From 1770 to 1860 the pearl resources of Scotland remained almost dormant, and Scotch pearls were rarely met with in the markets. In 1861 a German merchant, who was acquainted with the beauty of these gems, traveled through the districts of Tay, Doon and Don, obtaining a great number which the poor people kept for their own pleasure, not esteeming them of any market value, and interested the fishermen in searching for the mussels. The seemingly high prices which he paid and the abundance of the pearls sent hundreds of persons to the rivers and small brooks. Those who were otherwise employed during the day devoted hours of the long summer nights to diligent search after the coveted shells; while boys and old persons, who were without regular avocations, waded day after day where there was a probability of reward. In the course of a short time pearls, good, bad and indifferent, reached the originator of the movement at Edinburgh, from Ayrshire, from Perthshire, and from the Highland regions far beyond the Grampians. He was soon the possessor of a collection which, for richness and variety, had seldom been surpassed. A trade in these gems was developed, the patronage of royalty was obtained, and once more Scotch pearls became fashionable, and their vogue was enhanced by the fondness which Queen Victoria entertained for them. In addition to the rivers named, pearls were found in the Forth, the Teith, the Ythan, and the Spey in eastern Scotland. The summer of 1862 was most favorable for pearling, owing to the dryness of the season and the low water, and unusually large quantities of pearls were found, the prices ranging ordinarily from 10s. to £2 6s. Queen Victoria is said to have purchased one for forty guineas; others were bought by Empress Eugénie and by the Duchess of Hamilton. A necklace of them was sold for £350 in 1863.[200] The value of the entire catch in Scotland in 1864 was estimated at £12,000 to the fishermen, the yield being unusually large in that season owing to the unprecedented drought which permitted access to the deep beds of the rivers. In some of the streams the resources were quickly depleted, but in others the fisheries yielded profitable returns for many years. While most of the pearls were small, some of them were choice and of considerable individual value, ranging from £5 to £150, and £500 is said to have been paid for one fine specimen. The pearl-mussel of the British Isles (_Unio margaritifera_) has a thick, coarse and unsightly shell, from 3 to 7 inches in width and 1½ to 2½ inches in length from the umbo to the lip. The rough exterior is dark brown, and it is sometimes twisted, distorted and barnacled.