100 ANNUAL OF SCIENTIFIC DISCO VERr. 



the match burns down to the powder and fh-es it. Then ensues 

 a violent shock, which immediately causes the detonation of the 

 nitroglycerine. The explosion is so sudden that the sand is not 

 even projected. 



The wliole mass of the rock rises, is displaced, then re-settles 

 without any projection ; only a dull detonation is heard. 



Only on examining the sjjot can an idea bo formed of the power 

 of the force developed by the exj)lo.siun. Formidable masses of 

 rock are slightly disijlaced and rent in every direction, and ready 

 to be removed mechanically. 



The chief advantage is that the stone is onl}' slightly crushed, 

 and there is very liltle waste. 



In the manner we have shown, from forty to eighty cubic 

 metres of rock may be detached by charges of nitroglycerine. 



We trust to have shown by this notice the possil)ility of recon- 

 ciling the employment of nitroglycerine with every desirable 

 guarantee for public safety. — M. Koi'i', Comptes Rendus. 



The following are extracts from a letter by T. P. Shaffner, in 

 the "Scientific American," for Nov., 18G6 : — 



"When I visited the Iloosac Tunnel in August, I had not wit- 

 nessed the explosion of nitroglyewine in rock of the hardness of 

 the Hoosac Mountain. The tunnel is jjenetrating through solid 

 massed mica and quartz. The strata lie against the progress, 

 and there are but few seams and slips. It tears roughly, and in 

 no instance (piarries. Every culjic inch nuist be blasted. 



" The ' heading' is G feet high and 15 feet wide. Below is the 

 ' bench,' or bottom enlargement, 4i feet deep, the width of the 

 heading. In the west shaft it was about 300 feet in the rear of 

 the heading. The further enlargements are to be above and at 

 the sides. My experiments wei-e in the west shaft, ' bench ' and 

 * heading,' proceeding eastward. 



" Prior to my arrival, good minei-s had been making from 2 to 

 3 feet per day with tlie ' bench.' The holes had been set from 15 

 to 20 inches back, drilling 4 holes to make the width of the 

 tunnel. These 4 holes were drilled 4 feet deep, charged with 

 powder and well tamped. After blasting the 4 holes, about 5 

 short holes, averaging 15 inches, had to be drilled in order to 

 make an even bottom. According to these figures, the number 

 of inclies to be drilled to make 60 7-10 feet lineal, would be 9,612, 

 Two men can drill about 100 inches per day of 8 hours, and 

 wages are §2.25 per day. The expense for miners, tools, and 

 incidentals, amounts to about $6 per 8 hours, for each 100 inches, 

 making a total of $566.72 for drilling. The time required to make 

 60 7-10 feet would be at least 20 days. There would be about 144 

 long holes, 180 short holes, and at least 36 blasts. This is the 

 I'ate of j3rogres3 that had 1>eeu made with gunpowder. 



"My lirst experiment was in the 'bench,' as above described, 

 and within 3 days I advanced 60 7-10 feet. I used nitroglycerine, 

 exploded by the aid of electricity. If the rock could be removed 

 after each blast, I can make 70 feet in that time. I had 9 blasts 

 and 28 holes, 5 feet deep ; total inches drilled, 1,G80. The cost 

 of the nitroglycerine Avas less than the j)rice of gunpowder for the 

 same number of feet. 



