The practical handicraft of these imported expert dairymaids was supplemented and regulated by the scientific work of Professor Segelcke and his pupils and from the Sixties buttermaking became an art in Denmark which was subjected to the most searching study and improvements. Danish butter soon captured the English market where previously Isigny (from Northern France) and Dutch butter had commanded the highest prices, and Danish sweet butter put up in sealed tin cans also became known all over the world as the only butter that would stand export to the Tropics. In this country Orange County, N.Y., first produced a high-class article and, later, Elgin, Ill., became the center that stood for the top of perfection. Thence the industry soon spread over the middle western states, largely populated by Scandinavian immigrants many of whom were skilled buttermakers, educated in the old countries. Even up to this day it is noticeable that the list of prize winning buttermakers at the National Dairy Shows and other exhibitions is largely made up of Scandinavian names. In Minnesota, for instance, as fine butter is now made as anywhere in the world. _Dairy Butter._—In the early days of the industry butter was made at home on the farm. The milk was set in shallow vessels,—in the Holstein and Danish dairies in wooden tubs 24 inches in diameter placed on the stone or concrete floor in the milk-vault, a cool cellar partly underground,—or in tin pans on the pantry shelf. After 36 to 48 hours the cream was skimmed off with a flat scoop, often both cream and skim milk being sour. About 1860 the deep tin can was introduced, set in cold running water or, where ice was available, in ice water. This was a great improvement over the shallow setting system. It was now possible to raise most of the cream in 24 hours leaving not to exceed ½% butter-fat in the skim milk, and to have both cream and skim milk sweet. _Centrifugal Creaming._—But the climax of perfection was not reached until the separator (see under Cream) was invented about 1879 and cream was raised instantaneously. For a long time it was the object of the manufacturers to produce _power separators_ of larger and larger capacity, handling from 6,000 to 10,000 lbs. of milk an hour.