MAYO, a county of Ireland, in the province of Connaught, 62 miles in length, and 52 in breadth, bounded on the east and north-east by Roscommon, by Sligo on the west, by the sea on the north, and by Galway on the south. The air is moist and cold, especially upon the mountains, where also the soil is poor and coarse; but in other parts the pasturage is good, with herds of cattle and deer, &c. In this county is a fresh-water lake called Lough mask, about 11 miles long, and five broad, abounding with fish, particularly salmon. Hereabouts were formerly seated the Galloglasses, a people descended from the Scots of the western isles, who used to fight in coats of mail with two-edged battle-axes. The principal town is also called Mayo, which was formerly a bishop's see; but the bishopric has since been annexed to Tuam. It is now much decayed, but gives the title of viscount to the family of Bourke. W. Long. 9. 39. N. Lat. 53. 40.