51 



II. 



NATURAL AND TELESCOPIC VISION. SCINTILLATION OF 



THE STABS. VELOCITY OF LIGHT. RESULTS OF PHO- 

 TOMETRY. 



THE increased power of vision yielded nearly two hundred 

 and fifty years ago by the invention of the telescope, has afforded 

 to the eye, as the organ of sensuous cosmical contemplation, 

 the noblest of all aids towards a knowledge of the contents of 

 space, and the investigation of the configuration, physical 

 character, and masses of the planets and their satellites. The 

 first telescope was constructed in 1608, seven years after the 

 death of the great observer, Tycho Brahe. Its earliest 

 fruits were the successive discovery of the satellites of Jupiter, 

 the Sun's spots, the crescent-shape of Venus, the ring of 

 Saturn as a triple planetary formation, (planeta tergeminus,) 

 telescopic stellar swarms, and the nebula? in Andromeda. l In 

 1634, the French astronomer, Morin, eminent for his observa- 

 tions on longitude, first conceived 'the idea of mounting a 

 telescope on the index bar of an instrument of measurement, 

 and seeking to discover Arcturus by day. 2 The perfection in 



1 See Cosmos, vol. ii. pp. 699-718, with notes. 



3 Delambre, Histoire de V Astronomic mcderne, torn. ii. 

 pp. 255, 269, 272. Morin, in his work, Scientia Longitu- 

 dinum, which appeared in 1634, writes as follows: Applicatio 

 tubi optici ad alhidadam pro stellis fixis prompte et accurate 

 mensurandis a me excogitata est. Picard had not, up to the 

 year 1667, employed any telescope on the mural circle ; and 

 Hevelius, when Halley visited him at Dantzic in 1679, and 

 admired the precision of his measurement of altitudes, was 

 observing through improved slits or openings. (Baily's CataL 

 of Stars, p. 38.) 



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