GoODALL, — Blading at Ahiriri Bluff, Xapier. 551 



which could not be seen on account of the great cloud of dust that 

 had arisen. The material that fell into the sea caused a small 

 wave of about 5 feet high to roll off the shore. 



The estimated amount of spoil thrown down was 52,000 

 cubic yards, equal to about 87,000 tons in weight ; the work 

 effected was therefore about 12,180 times the weight of powder 

 used, the result being better than given in Professor Rankin's 

 work on engineering, where the average effective work is set 

 down at about 10,000 times. 



The cost of this blast was : — 



Blasting powder ... ... ... £526 



Mining and tamping ... ... ... 141 



Timber and carpentry ... ... 13 



Total £680 



Each cubic yard displaced, therefore, cost rather over 8d., 

 equal to each ton a little less than 2d. 



The shock of the blast was felt nearly all over Napier, much 

 more in some localities than in others, irrespective of distance. 

 Where it was most felt it resembled a sharp earthquake shock. 



The second mine was charged with two tons (4,000lbs.) of 

 Nobel's dynamite, and was fired on the 2nd April. The 

 chamber was 5 feet long, 3 feet 6 inches wide, and 5 feet high. 

 No timber or other lining was used, and the dynamite was 

 packed in its paper wrappers. Two trains of fuse were attached 

 to detonators, embedded in dynamite cartridges, and a few 

 detonators were placed in the adjacent cartridges. The fuses 

 were led away from the mine in timber casing to near the mouth 

 of the drive, which was tamped up in the manner described for 

 the powder blast. Dynamite being a very safe explosive to 

 handle, the precautions taken for the powder blast were not 

 enforced, and the workmen were able to go about in their boots 

 and to use naked lights, and no feeling of uneasiness prevailed 

 as when charging the powder mine. The length of the fuses 

 were 72 feet each ; and the mine fired in a little over half an 

 hour after they were lighted. 



In both cases the explosive chambers were situated 85 feet 

 from the face of the cliff". 



The effect of this latter blast was wonderful — its action 

 extended far away behind the blast : the hill opened obliquely 

 from the blasting point ; the face of the cliff rose, spread out 

 like a fan opening, and without any hesitation came down with 

 a thundering crash, followed by a low rumbling and a great 

 cloud of dust. There was but a small report, and very little 

 overhanging material left. Immediately above where the charge 

 bad been fired a regular funnel had been scooped up to the top, 

 by the pent-up vapours seeking an outlet. 



