Chain Home Low
Chain Home Low was the name of a British early warning radar system operated by the RAF during World War II. The name refers to CHL's ability to detect aircraft flying at altitudes below the capabilities of the original Chain Home radars, where most CHL radars were co-located. CHL could reliably detect aircraft flying as low as 500 feet; the official name was AMES Type 2, referring to the Air Ministry Experimental Station at Bawdsey Manor where it was developed, but this name was never used in practice. CHL traces its origins to early experiments with Airborne Interception radar systems in 1936; these were developed as a short-range radar that would be used to close the gap between Chain Home's approximate 5 miles accuracy and the visual range of a night fighter pilot at about 1,000 yards. Developed by a second team at Bawdsey Manor led by "Taffy" Bowen, the new radar had to operate at much smaller wavelengths in order to limit the antenna sizes to something that could be fit on an aeroplane.
After considerable experimentation, the team settled on a set working at 1.5 meter wavelength, about 193 MHz in the VHF band. In early experiments with the new set, the team found that detection of other aircraft was problematic due to their target's small size, but the strong returns from the ground; the latter caused a strong signal that appeared to be at a range equal to the aircraft's current altitude, everything beyond, invisible in the clutter. This meant that a typical night bombing run by German aircraft at 15,000 feet altitude would only become visible at that range, far less than the desired minimum of 5 miles; these same experiments demonstrated an unexpected side-effect. As the aircraft flew around over Bawdsey, located on the coast of the English Channel, the team found strong constant returns that they realized were the cranes at the Harwich Docks, miles away. Other smaller returns were identified as boats in the Channel; these were being detected at ranges far beyond the maximum range against aircraft, in spite of the antennas not being designed for this role.
The potential of this discovery was not lost, Robert Watson-Watt asked the team to demonstrate the concept in a real-world setting. A series of military exercises in the Channel in September 1937 provided a perfect test. On 3 September the team's test aircraft, Avro Anson K6260, detected several Royal Navy ships in the Channel, the next day repeated this performance in spite of complete overcast. Albert Percival Rowe of the Tizard Committee commented that "This, had they known, was the writing on the wall for the German Submarine Service." The British Army was the first to consider radar, when W. A. S. Butement and P. E. Pollard submitted a paper in 1931 suggesting using pulses of radio signal to measure the distance to ships; the Army was uninterested until they heard about Watt's work at Bawdsey, when they became interested. In October 1936 a liaison team led by E. T. Paris and Albert Beaumont Wood was set up at Bawdsey known as the Military Applications Section, but universally referred to as the "Army Cell".
The only two technicians with the required experience available were Butement and Pollard. The two began development of two projects, the Mobile Radar Unit, a mobile version of Chain Home, Gun Laying radar, a much smaller unit designed to provide range measurements against aircraft as an aid to aiming their anti-aircraft artillery; the teams had made considerable progress on both projects by the summer of 1937, with Gun Laying radar, Mk. I about to enter initial production, the MRUs taken over in 1938 by the RAF AMES Type 9. With this work starting to move from development to production, coincident with Bowen's astonishing anti-shipping demonstration, Butement began adapting Bowen's 1.5 m set for what became the Coast Defence radar, allowing the Army's coastal artillery to aim their guns at night or in fog. The CD set was in most respects a version of the GL working at the shorter 1.5 m wavelength, like GL, used separate transmit and receive antennas that had to be rotated together to be aimed at a target.
The earlier GL system operated at just over 6 m, which meant the antenna was large. The GL array had only four horizontal elements in it, which offered resolution on the order of 20 degrees; this allowed the operator to pick out a single aircraft as long as they weren't in formation, but could not be used to directly guide the guns. In contrast, the 1.5 m wavelength of the new sets allowed an antenna of about the same size to feature eight dipoles, reducing the angle to about 1.5 degrees. Although this was of marginal capability in terms of directly aiming the guns, in July 1939 it was noticed that when the Army's 9.2-inch guns missed their targets, the splash of water caused by the shell would cause a brief but obvious return on the radar sets. This meant that any inaccuracy in the radar antenna's measurements could be eliminated by comparing the target and the splashes on the screen, as these would both have the same error; the gunners could correct their fire onto the targets in the same fashion that they would when being given corrections by remote observers.
