lay in the warnings derived from such computations, which should enable
the believer to avoid threatened calamities. In 1575 he left Denmark
once more and made his way to Cassel, where he found a kindred spirit in
the studious Landgrave, William IV. of Hesse, whose astronomical
pursuits had been interrupted by his accession to the government of
Hesse, in 1567. Tycho observed with him for some time, the two forming a
firm friendship, and then visited successively Frankfort, Basle, and
Venice, returning by way of Augsburg, Ratisbon, and Saalfeld to
Wittenberg; on the way he acquired various astronomical manuscripts,
made friends among practical astronomers, and examined new instruments.
He seemed to have considered the advantages of the several places thus
visited and decided on Basle, but on his return to Denmark to fetch his
family with the object of transferring them to Basle, he found that his
friend the Landgrave had written to King Frederick on his behalf,
urging him to provide the means to enable Tycho to pursue his
astronomical work, promising that not only should credit result for the
king and for Denmark but that science itself would be greatly advanced.
The ultimate result of this letter was that after refusing various
offers, Tycho accepted from the king a grant of the small island of
Hveen, in the Sound, with a guaranteed income, in addition to a large
sum from the treasury for building an observatory on the island, far
removed from the distractions of court life. Here Tycho built his
celebrated observatory of Uraniborg and began observations in December,
1576, using the large instruments then found necessary in order to
attain the accuracy of observation which within the next half-century
was to be so greatly facilitated by the invention of the telescope. Here
also he built several smaller observing rooms, so that his pupils should
be able to observe independently. For more than twenty years he
continued his observations at Uraniborg, surrounded by his family, and
attracting numerous pupils. His constant aim was to accumulate a large