penzance

ime angl. mesta

сущ.; геогр.

SUBJECT AREA: Chemical technology, Mining and extraction technology

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Educated at the Latin School at Penzance and from 1792 at Truro Grammar School, Davy was apprenticed to a surgeon in Penzance. In 1797 he began to teach himself chemistry by reading, among other works, Lavoisier's elementary treatise on chemistry. In 1798 Dr Thomas Beddoes of Bristol engaged him as assistant in setting up his Pneumatic Institution to pioneer the medical application of the newly discovered gases, especially oxygen.

In 1799 he discovered the anaesthetic properties of nitrous oxide, discovered not long before by the chemist Joseph Priestley. He also noted its intoxicating qualities, on account of which it was dubbed "laughing-gas". Two years later Count Rumford, founder of the Royal Institution in 1800, appointed Davy Assistant Lecturer, and the following year Professor. His lecturing ability soon began to attract large audiences, making science both popular and fashionable.

Davy was stimulated by Volta's invention of the voltaic pile, or electric battery, to construct one for himself in 1800. That enabled him to embark on the researches into electrochemistry by which is chiefly known. In 1807 he tried decomposing caustic soda and caustic potash, hitherto regarded as elements, by electrolysis and obtained the metals sodium and potassium. He went on to discover the metals barium, strontium, calcium and magnesium by the same means. Next, he turned his attention to chlorine, which was then regarded as an oxide in accordance with Lavoisier's theory that oxygen was the essential component of acids; Davy failed to decompose it, however, even with the aid of electricity and concluded that it was an element, thus disproving Lavoisier's view of the nature of acids. In 1812 Davy published his Elements of Chemical Philosophy, in which he presented his chemical ideas without, however, committing himself to the atomic theory, recently advanced by John Dalton.

In 1813 Davy engaged Faraday as Assistant, perhaps his greatest service to science. In April 1815 Davy was asked to assist in the development of a miner's lamp which could be safely used in a firedamp (methane) laden atmosphere. The "Davy lamp", which emerged in January 1816, had its flame completely surrounded by a fine wire mesh; George Stephenson's lamp, based on a similar principle, had been introduced into the Northumberland pits several months earlier, and a bitter controversy as to priority of invention ensued, but it was Davy who was awarded the prize for inventing a successful safety lamp.

In 1824 Davy was the first to suggest the possibility of conferring cathodic protection to the copper bottoms of naval vessels by the use of sacrificial electrodes. Zinc and iron were found to be equally effective in inhibiting corrosion, although the scheme was later abandoned when it was found that ships protected in this way were rapidly fouled by weeds and barnacles.

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SUBJECT AREA: Civil engineering, Land transport, Mechanical, pneumatic and hydraulic engineering, Ports and shipping, Public utilities, Railways and locomotives

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The son of Marc Isambard Brunel and Sophia Kingdom, he was educated at a private boarding-school in Hove. At the age of 14 he went to the College of Caen and then to the Lycée Henri-Quatre in Paris, after which he was apprenticed to Louis Breguet. In 1822 he returned from France and started working in his father's office, while spending much of his time at the works of Maudslay, Sons \& Field.

From 1825 to 1828 he worked under his father on the construction of the latter's Thames Tunnel, occupying the position of Engineer-in-Charge, exhibiting great courage and presence of mind in the emergencies which occurred not infrequently. These culminated in January 1828 in the flooding of the tunnel and work was suspended for seven years. For the next five years the young engineer made abortive attempts to find a suitable outlet for his talents, but to little avail. Eventually, in 1831, his design for a suspension bridge over the River Avon at Clifton Gorge was accepted and he was appointed Engineer. (The bridge was eventually finished five years after Brunel's death, as a memorial to him, the delay being due to inadequate financing.) He next planned and supervised improvements to the Bristol docks. In March 1833 he was appointed Engineer of the Bristol Railway, later called the Great Western Railway. He immediately started to survey the route between London and Bristol that was completed by late August that year. On 5 July 1836 he married Mary Horsley and settled into 18 Duke Street, Westminster, London, where he also had his office. Work on the Bristol Railway started in 1836. The foundation stone of the Clifton Suspension Bridge was laid the same year. Whereas George Stephenson had based his standard railway gauge as 4 ft 8½ in (1.44 m), that or a similar gauge being usual for colliery wagonways in the Newcastle area, Brunel adopted the broader gauge of 7 ft (2.13 m). The first stretch of the line, from Paddington to Maidenhead, was opened to traffic on 4 June 1838, and the whole line from London to Bristol was opened in June 1841. The continuation of the line through to Exeter was completed and opened on 1 May 1844. The normal time for the 194-mile (312 km) run from Paddington to Exeter was 5 hours, at an average speed of 38.8 mph (62.4 km/h) including stops. The Great Western line included the Box Tunnel, the longest tunnel to that date at nearly two miles (3.2 km).

