They sailed thence by a canal into the Red Sea, and this statement proves the accuracy of Dicuil, for this canal really existed and continued in use until 767, when it was closed to hinder the people of Mecca and Medina getting supplies from Egypt. The account of the Pyramids is particularly interesting. "The aforesaid Brother Fidelis measured one of them and found that the square face was 400 feet in length." The same brother wished to examine the exact point where Moses had entered the Red Sea in order to try if he could find any traces of the chariots of Pharaoh or the wheel tracks, but the sailors were in a hurry and would not allow him to go on this excursion. The breadth of the sea appeared to him at this point to be about six miles. Dicuil describes Iceland long before it was discovered by the Danes. "It is now thirty years," said he, writing in 825, "since I was told by some Irish ecclesiastics, who had dwelt in that island from the 1st of February to the 1st of August, that the sun scarcely sets there in summer, but always leaves, even at midnight, light enough to do one's ordinary business--_vel pediculos de camisia abstrahere_"! Those writers are greatly mistaken, he says, who describe the Icelandic sea as always frozen, and who say that there is day there from spring to autumn and from autumn to spring, for the Irish monks sailed thither through the open sea in a month of great natural cold, and yet found alternate day and night, except about the period of the summer solstice. He also describes the Faroe Isles:-- "A certain trustworthy monk told me that he reached one of them by sailing for two summer days and one night in a vessel with two benches of rowers.... In these islands for almost a hundred years there dwelt hermits who sailed there from our own Ireland [nostra Scottia], but now they are once more deserted as they were at the beginning, on account of the ravages of the Norman pirates." This is proof positive that the Irish discovered and inhabited Iceland and the Faroe Islands half a century or a century before the Northmen. Dicuil was distinguished as a grammarian, metrician, and astronomer,[15] but his geographical treatise, written in his old age, is the most interesting and valuable of his achievements.