316 GEOGRAPHY AND ASTRONOMY. would therefore know the sun'sdeclination, supposeat six o'clock in the morning of any given day, you must compare the declina- tion for that day with the sun's declination the foregoingday, and make a proportionable allowance, viz. three-fourth parts of the difference of these two declinations. If at six in the afternoon, you must compare it with the following day, and allow in the same manner one- fourth part. II. These tables are fitted for the meridian of London. If you would know therefore the sun's declination the same day at noon at Port Royal in Jamaica, you must consider the difference of longitude. Now that place being about 75 degrees westward from London, that is, five hours later in time, it is but seven o'clock in the morning there when it is noon at London; and you must make a proportionable allowance for the difference of the sun's declination by comparing it with that of the foregoing day. If that place had the same longitude eastward from London, it would be five o'clo'ck in the afternoon there ; and then you must compare the sun's present declination with that of the day follow- ing, and make allowance for the five hours, i. e. almost of the difference of the two declinations. But if you would know the sun's declination at any place, and at any hour of the day at that place ; find what hour it is at London at the given hour at that place, and find the declination of the sun for that hour at London by note the first. Note, These allowances must be added or substracted ac- cording as the sun's declination is increasing or decreasing. Yet in any of these geometrical operations the difference of the sun's declination at other hours of the day or at other places of the world is so exceeding small that it is not sufficient to make any remarkable alterations, except when the sun is near the equinoxes ; and then there may be some allowances made for it in the mannerI have described ; nor even then is there any need of any such allowances except in places which differ from Lon- don near 5 or 6 hours in longitude. III. Let it be noted also, that as the place of the sun, so consequently his declinationand right ascension for every day do vary something every year by reason of the odd five hours and forty-nine minutes over and above 365 days, of which the solar year consists. Therefore it was proper to represent the sun's declination every day for four years together, viz. the three years before leap-year, and the leap-year itself. For in the circuitof those four years the sun returns very nearly to the same declina- tion again on the same day of the year, because those odd five hours-and 49 minutes do in four years time make up 24 hours, or a whole day (wanting but four times eleven, i. e. 44 minutes;) which day is super added to the leap-year, and makes the 29th of February, as bath been said before.
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