During early tests against Chain Home in 1938, RAF pilots had noticed they could escape detection by flying at low altitudes. This was due to the minimum angle of the CH being about 1.5 degrees above the horizon, which meant aircraft were below the radar's sight until they approached within a few miles. They could escape detection by flying between two CH stations at altitudes around 1,500 feet. At first this was not considered to be a serious limit
A burgh was an autonomous municipal corporation in Scotland and Northern England a town, or toun in Scots. This type of administrative division existed from the 12th century, when King David I created the first royal burghs. Burgh status was broadly analogous to borough status, found in the rest of the United Kingdom. Following local government reorganization in 1975 the title of "royal burgh" remains in use in many towns, but now has little more than ceremonial value; the first burgh was Berwick. By 1130, David I had established other burghs including Edinburgh, Dunfermline, Perth, Jedburgh and Lanark. Most of the burghs granted charters in his reign already existed as settlements. Charters were copied verbatim from those used in England, early burgesses invited English and Flemish settlers, they were able to impose fines on traders within a region outside their settlements. Most of the early burghs were on the east coast, among them were the largest and wealthiest, including Aberdeen, Berwick and Edinburgh, whose growth was facilitated by trade with other North Sea ports on the continent, in particular in the Low Countries, as well as ports on the Baltic Sea.
In the south-west, Glasgow and Kirkcudbright were aided by the less profitable sea trade with Ireland and to a lesser extent France and Spain. Burghs were settlements under the protection of a castle and had a market place, with a widened high street or junction, marked by a mercat cross, beside houses for the burgesses and other inhabitants; the founding of 16 royal burghs can be traced to the reign of David I and there is evidence of 55 burghs by 1296. In addition to the major royal burghs, the late Middle Ages saw the proliferation of baronial and ecclesiastical burghs, with 51 created between 1450 and 1516. Most of these were much smaller than their royal counterparts. Excluded from foreign trade, they acted as local markets and centres of craftsmanship. Burghs were centres of basic crafts, including the manufacture of shoes, dishes, joinery and ale, which would be sold to "indwellers" and "outdwellers" on market days. In general, burghs carried out far more local trading with their hinterlands, on which they relied for food and raw materials, than trading nationally or abroad.
Burghs had rights to representation in the Parliament of Scotland. Under the Acts of Union of 1707 many became parliamentary burghs, represented in the Parliament of Great Britain. Under the Reform Acts of 1832, 32 years after the merger of the Parliament of Great Britain into the Parliament of the United Kingdom, the boundaries of burghs for parliamentary elections ceased to be their boundaries for other purposes. There were several types of burgh, including. Burgh of regality, granted to a nobleman or "lord of regality". Burgh of barony, granted to a tenant-in-chief, with narrower powers. Parliamentary burgh or Burgh constituency, a type of parliamentary constituency. Police burgh; until 1833, each burgh had a different constitution or "sett". The government of the burgh was in the hands of a self-nominating corporation, few local government functions were performed: these were left to ad hoc bodies. Two pieces of reforming legislation were enacted in 1834: The Royal Burghs Act and the Burghs and Police Act.
The Royal Burghs Act provided for the election of councillors. Each burgh was to have a common council consisting of a provost and councillors; every parliamentary elector living within the "royalty" or area of the royal burgh, or within seven statute miles of its boundary, was entitled to vote in burgh elections. One third of the common council was elected each year; the councillors selected a number of their members to be bailies, who acted as a magistrates bench for the burgh and dealt with such issues as licensing. The provost, or chief magistrate, was elected from among the council every three years; the Royal Burghs Act was extended to the 12 parliamentary burghs, enfranchised. These were growing industrial centres, apart from the lack of a charter, they had identical powers and privileges to the royal burghs. Royal Burghs retained the right to corporate property or "common good"; this property was used for the advantage of the inhabitants of the burgh, funding such facilities as public parks and civic events.
The Burghs and Police Act allowed the inhabitants of Royal Burghs, Burghs of Regality and of Barony to adopt a "police system". "Police" in this sense did not refer to law enforcement, but to various local government activities summarised in the Act as "paving, cleansing, supplying with water, improving such Burghs as may be necessary and expedient". The Act could be adopted following its approval in a poll of householders in the burgh. Burghs reformed or created under this and legislation became known as police burghs; the governing body of a police burgh were the police commissioners. The commissioners were elected by the existing town council of the burgh, not by the electorate at large; the town council of a burgh could by a three-quarters majority become police commissioners for the burgh. In many cases this led to the existence of two parallel burgh administrations, the town council and the police commissioners, each with the same membership, but separate legal identity and powers. Further legislation in 1850 allowed "populous places" other than existing burghs to become police burghs.
