Antoine Hamilton, in his _Gaufrey_--a parody on _The Thousand and One Nights_--tells of a Saracen princess, _Fleur d'Epine_, who, before she was fifteen years of age, was able not only to speak Latin and Romance, but who was also "better acquainted than any woman in the world with the movements of the stars and the moon." "Et du cours des etoiles et de la lune luisant Savoit moult plus que fame de chest siecle vivant." If any woman between the time of Hypatia and Galileo deserved such high praise for her astronomical knowledge it was certainly Saint Hildegard, the famous Benedictine abbess of Bingen on the Rhine. She has well been called "the marvel of the twelfth century," not only on account of her sanctity, but also on account of her extraordinary attainments in every branch of knowledge then cultivated. When treating of the sun, Hildegard tells us that it is in the center of the firmament and holds in place the stars that gravitate around it, as the earth attracts the creatures which inhabit it. This view of a twelfth century nun is indeed remarkable. For, in her time, the earth was by everyone considered as the center of the firmament, while universal gravitation--the sublime discovery of Newton--had not as yet entered into the scientific theories of that epoch. Hildegard likewise anticipates subsequent discoveries regarding the alternation of the seasons. "If," she writes, "it is cold in the winter time on the part of the earth which we inhabit, the other part must be warm, in order that the temperature of the earth may always be in equilibrium." That she should have arrived at this conclusion before navigators had visited the southern hemisphere is truly astonishing.[135] "The stars," she continues, "have neither the same brightness nor the same size. They are kept in their course by a superior body." Here again is her idea of universal gravitation. These stars, she further declares, are not immovable, but they traverse the firmament in its entirety. And to make clearer her conception of the motion of the stars, she compares this motion to that of the blood in the veins. To hear one of this early period speaking of blood coursing through the veins and thus traversing the whole body of man seems to presage, in a remarkable manner, the beautiful discoveries of Cesalpino and Harvey regarding the circulation of the blood. The most celebrated astronomer of the early Renaissance was John Mueller, of Koenigsburg, better known as Regiomontanus. In his observatory in Nuremberg he was ably assisted by his wife who exhibited a special interest in astronomy. At the end of the sixteenth century, Sophia Brahe, the youngest sister of Tycho Brahe, following in the footsteps of her illustrious brother, attained great celebrity as an astronomer.