As a ruler of like intellectual and scientific interests, the Castilian, Alfonso X, who lived in the thirteenth century, known as “The Wise” and as “The Astronomer,” deserves to be especially mentioned. By his order an elaborate astronomical work was prepared, which holds a place of first importance among mediaeval productions of its character. In this work the construction of globes is discussed in a very detailed manner, mention being made of every feature regarded as belonging to a properly constructed celestial sphere. So significant are certain chapters of this work for the history of globes and of globe making that a free translation is here given of that part relating to materials of which globes may be constructed.[88] “A sphere may be made of many materials,” says the author, “as of gold, or silver, or copper, or brass, or iron, or lead, or tin, or of a combination of these metals; or they may be made of stone, or clay, or wood. They may also be made of leather, of cloth, of parchment in many layers, and of many other materials which men employ when they wish to give an exhibition of their skill. Those, however, who have carefully considered these things, have decided that there is nothing more suitable than wood and for the following reasons. If the globe should be made of gold, only a very rich man would be able to possess it; furthermore it would be very heavy. If it should be made of thin sheets of gold it could be easily indented and would not long remain a perfect sphere. If it should be made small, that which was represented thereon would not appear distinct. The same thing may be said of silver, although it is a metal stronger than gold, as it is likewise harder, and therefore is not so easily indented. Copper is a metal harder than either silver or gold, but is so dry that it can not be easily fashioned into a globe, which should always be well made. Brass, which is like dark colored copper, may be more easily fashioned, because it is more malleable than copper, and is stronger than either gold or silver. If, however, a globe made of this material should be thin it might easily lose its shape, and if thick it would be very heavy. Of all metals, however, this is the one most suitable for use in making spheres, as it is the one most commonly employed. A globe of iron would be very difficult to make and would be very heavy, and since the rust would have to be removed from it very frequently, there would be much danger of destroying the figures. A globe of tin, if made of a thin sheet, could be easily indented, and would be very heavy if the sheet of which made were thick. Lead, if thin, would offer less resistance to injury than tin, and is a material much heavier. Furthermore, as lead is inclined to turn black, the figures and the stars represented on a globe of this material would soon become so discolored as to be no longer visible. There is no way by which it can be cleaned without wiping out the figures.