William took a leading part in safeguarding the Lutheran Reformation, and was indefatigable in his endeavours to unite the different sections of Protestantism against Catholicism.

As an administrator he displayed rare energy, issuing numerous ordinances, appointing expert officials, and in particular ordering his slender finances.

It should be noticed that clocks, on which Tycho depended very little, were used at Kassel for finding the difference of right ascension between Venus and the sun before sunset.

[1] The Hessian star catalogue was published in Historia coelestis (Augsburg, 1666) by Albert Curtz, and a number of other observations are to be found in Coeli et siderum in eo errantium observationes Hassiacae (Leiden, 1618), edited by Willebrord Snell.

45 (Vierteljahrsschrift der naturforschenden Gesellschaft in Zurich, 1878), has given a resume of the manuscripts still preserved at Kassel, which throw much light on the methods adopted in the observations and reductions.