In August, 1900, several specimens of this mineral were found attached to gypsum-rock supplied to me from the quarry at Kirkby There, in Westmoreland, by Messrs. Joseph Robinson & Co., Ld., of Carlisle, who kindly inform me that the bed of this rock is about 20 feet thick, being overlaid by about 22 feet of marl, &c. There is very little anhydrite, not more than 2 or 3 inches, which, as a rule, is found in the middle of the bed of gypsum. Although I have used this rock for commercial purposes for years past in regular quantities, yet the mirabilite was never previously noticed.