An Account of the Operations Carried Out for Accomplishing a Trigonometrical Survey of England and Wales: From the Commencement, in the Year 1784, to the End of the Year 1796, Begun Under the Direction of Royal Society, and Continued by Order of the Honourable Board of Ordance ; First Published In, and Revised From, the Philosophical Transactions, Volume 1W. Bulmer and Company, 1799 |
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Common terms and phrases
45 d Draconis 51 Draconis 85 Herculis Amplitude of arc angles April Arbury Hill axis azimuth circle Bardon Hill Barome Beacon Hill Blenheim brass Brill Butser Hill Canewdon Capella Castle Ring chain Corley Cygni Danbury degree Difference of latitude distance at Dunnose Distance from meridian distance Zenith distance Dover Court Dunnose Clifton Elmdon end of Base Epwell Face of limb Falkenham feet Flagstaff Gravesend Gringley Halstow Heathersedge Hern Hill Highclere horizontal Hornchurch Inches instrument July June Langdon Hill Lavenham length Line of collimation Longitudes Mean meridian meridional distance micrometer-screw Names of stations North observatory Observed Zenith Distance operation Orpit Peldon pendicular perpendicular placed plane Plate Pleshey Plumb plumb-line Point refr revolutions Rushmere screw Sept Severndroog Sheppey side South star Steeple Stoke telescope Thermometer Tillingham Trans triangles Ursa Ursæ White Horse Hill wire Zenith dist Zenith distance Barome Zenith distance Zenith Zenith Sector
Popular passages
Page i - Mudge's account of the operations carried on for accomplishing a trigonometrical survey
Page 110 - ... on each degree. A deviation of 8" from the true vertical, is a large quantity; nor can the cause of it be assigned, unless it be also supposed, that the matter producing that deflection extends in a southern direction beyond Arbury Hill. If the error, though not probable, as above observed, be supposed to exist at Dunnose, it must amount to more than 10"; and that too from the effects of attraction in a southern direction, where the deficiency of matter would lead us to believe the reverse would...
Page 110 - ... deflection existed at Dunnose; as the deviation of it towards the north, from a deficiency of matter towards the channel, would tend to diminish the inequality between the lengths of the two degrees. This will be evident, on consideration. I am therefore disposed to believe that the plumb-line...
Page 5 - ... running, almost every where, through a country abounding with hills, considerable both in magnitude and number. • Under this consideration, I determined to measure a portion of the meridian which proceeds from Dunnose to the mouth of the Tees ; because, from inquiry, I had reason to suppose it the longest meridional arc in Britain, free from any apparent obstruction. And I was led to select Dunnose for one of its extremities, as observations made there, in conjunction with others at Greenwich,...
Page 109 - From this measurement it appears, that the length of a degree on the meridian, in latitude 52° 2' 20", is 60820 fathoms. This conclusion is deduced from the supposition of the whole arc subtending an angle of 2° 50' 23",38 in the heavens, and a distance of 1036337 feet on the surface of the earth. The length of the degree at the middle point (51°...
Page 112 - In a future prosecution of this survey, the nuthor purposes to take the Zenith Sector farther northward, in order to ascertain whether the plum'j-Iine be really drawn towards the South. . He justly remarks that meridional operations, carried on in insular countries, are not so likely to afford just conclusions, with regard to the different lengths of the degrees, as the same operations conducted in places very remote from deep seas. This is a valuable paper ; and, being of national concern, it is...
Page 110 - I repeatedly verified the truth of the sector's position, by observing the transits of two stars, north and south of the zenith, at the greatest distances my arc would admit of. But, to return, if there be an error in the amplitude of the total arc, from a deflection of the plumb-line at either of the stations, it is not probable that any such deflection existed at Dunnose ; as the deviation of it towards the north, from a deficiency of matter towards the channel, would tend to diminish the inequality...
Page 32 - Trans. 1 803), and thence for the whole apparatus, a firm foundation, I caused four long stakes to be driven into the ground, (one for each foot of the stand,) to which its feet were firmly screwed down. The surfaces of the stakes were cut off smooth, and brought into the same horizontal plane, by which means the interior frame and sector were placed much within the limits of their several adjustments," The whole was inclosed in a suitable observatory.
Page viii - That 61 182 fathoms is, very nearly, the length of a degree of a great circle perpendicular to the meridian in latitude 50° 41', cannot be doubted, since the observations at Dunnose and Beachy Head (Art.
Page vii - Exposé des opérations faites en France en 1787, pour la jonction des observatoires de Paris et de Greenwich.