avillas del Orbe, published in 1286.
A passage in the Spanish Leyes de las Partidas of the middle of the thirteenth century runs as follows: The needle which guides the mariner in the dark night, and shows him how to direct his course both in good and bad weather, is the intermediary between the loadstone and the North Star.
Dante, about 1300, refers to the needle which points to the star.
Marco Polo, the great traveler, was in the service of Kublai Khan, the conqueror of China, from 1274 to 1291, and was concerned in the introduction of the compass from China to Europe direct.
It had previously arrived by the good old channel, India and Arabia; but Marco Polo did not know that, and his services can hardly be exaggerated.
The Arabs sailed by the compass during the Khalifate of Cordova, which lasted till A. D. 1237, when it was subdued by the Moors.
An authority states that it was known in Norway previous to 1266.
Dr. Gilbert, physician to Queen Elizabeth, states that P
se names) are both derived from feldspar, which consists of silica, alumina, and potash.
Kaolin consists of decomposed feldspar, and petuntse is the powder of undecomposed feldspar.
The radical difference seems to be that by decomposition and exposure to the air the kaolin has acquired plasticity, has become a clay. This being the case, it is easy to conceive the propriety of keeping the prepared clay in a condition to improve by exposure and age, before working it. Marco Polo, who was from 1274 to 1291 in the service of Kublai Khan, the Conqueror of China, states that the heaps of porcelain clay were exposed in China for thirty to forty years before using; so that men gathered the materials for their children and grandchildren.
The other material mentioned is hoache, and probably, as the Pere d'entrecolles remarks, is steatite; which is a compound of silica and magnesia.
We cannot go into all the particulars of the history of the art, nor describe the ingredients and compositi