The work is a treatise on the sphere, written in dialogue form, dealing chiefly with astronomy but including some geographical information. Recorde's writings exhibit a marked bias in favour of mathematics, but they also reflect strong traditions which Recorde, in common with most educated people of his time, found difficult to discard. These Aristotelian and Ptolemaic traditions postulated that the sub-lunary realm, the seat of the base elements, was subject to change and corruption; in contrast, the heavenly or celestial realm was necessarily pure, immutable and eternal. It is in this book that Recorde provides the English reading public with the first significant reference to the heliocentric theories of Nicholas Copernicus.