In 1893, most of the anomalies in th
A single-track road or one-lane road is a road that permits two-way travel but is not wide enough in most places to allow vehicles to pass one another. This kind of road is common in rural areas across elsewhere. To accommodate two-way traffic, many single-track roads those designated as such, are provided with passing places or pullouts or turnouts, or wide spots in the road, which may be scarcely longer than a typical automobile using the road; the distance between passing places varies depending on the terrain and the volume of traffic on the road. The railway analog for passing places are passing loops; the term is used in Scotland the Highlands, to describe such roads. Passing places are marked with a diamond-shaped white sign with the words "passing place" on it. New signs tend to be square rather than diamond-shaped, as diamond signs are used for instructions to tram drivers in cities. On some roads in Argyll and Bute, passing places are marked with black-and-white-striped posts. Signs remind drivers of slower vehicles to pull over into a passing place to let following vehicles pass, most drivers oblige.
The same system is found occasionally in rural England and Wales, as well as Sai Kung in the New Territories. Sometimes two small vehicles can pass one another at a place other than a designated passing place; some A-class and B-class roads in the Highlands are still single-track, although many sections have been widened for the sake of faster travel. In 2009, the A830 "Road to the Isles" and A851 on Skye have had their single-track sections replaced with higher-quality single-carriageway road. In remote backcountry areas around the world in mountains, many roads are single-track and unmarked; these include many U. S. Forest Service and logging roads in the United States. In Peru, the second of two overland transportation routes between Cuzco and Madre de Dios Region, a 300 km heavy-truck route, is a single-track road of gravel and dirt; when practical, it is considered better for the vehicle going downhill to yield the right of way by stopping at a wide spot. The reason seems to be. At least in California, it is the vehicle going downhill that must back up, if it is too late to stop at a wide spot.
Chicanes are placed on residential streets as a more aesthetic means to slow-down cars. Sometimes, for budget reasons, where traffic is low, bridges exist as single-track corridors. Tunnels in remote areas can be one lane when the tunnel is short and traffic is low, when building a hill or blasting away the mountain is too cost prohibitive. Single-track roads exist as one-way stretches. Exit and entrance ramps for freeways and motorways are among common examples of one-way single-track roads; the most common example of private single-track roads are long driveways of rural properties such as country houses and farm property. The mountain passes on the Dalton Highway in Alaska have a rule where goods-carrying northbound truck traffic has the right of way, while returning southbound traffic has to stop, as mentioned on Ice Road Truckers; the reason behind this procedure is that traffic going north is in somewhat of a hurry to deliver equipment to Deadhorse, Prudhoe Bay, the drill site over the frozen Arctic Ocean.
When reconstruction is being done on 2-lane highways where traffic is moderately heavy, a worker will stand at each end of the construction zone, holding a sign with "SLOW" or "GO" written on one side and "STOP" on the reverse. The workers, who communicate through yelling, hand gestures, or radio, will periodically reverse their signs to allow time for traffic to flow in each direction. A modification of this for roadways that have heavier traffic volumes is to maintain one direction on the existing roadway, detour the other, thus not requiring the use of flaggers. An example of this is the M-89 reconstruction project in Plainwell, MI, where westbound traffic is detoured via county roads around town. If lines of sight are long, both drivers are familiar with the road, vehicles heading towards each other can adjust their speed so as to arrive at a wide spot at the same time and pass avoiding the need for either vehicle to stop; when two vehicles meet head-on the drivers confer to decide in which direction lies the closest wide spot, together they travel there, the lead vehicle in reverse gear.
In Scotland, where most drivers are accustomed to single-track roads, it is customary for drivers to acknowledge each other with a wave, or flash of headlights at night. In Scotland, if the passing place is to the right-hand side of a vehicle, the driver would never pull in to the passing place to let the other driver pass. Instead the driver would stop just short of the passing place on the road, to leave space for the oncoming vehicle to manoeuvre into the passing place which would be on their left. At night, if a driver were to see an oncoming vehicle in the distance and was reasonably close to a passing place, the driver would flash the headlights which would signal the other car to proceed forward while either the other vehicle reversed back to a passing place, or waited beside a passing place for the other car to arrive. In the United States, it is customary to move the right hand to the top of the steering wheel, palm down, raise four fingers; when there is a brief one-lane bottleneck of a 2-lane road, traffic will yield to oncoming traffic in the bottleneck.
