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358 equal to ± 45″, the collimation error being − 114″.6. These results are sufficient to show that Tycho's instruments were really made with the great care which he declares he had always bestowed on them, and in connection with the above results as to Tycho's standard stars, they exhibit the vast stride forward which observing astronomy made at Uraniborg, and which but for the invention of the telescope could hardly have been much exceeded by his successors.

It will not be out of place to say a few words here about a time-honoured absurdity which has attributed great carelessness to Tycho Brahe in the adjustment of his instruments in azimuth. In 1671, Picard, when determining the latitude of Uraniborg, measured the azimuths of the principal church spires in Seeland and Scania visible from the site of Uraniborg. At Copenhagen he found among Tycho's manuscripts similar observations which showed considerable differences from his own. Picard did not lay any stress on this discrepancy when mentioning it in the account of