Rigaud mountain is situated in the northwestern part of the county of Vaudreuil, Province of Quebec, Canada, and includes in its area the parish of Saint George and parts of the parishes of Rigaud, Saint Redempteur, and Sainte Marthe. It is the most western of a line of hills of igneous origin, which, in the vicinity of Montreal, forms the principal topographic feature of the eastern part of the Paleozoic plain of central Canada. These hills—locally termed mountains—are at no great distance from the border of the V-shaped Laurentian protaxis, and follow a line of disturbance which is almost at right angles to the trend of the Notre Dame range. In westward succession there are Shefford, Yamaska, Rougemont, Beloeil, Montarville, Mount Royal, and Rigaud. The hills of Brome, lying south of Shefford, and mount Johnson, south of Beloeil, are on another line, but evidently belong to the same series. . . .