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nearest to that indicated by the hygrometer) is 1211, which, divided by 484 1 (the temperature of the air increased by 448) gives 2:501 for the weight in grains of the moisture contained in a cubic foot of the atmosphere at the time and place of the observation. The logarithmic working of this example is given in the margin.
It only remains to notice the column headed "Radiation." The "solar radiation' is the excess of the indication of a thermometer with a blackened bulb when exposed to the direct rays of the sun, above that of a similar thermometer placed in the shade, the indications being observed simultaneously. The "terrestrial radiation" is the defect of the indication of a thermometer with a blackened bulb when exposed during the night upon a grass plat to the full aspect of the sky, below that of a similar thermometer placed under shelter.
It must be borne in mind that the results recorded at the head of the several months are the averages of observations made in by-gone years, with which it is extremely improbable that similar observations made in the corresponding month of any one subsequent year will entirely agree, but from which on the other hand it is improbable that the departure will be very considerable.
Explanation of the columns headed" Length of day," "Day's increase or decrease,”
THE column headed "Length of day" contains the number of hours and minutes between sunrise and sunset. The column, headed 'Day's increase" expresses the number of hours and minutes which the day has increased since the shortest day; and, where the column is headed " Day's decrease," it expresses the number of hours and minutes which the day has decreased since the longest day; for example, the length of the longest day in 1842 is put down in the column "Length of day" at 16h. 34m.; and on the 6th of July following we find that the length of the day, or the number of hours and minutes between sunrise and sunset, is set down at 16h. 24m.; hence the day has decreased 10m. since the longest day, and, accordingly, in the column "Day's decrease," we find opposite July the 6th oh. 10m.
Equation of Time.
In the Almanacs of the Society the calculations are all made for mean time (given by the clock), instead of apparent time (given by the sun-dial), which latter had been used up to the year 1833. It must be obvious that, for all practical purposes, mean time is the most useful; and to obtain it from apparent time, the columns in the Almanac headed " Equation of Time" should be used, The column " Equation of Time" ought, for example, to be consulted when persons are desirous of setting their clock by a sun-dial. When clock after sun is written above the number of minutes and seconds opposite to the day, then the clock ought to be set so much slower than the sun-dial, and the contrary.
THE Moon's age is set down in days and the nearest tenths of days from the time of change. Thus it is New Moon on the 11th of January at 4h. 15m. afternoon, and therefore at noon on the 12th she is 19h. 45m. old, which is set down as eight-tenths. The fraction of the day of course continues the same throughout the lunation.
LIST OF THE CORRESPONDENCE OF ERAS WITH THE YEAR 1842. [In those Eras which begin with the Christian year, the year alone is stated; in those which begin at a different season, the month in which the 1st of January, 1842, occurs. is also given.]
Dioclesian, or of Martyrs
Seleucides, or Grecian
Death of Alexander
Era of Tyre
Caesarian of Antioch (Greek)
Era of Abraham
Spanish, or of the Cæsars
Persian Era of Yezdegird III. (Parsee account)
Armenian common year
25th Cohiac 1558 Audynæus 2153 3rd month of 2165 Audynæus 1966 Audynæus 1890 Canun II. 1889 4th month of 3857
2d Kaghots 1291 12th Kaghots 1290 18th Dhu'lkadah 1257 Poos or Margaly 4943
Fuslee (Bengal account)
36th year of 83rd cycle
20th day of 11th month of Sin chow, 73rd cycle
AUXILIARY TABLE FOR FINDING THE TIME OF SUN
RISING AND SETTING.
The time of Sunrise and Sunset in the 'British Almanac' is adapted to the parallel of latitude in which London is situated-viz. 51° 30′.
THE following table has been constructed to show the variations of time through the United Kingdom-namely, between the latitude of 58° and 50° 10′ N. The number of minutes found in this table under the month-day, and in the required latitude, are to be applied to the time of sun-rising and setting found on that day in the Almanac ; the result will be the time of his rising and setting at the place required.-Ex. At what time will the sun rise and set on May 21 at Edinburgh? The time of sunrise and sunset on that day in the Almanac is 4h. 2m. A.M., and Th. 51m. P.M. In the tables in parallel of 56°, in which Edinburgh is found, and under May 21, are 23 minutes; which, subtracted from 4h. 2m., leaves 3h. 39m. for time of sunrise; and, added to 7h. 51m., gives 8h. 14m. for time of sunsetting.
