than 18 of the sun or 190 of the moon. Therefore by comparing the place of the moon's nodes with the place the sun will possess at the same time in the ecliptic: a tolerably near guess may be formed when an eclipse will happen. Example.What eclipses shall we have this year? PROBLEM XXI. To represent the Harvest Moon on the Celestial' Globe. Rule. This curious phenomenon is occasioned by our horizon becoming nearly parallel with the moon's orbit in Pisces and Aries. Therefore if the latitude of London be raised to the zenith, and six or eight patches bestuck on Pisces and Aries, at 13° distance (being what the moon passes through the heavens in twentyfour hours): these patches will all rise out of the horizon in nearly the same time, shewing that about the autumnal equinox,. when she is at the full in these signs, that she rises six or eight evenings with little more than an hour's difference of time. Patches placed at 13° distance on any other part of the ecliptic, will shew that she is an hour later in rising every day. Example.--Represent the Harvest Moon at London for September 16th. MISCELLANEOUS QUESTIONS, TO TRY HOW PERFECT THE PUPIL IS IN The Hour given that any Star comes to the Meridian, to find the Day of the Month, though it were lost.. Example.--If the pointers in the Great Bear come to the meridian at eleven o'clock at night, what day of what month is it? If y Draconis is perpendicularly over London at twelve at night, what day of what month is it? When y Draconis can be seen up a streight chimney in London at nine in the morning, what day of what month is it ? If the sun's meridian altitude at London be 31o 30', what day of what month is it? What time will the moon rise this day? In what parallel of north latitude doth the sun shine for one hundred and forty days with out setting? What place is forty degrees distance from London, in latitude 29° 50′ north? What day in August will be of the same length as the 10th May? At what hour on the 11th November will the sun be due east in London ? How many miles make a degree of longitude in latitude 51° 30'? If the altitude of Arcturus be 40°, and it bear upon E. S. E. point of the compass, what is its latitude? GEOGRAPHICAL AXIOMS. 1st, THE elevation of the pole above the ho rizon, is equal to the latitude of the place. 2d, The elevation of the equator above the horizon, is equal to the compliment of the latitude. 3d, Places situated on the equator have no latitude and those on the first meridian no longitude: so the place where that meridian intersects the equator has neither latitude nor longitude. : 4th, At the north pole which way soever the wind blows it is from the south and all places lie south of it. At the south pole all places lie north of it, and every wind comes from the north. 5th, All places on the earth have an equal portion of the sun's presence, and of his ab sence 6th, When the sun is on the equator, all places on the earth have equal day and night: but places on the equator have equal day and night all the year. 7th, Places on the same parallel of latitude will have their days and nights of the same length, whether long or short: but the nearer they are to the equator, the less will be that difference. 8th, Places within the tropics have the sun vertical twice in the year; those on the tropics but once, and to other places on the earth, never. 9th, The duration of twilight is the shortest in the torrid zone: longest in the frigid and on a medium in the temperate zone. : 10th, If a ship sails round the world, westward, the people in the ship will lose one whole day: i. e. they will reckon one day less than the people at the port they sailed from. But if they sail round the world eastward, they will gain one day. 11th, If two ships sail round the world, one east, and the other west, they would differ two whole days on their return, though they arrive on the same day. 12th, Every part of the earth's surface may be considered as its top.. For further information in Astronomy, Mr. WALKER's three last Lectures in his usal Course of Philosophy, and that on the EIDOURANION, are recommended. N. B.-Applications for Courses of Experimental Philosophy, to be made to Mr. D. F. WALKER, No. 5, Gloucester Street, Portman Square, London: Printed by SCHULZE & DEAN, 13, Poland Street. |