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Pat, Bernard has hit the nail on the head. The introduction of high explosives (not just dynamite but also tonite and lithofracteur) went hand in hand with the introduction of boring machines. Other points worth considering are the impact of Bickford's safety fuze (1831) and the development of more sophisticated multi hole blasting techniques during the1870's. If you are interested in the minutiae regarding the introduction of rock drills into Cornish mining between 1864 and 1882 (my pet subject) contact me off list. Rick Stewart ----- Original Message ----- From: "Pat Clune" <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, March 18, 2003 5:19 PM Subject: Re: Dynamite and mining production > Bernard > > Very interesting information. The significance of the powered drills can not > overstated. Thanks for your input - it will help. > > Pat > ----- Original Message ----- > From: "Bernard Moore" <[log in to unmask]> > To: <[log in to unmask]> > Sent: Monday, March 17, 2003 5:28 PM > Subject: Re: Dynamite and mining production > > > > Dear Pat, > > > > The true effectiveness of dynamite explosives was dependent to a large > part > > on how fast a hole could be drilled to put it in! Therefore the history of > > drilling machines plays a significant role in the matter. > > > > Granted dynamite expls. had a significant impact simply by their VOD over > > blasting powder, but ground conditions and the expertise in their use > again > > plays a large part. Most serious books on Cornish mining will give you a > good > > idea as to the increase in ground breaking, but the main feature - > always - > > was the introduction of compressed air drilling machines (particularly in > > driveage). > > > > I feel, as a ballpark figure, a 30% increase was achieved with hand > drilling, > > and 70% by machine with driveage (average figures). Stoping is another > matter > > of course, but the numbers will be roughly similar. > > > > I hope this might be of some use. Regards, Bernard > > > >