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The holes you find, may be the back end of longer holes that were drilled but where the back did not pull too well. This still happens where you may end up re-drilling up to as much as a third of the rock if you have a poor drilling design. Our students still do hand steeling as part of the International student Mining competitions but they only drill to multiples of 6- inch deep holes. It may also be a function of what you are drilling into. Dave On Nov 10, 2006, at 9:21 AM, david hardwick wrote: > ... With hand drilling the miner would not be drilling a round as > we know it > today so in most circumstances there would be no reason to go for long > holes. > - Tony Brooks > > > Currently exploring/surveying a drainage adit - original adit was > late 1600s > but a new pumping engine was erected in 1790 and it is suggested > ours may be > a later (or at least altered) adit. > > Most of the length is stone arched but section through rock has > drill holes. > The diameter is inch and a half and the longest found is about 12 > inches. > > Would be interested in comments > > Regards > David >