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 store of observations of a high order of accuracy, and thus to provide data for the complete reform of astronomy.  As we have seen, few of the Danish nobles had any sympathy with Tycho’s pursuits, and most of them strongly resented the continual expense borne by the King’s treasury.  Tycho moreover was so absorbed in his scientific pursuits that he would not take the trouble to be a good landlord, nor to carry out all the duties laid upon him in return for certain of his grants of income.  His buildings included a chemical laboratory, and he was in the habit of making up elixirs for various medical purposes; these were quite popular, particularly as he made no charge for them.  He seems to have been something of a homoeopathist, for he recommends sulphur to cure infectious diseases “brought on by the sulphurous vapours of the Aurora Borealis”!

King Frederick, in consideration of various grants to Tycho, relied upon his assistance in scientific matters, and especially in astrological calculations; such as the horoscope of the heir apparent, Prince Christian, born in 1577, which has been preserved among Tycho’s writings.  There is, however, no known copy in existence of any of the series of annual almanacs with predictions which he prepared for the King.  In November, 1577, appeared a bright comet, which Tycho carefully observed with his sextant, proving that it had no perceptible parallax, and must therefore be further off than the moon.  He thus definitely overthrew the common belief in the atmospheric origin of comets, which he had himself hitherto shared.  With increasing accuracy he observed several other comets, notably one in 1585, when he had a full equipment of instruments and a large staff of assistants.  The year 1588, which saw the death of his royal benefactor, saw also the publication of a volume of Tycho’s great work “Introduction to the New Astronomy”.  The first volume, devoted to the new star of 1572, was not ready, because the reduction of the observations involved so much research to correct the star places for refraction, precession, etc.; it was not completed in fact until Tycho’s death, but the second volume, dealing with the comet of 1577, was printed at Uraniborg and some copies were issued in 1588.  Besides the comet observations it included an account of Tycho’s system of the world.  He would not accept the Copernican system, as he considered the earth too heavy and sluggish to move, and also that the authority of Scripture was against such an