List of words

D Words	Meaning
Dag	timberman’s axe with a 2ft handle used for trimming and chopping timber
Dam	Any structure or pond to contain or hold back water Dam Door – A reinforced steel door set in concrete that, in the event of an inrush of water, can be securely closed to prevent further flooding of mine workings. Slime Dam – One of a number of reservoirs or ponds wherein the fine material carried back by the gutters can settle out before the water is pumped to surface
Deck	Level suspended walkways and platforms within structures, i.e. crusher pits, pump stations. Cage Deck – Most of the mine cages in SC were split horizontally into two man carrying compartments, known as bottom and top deck. The bottom deck of the cages used in Robinson’s Shaft up to the late 60’s was just high enough to contain a ¾ ton wagon, and when used for manriding six people would crouch in it uncomfortably, it was generally referred to as the pigpen
Decline	Term used for tunnels driven downhill at various angles to provide access, transport and service ways deeper into the mine. SC had two sub decline shafts dipping at 1 in 4 (25%) grade giving access via track and conveyors from 380 to 445 fathom levels. The Tuckingmill Decline, before financial constraints intervened, was driven over half a kilometre from surface dipping at 1in 6, then 1in 5, and was intended to provide vehicular access into, and out of, the mine
Derail	The process whereby equipment running on railway track comes of the rails. Incline Derailer – A device mounted at the lower end of wagons in the declines during sinking operations. It comprised a strong steel rod dragged along when the loaded wagons were going up-hill and was intended to dig in, lift and skew the wagon so that it derailed if it started to run back down for any reason.
Det	General term for any detonator i.e. Det Box
Detaching Gear	Devices placed between the winding rope and the cage or skip shackle points. They come into play if the cage or skip is overwound and pulled too high in the headgear. A shear bolt is triggered allowing catches to spring out and at the same time release the shackle on the rope. The cage or skip is then left suspended by the catches, the winding rope generally going over the sheave wheel to the ground.
Detonating Cord	Cords of various thicknesses and strengths comprising a tough, waterproof braiding inside which is a core of PETN, a very powerful explosive with a high VOD. It is used to trigger explosives in holes, to ensure long lengths of explosives detonate in one go, to crack ground between holes in smooth blasting and, in low power cords to initiate non-electric detonation systems.
Detonator	A device containing small quantities of sensitive high explosives which is used to initiate more stable explosives. Detonator Box – A container made of non ferrous materials (wood or plastic with brass fittings inside) used to transport detonators from the surface store to the workplace and to hold the securely until required Delay Detonators – Many types of detonators have delays built into them so that though they are all initiated together they go off in a required sequence. This enables rock to be broken away to create free faces before more is blasted. Delays commonly used are half or tenth of second for development rounds, and millisecond for long hole blasting. Electric Detonators – The most common detonators used from the 60’s to the 80’s, using a high voltage electrical charge to initiate them. They came in either instantaneous or delay type and had a copper or aluminium casing with colour coded wires for connecting up with. Fuse Detonators – Detonators crimped to safety fuse were used up to the 60’s for most shotfiring purposes and in rounds and benches were timed by the shotfirer cutting the fuse to set lengths, and/or lighting the fuse in strict order and time. Secondary blasting with fuses carried on until the 80’s, it being relatively simple to carry out. Millisecond Detonators – These are used particularly in blasting long hole stope rings, the holes being initiated at 25 millisecond intervals and because of the rapid firing, tend to sublimate the resultant shock waves through the surrounding rock to surface, and to increase fragmentation. Shock Tube Detonators – These are delay type detonators which are initiated by thin plastic tubes coated on the inside with PETN. The tubes are clipped to low power Detonating cord onto which is attached an electric, or other, detonator. The millisecond system uses a half second shock delay at the attachment point in order for all the detonator tubes to be initiated before the first holes go off. These detonators are also referred to as Non-electric detonators
Diamond	The hardest substance commercially available Diamond Bit – A thin walled, hollow cylindrical bit with pieces of industrial diamond set around the ‘top’ of the cylinder used for obtaining cores for geological purposes. Diamond Drill – A machine that turns and pushes a string of hollow drill steels with a diamond bit on the front. Depending on size and power these drills can obtain core samples many hundreds, or thousands, of metres long. The drill steel sections are withdrawn at set intervals, the length of the core section, and the core removed for further analysis.
Diesel	Loco
Dieseling	Ignition of lubricating oil in rock drill cylinder whilst in operation
Dip	Term used to denote the angle at which the lode is to the horizontal
Dipper	A lode that intersects or runs contrary to the general trend of lodes
dirt	the product of a blast (broken rock)
Dirt Over-run	Result of broken rockt flowing out of a chute or pass out of control and piling up around the wagon or crusher beneath it.
Divider	A timber or steel section that is set between the compartments of a shaft, and to which the runners are generally fastened.
Dog	A common term for a track spike, used to hold narrow gauge flat bottomed rails to wooden sleepers. Dogs come in various sizes according to the track weight and usage, are square in cross section and have a large, angled head. Dog Down – The action of hammering dogs into the sleepers to hold track in place. Dog Spike – Another name for a dog Track Dog – As above
