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Re the school class visit to a "gravel pit" and the comment about drilling without water "because the rock was limestone". Most of Gibraltar is made of limestone and, certainly when I was there in 1953 in Tunnelling Troop, Royal Engineers, all drilling was done dry -- including that in a three hundred foot long eight foot by eight foot heading. The full round of 20 to 24 holes was put in using a Holman Silver Three drill, hand-held ( we had one air-leg, but it was broken ). The "master driller", a lad from Derbyshire, formerly a fluorspar mine worker, used to emerge at the end of the shift looking like a snowman. The story was that, being limestone, the dust was no problem. Certainly, it didn't seem to bother him -- it was what he had done at home in Derbyshire, anyway! What puzzles me is that dry drilling in limestone, and the use of a cone crusher, should be taking place in what is called a "gravel pit". Was this not a limestone quarry, where the rock was crushed and screened to produce aggregate? I would associate the term "gravel pit" with the working of a naturally occurring alluvial sand and gravel deposit where there was no rock to drill or crush. Tony Brewis %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%