One-lane single-track roads have no confl
The Pentland Firth is a strait which separates the Orkney Islands from Caithness in the north of Scotland. Despite the name, it is not a firth; the name is presumed to be a corruption of the Old Norse "Petlandsfjörð", meaning "the fjord of Pictland", is unrelated to the Pentland Hills near Edinburgh. Prior to the Norse occupation of Orkney the strait was known as the "Sea of Orcs" – a reference to the Pictish tribe who inhabited Orkney; such was their marine prowess that there are instances of this name referring to the sea lanes of the entire west coast of Scotland down to Kintyre. One version of the 9th-century Historia Brittonum states that "the Britons filled the whole island with their peoples from the English Channel to the Sea of Orcs". On the Caithness side the Firth extends from Dunnet Head in the west to Duncansby Head in the east, while on the Orkney side from Tor Ness on Hoy in the west to Old Head on South Ronaldsay in the east. In the middle of the Firth are two significant islands and Swona.
The small Pentland Skerries group are in the east. The islands of Hoy and South Ronaldsay border the firth to the north and are part of the Orkney Islands; the most northerly point of the headland of Dunnet Head, Easter Head, is that of mainland Britain. The famous John o' Groats and many smaller villages are to be found on the Caithness side as is the town of Thurso and Scrabster Harbour in Thurso Bay, on the western fringe of the Firth. In the West the ferry from Scrabster to Stromness operated by NorthLink is the oldest continuous ferry service across the firth by the ferry MV Hamnavoe, started in 1856 as a continuation of the railhead at Thurso; the Far North Line opened 28 July 1874 Historically the Gills Bay area has been the main setting off point from the mainland to the islands of Stroma and Swona and Orkney itself. At present Pentland Ferries operate on this route from Gills Bay to St Margaret's Hope on South Ronaldsay. At the eastern end John o' Groats Ferries sail to Burwick on South Ronaldsay.
This is run in the summer months only. Consideration was given to construction of a tunnel linking the islands to the mainland; the 10-mile tunnel was projected to have cost £100 million based on preliminary studies carried out in 2005 but as of 2012 no further progress has been made. The Firth is well known for the strength of its tides, which are among the fastest in the world, a speed of 30 kilometres per hour being reported close west of Pentland Skerries; the force of the tides gives rise to overfalls and tidal races which can occur at different stages of the tide. Some of the principal tidal races are: ‘The Merry Men of Mey’. Forms off St John’s point in the west-going stream and extends as the tide increases NNW across the firth to Tor Ness; the worst part is over a sand wave field about 5.5 kilometres west of Stroma. The waves formed by this race form a natural breakwater with calm water to the east of it noticeable when a westerly swell is running. Tides in this area can exceed 19 kilometres per hour.
‘The Swelkie’. The race at the north end of Stroma, off Swelkie Point is known as ‘The Swelkie’, it extends from the point in an easterly or westerly direction depending on the tide and can be violent. The whirlpool of the same name was, according to a Viking legend, caused by a sea-witch turning the mill wheels which ground the salt to keep the seas salty; the name derives from an Old Norse term, Svalga meaning "the Swallower". The ‘Duncansby Race’ forms off Ness of Duncansby at the start of the SE-going tidal stream. Extending ENE but wheeling anti-clockwise until it extends about 1.5 kilometres NW some 2½ hrs at which point it is known as ‘The Boars of Duncansby’. During the time of the SE stream there is additional turbulence off Duncansby Head to the East; the race temporarily ceases at the turn of the tide before forming in an ENE direction in the NW-going tidal stream before ceasing again at the next turn of the tide. The race is violent and dangerous when the tidal stream is opposed by gales in the opposite direction.
