After Mamun (A.D. 812-833) the most intellectual Khalif appears to have been Radhi-billah (A.D. 934-940). His poems were collected in a Diwan. He was the last Khalif who presided not only over the Government as a sovereign, but also over the pulpit as Imam; indeed, he may be said to be the terminal point of the power, brilliancy and independence of the house of Abbas, which henceforth gradually declined till its final extinction with the conquest of Baghdad by the Mughals in A.D. 1258. The great chess-player, Abu-bakr as Sauli, bears witness, in Masudi's 'Meadows of Gold,' to the great accomplishments of Radhi-billah, and to his love of the sciences. Of games, chess and nerd[4] flourished during his reign, and although the perfection of song and of lute-playing had already passed away, singers and musicians are still mentioned. Of the amusements of the court, hunting appears to have flourished most, and the learned poet Koshajim, who wrote on the game of nerd, also left instructive poems on the chase. Radhi-billah appears to have been fond of books of travel and of natural history, and of the society of men of letters and of science, and liked listening to recitals on the history, politics, and glory of the old Persian kings. [Footnote 4: Nerd.--This game is mentioned as early as the Shah-Namah, the author of which, Firdausi, was of opinion that it is of genuine Persian, and not of Indian origin, like chess, but this assertion is not necessarily correct. Hyde has described the game in his 'Historia Nerdiludii,' and it resembles somewhat the German puff and triktrak, and the English backgammon. It is played on a board divided into black-and-white compartments, with a black and a white house in the centre. The moves are made according to the numbers that come up on the throw of two dice.]