Brunel was the engineer of most of the railways in the West Country, in South Wales and much of Southern Ireland. As railway networks developed, the frequent break of gauge became more of a problem and on 9 July 1845 a Royal Commission was appointed to look into it. In spite of comparative tests, run between Paddington-Didcot and Darlington-York, which showed in favour of Brunel's arrangement, the enquiry ruled in favour of the narrow gauge, 274 miles (441 km) of the former having been built against 1,901 miles (3,059 km) of the latter to that date. The Gauge Act of 1846 forbade the building of any further railways in Britain to any gauge other than 4 ft 8 1/2 in (1.44 m).

The existence of long and severe gradients on the South Devon Railway led to Brunel's adoption of the atmospheric railway developed by Samuel Clegg and later by the Samuda brothers. In this a pipe of 9 in. (23 cm) or more in diameter was laid between the rails, along the top of which ran a continuous hinged flap of leather backed with iron. At intervals of about 3 miles (4.8 km) were pumping stations to exhaust the pipe. Much trouble was experienced with the flap valve and its lubrication—freezing of the leather in winter, the lubricant being sucked into the pipe or eaten by rats at other times—and the experiment was abandoned at considerable cost.

Brunel is to be remembered for his two great West Country tubular bridges, the Chepstow and the Tamar Bridge at Saltash, with the latter opened in May 1859, having two main spans of 465 ft (142 m) and a central pier extending 80 ft (24 m) below high water mark and allowing 100 ft (30 m) of headroom above the same. His timber viaducts throughout Devon and Cornwall became a feature of the landscape. The line was extended ultimately to Penzance.

As early as 1835 Brunel had the idea of extending the line westwards across the Atlantic from Bristol to New York by means of a steamship. In 1836 building commenced and the hull left Bristol in July 1837 for fitting out at Wapping. On 31 March 1838 the ship left again for Bristol but the boiler lagging caught fire and Brunel was injured in the subsequent confusion. On 8 April the ship set sail for New York (under steam), its rival, the 703-ton Sirius, having left four days earlier. The 1,340-ton Great Western arrived only a few hours after the Sirius. The hull was of wood, and was copper-sheathed. In 1838 Brunel planned a larger ship, some 3,000 tons, the Great Britain, which was to have an iron hull.

The Great Britain was screwdriven and was launched on 19 July 1843,289 ft (88 m) long by 51 ft (15.5 m) at its widest. The ship's first voyage, from Liverpool to New York, began on 26 August 1845. In 1846 it ran aground in Dundrum Bay, County Down, and was later sold for use on the Australian run, on which it sailed no fewer than thirty-two times in twenty-three years, also serving as a troop-ship in the Crimean War. During this war, Brunel designed a 1,000-bed hospital which was shipped out to Renkioi ready for assembly and complete with shower-baths and vapour-baths with printed instructions on how to use them, beds and bedding and water closets with a supply of toilet paper! Brunel's last, largest and most extravagantly conceived ship was the Great Leviathan, eventually named The Great Eastern, which had a double-skinned iron hull, together with both paddles and screw propeller. Brunel designed the ship to carry sufficient coal for the round trip to Australia without refuelling, thus saving the need for and the cost of bunkering, as there were then few bunkering ports throughout the world. The ship's construction was started by John Scott Russell in his yard at Millwall on the Thames, but the building was completed by Brunel due to Russell's bankruptcy in 1856. The hull of the huge vessel was laid down so as to be launched sideways into the river and then to be floated on the tide. Brunel's plan for hydraulic launching gear had been turned down by the directors on the grounds of cost, an economy that proved false in the event. The sideways launch with over 4,000 tons of hydraulic power together with steam winches and floating tugs on the river took over two months, from 3 November 1857 until 13 January 1858. The ship was 680 ft (207 m) long, 83 ft (25 m) beam and 58 ft (18 m) deep; the screw was 24 ft (7.3 m) in diameter and paddles 60 ft (18.3 m) in diameter. Its displacement was 32,000 tons (32,500 tonnes).

The strain of overwork and the huge responsibilities that lay on Brunel began to tell. He was diagnosed as suffering from Bright's disease, or nephritis, and spent the winter travelling in the Mediterranean and Egypt, returning to England in May 1859. On 5 September he suffered a stroke which left him partially paralysed, and he died ten days later at his Duke Street home.

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