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Show A GREAT STAR MAP : Kov Making by t e Observtorfe-' of . the World. At a congress held at Paris in 18S7, it was decided that the end of the ' nineteenth century should see the making of a great catalogue of all the stars in the sky, upon a scale of enm---fl iiui precision surpassing any-t any-t thing previously attempted. ; It is im- possible, to exaggerate the importance of such a work; for upon our star catalogues cat-alogues depends ultimately the entire structure of astronomical science. The work was far too vast for the powers of any one observatory. Therefore the whole sky, from pole to pole, was divided into eighteen belts or zones oi approximately equal area'; and. each ol these was assigned to ,a single observatory observ-atory to be photographed. A series of telescopes were specially constructed construct-ed so that every part of the work !'?-should be done with the same type ol instrument. As far as possible, an attempt at-tempt was made to secure uniformity of methods, and particularly a uniform scale of precision. To cover the entin sky upon the plan proposed, no less than forty-four thousand one hundrec and eight negatives are required; and most of these have now been finished fin-ished The further measurement ol the pictures and the drawing up of a vast printed star catalogue are also well under way. One of the participating partici-pating observatories, that of Potsdam Germany, has just published the firs volume of its part of the catalogue. It is estimated that this observatory alone will require twenty quarto volumes to contain merely the final results re-sults of its work on the catalogue. Altogether Al-together not less than two million stars will find a place in this, our latest directory di-rectory of the heavens. Exchange. |