During the east-going stream a race forms off Ness of Huna. This race can be violent in an easterly or southeasterly gale; the ` Liddel Eddy' forms between Muckle Skerry in the East-going stream. A race forms for part of the time off Old Head at the SE part of South Ronaldsay. In addition to ` The Swelkie', races form at south ends of Stroma and Swona. Between the races there is a calm eddy; the races are visible with overfalls and whirlpools. Large swell waves can be present in bad weather conditions; when entering or leaving the eddies, crossing the races large powerful vessels can be pushed off course, such is the demarcation between the calm eddy and the fast-moving tide in the races. There are other races in the firth off Brough Head. Currents of up to 5 metres per second make the Pentland Firth one of the best sites in the world for tidal power; this has taken on a political dimension. The SNP Energy Review of July 2006 claimed that the Firth could produce "10 to 20 GW of synchronous electricity" and First Minister Alex Salmond claimed that the Pentland Firth could be "the Saudi Arabia of tidal power" with an output of "20 gigawatts and more than that".
In July 2013 Dr Thomas Adcock of Oxford University stated that the Firth "is certainly the best site for tidal stream power in the world" although a p
A map projection is a systematic transformation of the latitudes and longitudes of locations from the surface of a sphere or an ellipsoid into locations on a plane. Maps cannot be created without map projections. All map projections distort the surface in some fashion. Depending on the purpose of the map, some distortions are acceptable and others are not. There is no limit to the number of possible map projections. More the surfaces of planetary bodies can be mapped if they are too irregular to be modeled well with a sphere or ellipsoid. More projections are a subject of several pure mathematical fields, including differential geometry, projective geometry, manifolds. However, "map projection" refers to a cartographic projection. Maps can be more useful than globes in many situations: they are more compact and easier to store; these useful traits of maps motivate the development of map projections. However, Carl Friedrich Gauss's Theorema Egregium proved that a sphere's surface cannot be represented on a plane without distortion.
The same applies to other reference surfaces used as models for the Earth, such as oblate spheroids and geoids. Since any map projection is a representation of one of those surfaces on a plane, all map projections distort; every distinct map projection distorts in a distinct way. The study of map projections is the characterization of these distortions. Projection is not limited to perspective projections, such as those resulting from casting a shadow on a screen, or the rectilinear image produced by a pinhole camera on a flat film plate. Rather, any mathematical function transforming coordinates from the curved surface to the plane is a projection. Few projections in actual use are perspective. For simplicity, most of this article assumes. In reality, the Earth and other large celestial bodies are better modeled as oblate spheroids, whereas small objects such as asteroids have irregular shapes. Io is better modeled by triaxial prolated spheroid with small eccentricities. Haumea's shape is a Jacobi ellipsoid, with its major axis twice as long as its minor and with its middle axis one and half times as long as its minor.
These other surfaces can be mapped as well. Therefore, more a map projection is any method of "flattening" a continuous curved surface onto a plane. Many properties can be measured on the Earth's surface independent of its geography; some of these properties are: Area Shape Direction Bearing Distance ScaleMap projections can be constructed to preserve at least one of these properties, though only in a limited way for most. Each projection compromises, or approximates basic metric properties in different ways; the purpose of the map determines. Because many purposes exist for maps, a diversity of projections have been created to suit those purposes. Another consideration in the configuration of a projection is its compatibility with data sets to be used on the map. Data sets are geographic information. Different datums assign different coordinates to the same location, so in large scale maps, such as those from national mapping systems, it is important to match the datum to the projection; the slight differences in coordinate assignation between different datums is not a concern for world maps or other vast territories, where such differences get shrunk to imperceptibility.
The classical way of showing the distortion inherent in a projection is to use Tissot's indicatrix. For a given point, using the scale factor h along the meridian, the scale factor k along the parallel, the angle θ′ between them, Nicolas Tissot described how to construct an ellipse that characterizes the amount and orientation of the components of distortion. By spacing the ellipses along the meridians and parallels, the network of indicatrices shows how distortion varies across the map; the creation of a map projection involves two steps: Selection of a model for the shape of the Earth or planetary body. Because the Earth's actual shape is irregular, information is lost in this step. Transformation of geographic coordinates to Cartesian or polar plane coordinates. In large-scale maps, Cartesian coordinates have a simple relation to eastings and northings defined as a grid superimposed on the projection. In small-scale maps and northings are not meaningful, grids are not superimposed; some of the simplest map projections are literal projections, as obtained by placing a light source at some definite point relative to the globe and projecting its features onto a specified surface.
