Medieval meteorological manuscript. 1230 extract from De sphaera mundi,by the Parisian astronomer and monk Johannes de Sacrobosco (circa 1195-1256),with a circular chart correlating directions,winds,elements,seasons,temperaments,qualities,and ages. De sphaera mundi is a short astronomy textbook that was widely read and influential in Europe as an introduction to astronomy. Sacrobosco is also known for writing a short introduction to the Hindu-Arabic numeral system,which became the most widely read introduction to the subject in the later mediaeval centuries. He also correctly described the defects of the then-used Julian calendar and recommended what was essentially the Gregorian calendar |