 varying with the requirements of the work. 

 The original plant was a No. 4 Burleigh air- 

 compressor, driven either by steam or water; 

 an air-tank, 4 by 16 feet; a No. 3 Knowles 

 pump ; a 2 by 8 Llewellyn heater ; an 8-foot 

 Knight water-wheel; a Buffalo drill-carriage, 

 mounting 4 drills, and a tubular boiler 5 by 16 

 feet. Subsequently there were added 4 Bur- 

 leigh tunnel-drills, a No. 4 Clayton duplex air- 

 compressor, and a No. 5 Baker blower and en- 

 gine to run it. The water-power was brought 

 from Dark Cafion through a 11-inch iron pipe, 

 having a vertical fall of 275 feet. The blower 

 was used exclusively to draw smoke and bad 

 air out of the near advanced heading through a 

 pipe, while the air-compressor delivered fresh 

 air in the face of the heading. The two ma- 

 chines were set to work about fifteen minutes 

 before each blast, and kept running until the 

 debris was cleared away and the drills again set 

 in motion, when the compressed air used for 

 driving the drills afforded enough fresh air. A 

 two-foot track was laid through the tunnel and 

 the debris hauled out by mules. It was esti- 

 mated that this tunnel would carry the whole 

 volume of Feather river during nine months of 

 the year, but experience showed that it was 

 not large enough to do all that was expected of 

 it. During the progress of the tunnel, exten- 

 sive preparations were made for working the 

 river-bed and bringing supplies from Oroville; 

 a dam was built at the head of the tunnel, and 

 roads cut along the river-bank and over the 

 mountain wherever needed. The unexpected 

 surplus of water interfered somewhat with 

 working the river-bed, but rich deposits of gold 

 were found wherever the hydraulic engines 

 could be set to work. 



Tunnel at Stockholm. The capital of Sweden 

 is divided in its most populous part by a ridge 

 of rock and gravel about seventy feet high and 

 nearly eight hundred feet wide. Capt. Lind- 

 mark several years ago obtained permission to 

 tunnel this hill for the use of foot-passengers, 

 he to levy a charge of two ore (about half a 

 cent) per passenger, for fifty years ; the tunnel 

 after that to revert to the municipality. The 

 project was strenuously opposed by owners of 