This is not the case for most projections, which are defined only in terms of mathematical formulae that have no direct geometric interpretation. However, picturing the light source-globe model can be helpful in understanding the basic concept of a map projection A surface that can be unfolded or unrolled into a plane or sheet without stretching, tearing or shrinking is called a developable surface; the cylinder and the plane are all developable surfaces. The sphere and ellipsoid do not have developable surfaces, so any projection of them onto a plane will have to dis
Royal Observer Corps
The Royal Observer Corps was a civil defence organisation intended for the visual detection, identification and reporting of aircraft over Great Britain. It operated in the United Kingdom between 29 October 1925 and 31 December 1995, when the Corps' civilian volunteers were stood down.. Composed of civilian spare-time volunteers, ROC personnel wore a Royal Air Force style uniform and latterly came under the administrative control of RAF Strike Command and the operational control of the Home Office. Civilian volunteers were trained and administered by a small cadre of professional full-time officers under the command of the Commandant Royal Observer Corps. In 1925, following a Defence Committee initiative undertaken the previous year, the formation of an RAF command concerning the Air Defence of Great Britain led to the provision of a Raid Reporting System, itself delegated to a sub-committee consisting of representatives from the Air Ministry, Home Office and the General Post Office; this Raid Reporting System was to provide for the visual detection, identification and reporting of aircraft over Great Britain, was to become known as the Observer Corps.
The Observer Corps was subsequently awarded the title Royal by His Majesty King George VI in April 1941, in recognition of service carried out by Observer Corps personnel during the Battle of Britain. Throughout the remainder of the Second World War, the ROC continued to complement and at times replace the Chain Home defensive radar system by undertaking an inland aircraft tracking and reporting function, while Chain Home provided a predominantly coastal, long-range tracking and reporting system. With the advent of the Cold War, the ROC continued in its primary role of aircraft recognition and reporting, in 1955 was allocated the additional task of detecting and reporting nuclear explosions and associated fall-out. By 1965, thanks to advances in technology, most roles and responsibilities relating to aircraft had been withdrawn and the ROC assumed the role of field force for the United Kingdom Warning and Monitoring Organisation. By the late 1980s the ROC comprised 69 professional full-time officers 10,500 civilian spare-time volunteers, over 100 Ministry of Defence civilian support staff.
At HQROC, over a dozen full-time secretarial and other administrative staff were present. Each of the five Area HQs were staffed by a clerical officer and a typist, each of the 25 Group HQs were staffed by a clerical officer and handyperson. Following the UK Government's Options for Change defence spending review in 1990, the vast majority of the civilian spare-time volunteers were stood down on 30 September 1991, with the remainder being stood down on 31 December 1995; the closure of HQROC on 31 March 1996 and redeployment of those few remaining HQROC staff marked the disbandment of the ROC after over 70 years of service. The ROC can trace its roots to the First World War and the requirement for a warning system to bolster UK defences, predominantly over south east England, against bombing raids by Zeppelin airships of the German Empire's Luftstreitkräfte. A system of observation posts and observers was organised, with a network of 200 posts established in strategic areas; these posts were manned by British Army personnel, who were in turn replaced by Special Constables, posts were coordinated on an area basis with telephone communications provided between themselves and their associated anti-aircraft defences.
Throughout 1917 Germany began to deploy increasing numbers of fixed-wing bombers, with the result that the number of airship raids decreased in favour of raids by such aircraft. In response to this new threat, Major General Edward Bailey Ashmore, a Royal Flying Corps pilot who commanded an artillery division in Belgium, was appointed to devise an improved system of detection and control; the system, called the Metropolitan Observation Service, encompassed the London Air Defence Area and extended eastwards towards the Kentish and Essex coasts. The Metropolitan Observation Service met with some success and although not operational until the late summer of 1918, the lessons learned were to prove invaluable for future developments in the field of aircraft observation and reporting. Major General E B Ashmore is considered to have been the founder of what would become the Royal Observer Corps. Following the Armistice in 1918, it had been intended that the knowledge and skills gained by the Metropolitan Observation Service during the First World War would be maintained for the future security of the nation.
