See the complete document here

42 COSMOS.The perfectionin the graduation of the arc would have failedentirely, or to a considerable extent, in affording that greaterprecision of observation at vv^hich it aimed, if optical andastronomical instruments had not been brought into accord,and the correctness of vision made to correspond with thatof measurem 3nt. The micrometer-application of fine tlu'eadsstretched in the focus of the telescope, to wliich that instrumentowes its real and invaluable importance, was first devised,six years afterward (1640), by the young and talentedGascoigne.^While, as I have already observed, telescopic vision, observation,and measurement extend only over a period ofabout 240 years in the history of astronomical science, wefind, without including the epoch of the Chaldeans, Egyptians,and Chinese, that more than nineteen centuries haveintervened between the age of Timochares and Aristillusfand the discoveries of Galileo, during which period the positionand cou^Tse of the stars were observed by the eye alone,unaided by instruments. AYhen we consider the numerousdisturbances which, during this prolonged period, checked theadvance of cwilization, and the extension of the sphere ofideas among *,he nations inhabiting the basin of the Mediterranean,\y** are astonished that Hipparchus and Ptolemyshould have been so well acquainted with the precession ofthe equinoxes., the complicated naovements of the planets, thetwo principal inequalities of the moon, and the position of thestars ;that Copernicus should have had so great a knowledgeof the true Fystem of the universe and that ;Tycho Braheshould have been so familiar with the methods of practicalastronomy b-?fore the discovery of the telescope. Long tubes,272. Mfniu, ia his work, Scientia Longitudinum, which appeared in1G34, v/lritea .t^ follows: Applicatlo tuhi optlci ad alliidadam pro dellisfixis p-^ompte et accurate mensurandis a me excogitata est. Picard hadnot, up to the year 1667, employed any telescope on the mural circle:and Hevelius, when Halley visited him at Dantzic in 1679, and admiredtha precision of his measurement of altitudes, was observing throughImproved slits or * openings. (Baily's Catal. of Sfars, p. 38.)The unfortunate Gascoigue, whose merits remained so long unacknowledged,lost his life, when scarcely twenty-three years of age, atthe battle of Marston Moor, fought by Cromwell against the Royalists.See Derham, in the Philos. Transact., vol. xxx., for 1717-1719, p. 603-610. To him belongs the merit of a discovery which was long ascribedto Picard and Auzout, and which has given an impulse previously unknownto practical astronomy, the principal object of which is to determinepoii4ions in the vault of heaven.t Cosmos, vol. ii., p. 177, ITS.