This article is copyrighted by and all rights reside with the author P.L. McCarthy
Although the method Agricola* described for breaking rock might be regarded as the most primitive imaginable, the origins of metal mining in fact go back much further. There is little doubt that bronze tools were being used for mining purposes 6,000 years ago, with the Egyptians removing hard rock by building a fire against the face, then throwing water on the heated rock - the sudden contraction causing the rock to crack.
This "fire-setting" method, first mentioned by Agatharchides in the second century BC, was reportedly used until the seventeenth century and the advent of gunpowder. The concept of drilling holes in rock for blasting purposes was first proposed by Martin Weigel, the mine superintendent at Freiberg, Germany, in 1613 with the first successful use of the said method attributed to Casper Windt, at Schemintz, four years later. But it was to be two centuries later before a practical, mechanised rock drill was demonstrated.
Drilling - using the "hammer and tap" method - and blasting were introduced to England in 1670, adopting either the "single jack" (one-man) or "double jack" methods for deeper holes. Even faster drilling became possible in 1749 when Hungarian miners introduced the chisel-bit drill in the Hartz mountains, but the use of black powder for blasting remained highly risky in the absence of a reliable fuse. Poor ventilation and dust added to the risk. Whereas 200 years had passed since Agricola had noted that "there were women in the Carpathian mountains who had married seven husbands, all of whom had died from consumption", blackpowder accidents in the 1700s more often mangled their victims than killed them outright.
Much of the danger of premature explosions, hangfires and misfires was overcome with the invention of the safety fuse by William Bickford, of Tuckingmill in the UK, in 1831. Electric detonators had been invented two years earlier - by Moses Shaw in New York - while nitroglycerine was discovered by Sobrero 16 years later, in 1847, all of which made blasting a far more effective (and less dangerous) procedure.
But a superior method of drilling than hammer and tap was necessary if mining was to become more efficient. The idea of fastening a detachable tool to a mechanically moved piston rod dates from the invention of the steam hammer in about 1842. Its drawback, however, was that the steam delivery lines had to be kept short and well insulated to prevent the steam from condensing before it reached the cylinder, effectively limiting steampowered rock drills to surface (and not underground) use.
It was in 1844 that Brunton, an Englishman, suggested using compressed air in a rock drill, naming it the "wind hammer". It was five years later when J W Fowle, in Boston, took out a patent for a modern rock drill with many additional features. Despite further enhancements of the Fowle drill - by Bartlett in 1855 who tested it in the first of the major tunnelling projects, the Mont Cenis tunnel - the steam-driven drills continued to be extremely unreliable until further modifications -by Sommeiller in the 1860s - saw a machine of the same name go into regular use, including use in underground mining at Moresuet, Belgium in 1863.
Fortunately, following worldwide publicity given to the drill used in the Mont Cenis project, there was a boom in research and development over the next decade with the Haupt drill and a number of others, including the development of the rifle-bar and ratchet-wheel piston assembly, being released and tested in mines and tunnels across the world.
Notwithstanding numerous claims, most of the drills referred to were crude and a source of troublesome dust. Because of the primitive metallurgy at the time, the metals used were inadequate and machining tolerances not sufficiently fine. The invention of dynamite in 1867, whilst making blasting safer, aggravated the dust problem by its shattering effect.
The use of compressed air aided ventilation in mines as it was breathable when exhausted by the drill and the expansion of the exhaust air helped cool the atmosphere.
* Georgius Agricola (1494-1555). German scholar and physician, known as the father of mineralogy. His work, the first to be based on practical knowledge and direct observation, initiated the development of modern geology and the study of metals. In his book De Re Metallica, published in 1555, he summarised all that was known of mining and smelting at that time. An unfortunate by-product of the same process saw the exhaust ports of the rock drill grow extremely cold, often freezing over. The water forming this ice came in through the compressed air delivery line with the air, having been added deliberately at the compressor! The early designs of air compressors all required water injection, with many having water-filled cylinders to remove the heat of compression. Meanwhile, attempts to build compressors for 'dry' air resulted in explosions when the cylinder lubricant vaporised and was ignited by the high temperature. The concept of the multi-stage air compressor with intercooling and water jacket had not yet arrived. Nevertheless, by the close of the 1860s, several promising rock drills - many of which were operating successfully in underground mines - and a reliable, powerful and safe explosive had been developed. At the same time, new goldfields were opening up in Australia, with mining companies ready to embrace this new technology.