The places which follow the different parallels are situate within 15 miles of latitude, either north or south of it.
58° 0'-Dornoch, Tain, Dunrobin, Portenleik, Dunclaim.
57° 30'-Peterhead, Fraserburg, Banff, Elgin, Cromarty, Inverness, Applecross.
57° 0'-Aberdeen, Bervie, Braemar, Laggan, Cornock.
56° 30′-Forfar, Dundee, Perth, Comrie, Ardchattan.
56° 0'-Berwick, Haddington, Edinburgh, Linlithgow, Kinross, Stirling, Dumbarton, Glasgow.
55° 30′-Embleton, Jedburgh, Selkirk, Sanquhar, Lanark, Irvine, Ayr.
550 0'-Newcastle, Morpeth, Carlisle, Annan, Dumfries, New Galloway, Wigtown. 51° 30′-Scarborough, Whitby, Hartlepool, Stockton, Richmond, Appleby, Cockermouth, Whitehaven, North part of Isle of Man.
54° 0'-New Malton, York, Aldborough, Clitheroe, Lancaster, Preston.
53° 30'-Grimsby, Kingston-upon-Hull, Pontefract, Manchester, Wigan, Liverpool, Beaumaris, Holyhead.
53° 0'-Lynn Regis, Boston, Lincoln, Nottingham, Derby, Stafford, Flint, Chester, Denbigh, Caernarvon, Harlech.
52° 30'-Yarmouth, Norwich, Thetford, Ely, Peterborough, Leicester, Coventry, Lichfield, Shrewsbury, Ludlow, Montgomery, Aberystwith.
52° 0'-Ipswich, Colchester, Cambridge, Hertford, Bedford, Buckingham, Oxford, Gloucester, Worcester, Hereford, Monmouth, Brecon, Caermarthen, Cardigan, St. David's.
51° 30'-LONDON, Ramsgate, Canterbury, Rochester, Chelmsford, Windsor, Wallingford, Marlborough, Malmesbury, Bath, Bristol, Newport, Cardiff, Llandaff, Pembroke. 51° 0'-Dover, Winchelsea, Brighton, Guildford, Chichester, Winchester, Portsmouth, Southampton, Salisbury, Shaftesbury, Wells, Ilchester, Taunton, Bridgewater, Minehead, Barnstaple.
50° 30'-Newport (I. W.), Poole, Weymouth, Exeter, Ashburton, Totnes, Plymouth, Tavistock, Launceston, Bodmin, Camelford, Padstow.
50° 10′-Truro, Falmouth, Helstone, Penzance.
55° 0'-Carrickfergus, Antrim, Coleraine, Londonderry, Lifford, St. Johnstown. 54° 30'-Belfast, Killyleagh, Downpatrick, Armagh, Charlemont, Dungannon, Augler, Donegal, Ballyshannon, Enniskillen, Sligo.
54° 0'-Carlingford, Newry, Dundalk, Drogheda, Kells, Cavan, Belturbet, Carrick, Boyle, Castlebar, Killala.
53° 30′-Dublin, Swords, Naas, Athboy, Mullingar, Philipstown, Kilbeggan, Athlone, Roscommon, Lanesboro', Tulsk, Tuam, Ballinrob.
53° 0'-Wicklow, Blessington, Baltinglass, Carlow, Athy, Kildare, Portarlington, Maryboro', Ballynakill, Banagher, Galway, Ennis.
52° 30'-Newborough, Enniscorthy, Wexford, Kilkenny, Cullen, Clonmell, Cashell, Killmallock, Limerick, Askeyton.
52° 0'-Waterford, Dungarvon, Youghal, Tallagh, Lismore, Rathcormack, Cork, Marlow, Killarney, Tralee, Ardfast, Dingle.
51° 30'-Kinsale, Bandor, Clonekelty, Baltimore.
Morning. Afternoon. Morning. Afternoon.
Morning. Afternoon. Morning. Afternoon. Morning.