Dolly Wheel	A single pulley wheel or roller used to guide or re-align a rope passing over it.
dowel	see L Peg
Draw point	At South Crofty these were the short crosscuts that joined the side-tye to the bottom of a working stope at right angles (if possible), and in which an air shovel was used to load broken rock from the stope pile and dump it into wagons in the side-tye. Drawpoint loading was introduced to South Crofty in the late 1970’s and soon superceeded loading from chutes as it was more efficient and more or all of the lode could be extracted. It did however entail the mining of the side-tyes and drawpoints in waste rock.
Drifter	These are heavy duty rock drills mounted in a cradle which has a chain or screw feed to push the machine forward and therefore keep the drill bit against the ground it is drilling. The cradle itself was, up to the 50’s mounted on a bar and arm, later they were attached to hydraulic booms to align and hold them.
Drill	A term covering many differing meanings, a drill could mean the rock drill machine, the drill steel, the action of drilling holes in rock. Below are more specific meanings. Drill Bit – The tip of the rock drill steel, whether integral or detachable, where the actual breaking and crushing of the rock takes place. Drill and Blast – The term used for the task of the machineman/shotfirer and mate, which is to drill the shot holes, charge them with explosives and fire the round. Drill Ladder – A short, wide, steel ladder with prongs that was either :- a) placed on the ground and either hooked to a transverse bar or the prongs dug into the ground. The air leg foot was hooked into the rungs and prevented the leg slipping back when drilling low holes, or b) Placed on the staging of a raise and used to hold the foot of the air leg. Drill Pattern – The layout of the shotholes on the face which enabled optimum breaking of the round of holes. Drill Steel – High quality flexible steel, generally round or hexagonal in cross section that comes in a variety of lengths and types for the variety of bits and drilling machines. Drill Water – The water supplied through pipes to the working places at sufficient pressure to flush the holes as they are being drilled.
Drilling	General term used for the action of using a rock drill to create holes in rock for shotfiring, support or other purposes. Dry Drilling – A bad practice outlawed in many mines whereby mechanical drilling of rocks takes place without water flushing the particles of broken rock from the drill bit, thus forming clouds of dust in the atmosphere. This fine dust in silica bearing rock was the primary cause of Pthysis, a deadly disease of the lungs.
Drive	A horizontal tunnel of required dimension following the trend of the lode, and which may be used to exploit the ore body if suitable Footwall Drive – These drives are driven in the country rock, i.e. granite, killas, alongside the lode drive, and provide access where the ore body in the lode is to be totally removed. Lode Drive – The drive following the lode faithfully, generally driven on the footwall of the lode. Lode drives in Cornish mines tend to weave and turn due to the vagaries of the lodes.
Dropper	A branch of a lode falling away from the footwall of a lode
Drop Set	Generally a half length set of track made by welding two rails to three or more narrow steel plates. Dropsets are used as temporary extensions of track in working headings and are usually used in combination with slider sets.
Drum	A cylinder on which wire rope is wound. Scraper Drum – The drum, of either two or three on which the wire rope used to move a scraper hoe are wound and unwound. Winder Drum – The drum on which the wire rope attached to a cage or skip in a mineshaft is wound and unwound
Drummy	Term used to denote loose rock in a mine. When struck with a steel bar (pinch bar or drill steel) drummy ground gives a hollow sound, whereas sound ground gives a satisfying ring.
Dry	The building on surface where the miner changes into and out of his work clothes, and at the end of shift has a shower, or bath, wash, whatever. Generally each miner has two lockers, one for clean clothes, the other for his work clothes. This locker nowadays has hot air passing through it to dry the clothes when the miner is ‘off-shift’.
Duckbill	Term for any device with the entry end is wider than the other, and generally with low sides. Duckbill Ramp – Structure in front of a scraper system whereby the scraper hoe is directed to the required discharge point. Duckbill Rerailer – Device put across a rail and into which a derailed vehicles wheels are dragged and pulled up, over and back onto track.
Dump	Place where loaded wagons, etc. are tipped into a pass. Dump Bars – Lengths of pipe or timber preventing personnel from falling into a grizzley or open pass at a dump point. They are slid or lifted away when wagons are to be tipped. Dump Chain – Lengths of heavy duty chain fastened between the back and floor at a dumping point to prevent wagons falling into the dump when being tipped. Ore Dump – Place where rock containing ore is tipped. Waste Dump – Place where waste rock is tipped.
Dust	Fine particles of crushed rock that ‘float’ in the air whenever disturbed, causing respiratory problems, and a visibility hazard
Dyke	A band of rock injected, when molten, into cracks in the surrounding rock, generally refers to rock not being mined. Elvan Dyke – See Elvan.
Dynamite	Name of the first explosives invented by Alfred Nobel, but used as a general term for all or any nitroglycerine based explosive. Dynamite Head – Referred to normally as ‘Dyni-head’, a thumping headache associated with handling nitroglycerine based explosives. It acts as a vasodilator, opening up blood vessels in the head, and elsewhere.

Peter Hughes has supplied words of this colour
D.C.Williams at Exeter University, better known as Gus. has supplied words of this colour
The remainder are supplied by Michael Davis

List of words “used” in the Cornish tin mines