However, by the end of 1920, the observation-post networks and their associated anti-aircraft hardware had been decommissioned, in 1922 the responsibility for air defence was transferred from the War Office to the Air Ministry. Following this transfer, Major General Ashmore, responsible for air defence during World War I, reported to a new Air Raid Precautions committee, established in January 1924. In areas surrounding Romney Marsh and the Weald a series of trials were undertaken to develop a Raid Reporting System which would employ an optimum arrangement of observation posts and associated control-centres. During 1925 these trials were further extended to cover parts of the counties of Essex and Hampshire, and
Ailsa Craig is an island of 99 hectares in the outer Firth of Clyde, 16 kilometres west of mainland Scotland, upon which blue hone granite has long been quarried to make curling stones. The now uninhabited island is formed from the volcanic plug of an extinct volcano; the island, colloquially known as "Paddy's milestone", was a haven for Catholics during the Scottish Reformation in the 16th century, but is today a bird sanctuary, providing a home for huge numbers of gannets and an increasing number of puffins. An early reference to the rock is made by Sir Donald Monro, Archdeacon of the Isles who referred to the rock as "Elsay" in the 16th century; the modern name of the island is an anglicisation of the Gaelic, Aillse Creag meaning "fairy rock". An alternative Gaelic name is Creag Ealasaid meaning "Elizabeth's rock"; the first element, Aillse may represent Allt Shasann, "cliff of the English", mentioned in the Book of Leinster as Aldasain. The island is sometimes known as "Paddy's Milestone", being the halfway point of the sea journey from Belfast to Glasgow, a traditional route of emigration for many Irish labourers going to Scotland to seek work.
As a result of being the most conspicuous landmark in the channel between Ireland and Scotland, the island is known by a number of different names. The Bass Rock is sometimes nicknamed "the Ailsa Craig of the East", although its prominence in the Firth of Forth is not as great as that of Ailsa Craig in the Firth of Clyde. A number of features and places on the island have acquired names, Gaelic in most cases, such as Craigna'an; some names seem self-explanatory and indeed the'Swine Cave' may refer to a time when the Earl of Cassilis received part of his rent in hogs from the island. The island is 16 km west of Girvan; the island is part of the administrative district of South Ayrshire, in the ancient parish of Dailly. Geologically, Ailsa Craig is the remains of a volcanic plug from an extinct volcano, it stands out because all younger sedimentary rocks covering Southwest Scotland have long since been eroded away. But the island survived erosion because it is composed of much harder igneous rocks from the Palaeogene period.
The plug, composed of granite, is all that remains from the massive volcanic activity caused by the formation of the Atlantic Ocean. Dykes of similar age can be found in Scotland through other older rocks such as the extensive Cleveland and Eskdalemuir dykes. Though only a few metres across, these volcanic dykes can be traced all the way from northern England back to an ancient supervolcano on the Isle of Mull. Research has shown that the granite on Ailsa Craig has an unusual crystalline composition that has a distinctive appearance but a uniform hardness; these properties have made the island's rock a favourite material for curling stones. The island has a fresh-water spring but no electricity, sewage or telephone connections. Apart from 2 hectares sold to the Northern Lighthouse Board in 1883, the island belongs to The 9th Marquess of Ailsa. In May 2011 it was announced. Reports in December 2013 claimed an unnamed environmental trust had placed a formal bid, while in April 2014 the National Trust of Scotland was reported to be considering a bid.
The chief well on the island lies above'the Loups' and this was used by the Northern Lighthouse Board who built a cistern there and piped the water to the lighthouse complex. The'Horse Well' was located behind the gasworks. Four cottages, a shed and a small area of adjacent land are in the ownership of the Scottish Indian business tycoon Bobby Sandhu, purchased for £85,000 from the Northern Lighthouse Board. A five-star hotel was to be built; the only surviving buildings on the island are the lighthouse on its east coast facing the Scottish mainland, a ruined towerhouse, built by Clan Hamilton to protect the area from Philip II of Spain in the 16th century and the old quarry manager's house, used by the RSPB. Mrs Margaret Girvan ran a tearoom in a wooden building that stood next to the tacksman's cottage, famed for its pristine white table cloths and fresh scones. Mrs Girvan kept goats in stone-built goat pens on the good grazing near Garry Loch; the feral billy goats were wont to interfere with these nanny goats and this was another reason for their demise.
Fishermen seem to have used the island for centuries, first being noted in 1549 and it is recorded that they at one time slept beneath sails stretched over hollows on the beach. A fishermen's cottages row was under construction in the 1840s. However, the main developer died, the project was abandoned, with the area used instead as a walled kitchen garden until the gasworks was built; the island seems to have been a part of the Barony of Knockgarron that lay in the Parish of Dailly and the holder, Duncan of Turnberry, Earl of Carrick established the abbey of Crossraguel and endowed it with the island of Ailsa Craig to "provide f