Until 644 the island was exceedingly prosperous, but in that year began the period of Arab invasions, which continued intermittently until 975.
These two things are done simultaneously by heating and melting the ore in contact with coke, charcoal or anthracite, in the iron blast furnace, from which issue intermittently two molten streams, the iron now deoxidized and incidentally carburized by the fuel with which it has been in contact, and the mineral matter, now called " slag."
The district of Hofrat-el-Nahas (the copper mine) is rich in copper, the mines having been worked intermittently from remote times.
Again, the states, intermittently convoked according to the kings good pleasure, exercised neither periodical rights nor effective control, but fulfilled a duty which was soon felt as onerous.
The two adversaries had each the same scheme of government: each wanted to take charge of Charles VI., who was intermittently insane, and to exclude his rival from the pillage of the royal exchequer; but this rivalry of desires brought them into opposition on all the great questions of the daythe war with England, the Great Schism and the imperial election.