Umber, or Grayling, Salmo thymolus, L. a species of the salmon, which frequents rapid, clear streams, and particularly those flowing through mountainous countries. It inhabits principally the rivers of Derbyshire, and those of Scot and; though it is occasionally caught in the stream near Christ-church, Hants. This fish seldom exceeds 16 inches in length, and weighs from 2 to 3 1/2 lbs. : it is of an elegant form, somewhat resembling the trout, but of a lighter colour.
The umber is remarkable for its velocity in swimming : the proper season for angling is in the months of March and April, when this fish may be easily taken with a strong line and hook ; as it is exceedingly voracious, and will eagerly take a bait. - Its flesh is very delicate; and its intestines are employed by the Laplanders as a substitute for rennet, to coagulate the milk of the rein-deer.