As soon as the plants are in a sufficient state of maturity, they are gathered. The leaves are picked off, and submitted to the action of mills, somewhat similar to the mills that are used for the grinding of oak-bark. In these they are reduced to a pulp. The woad is then laid in small heaps, which are closely and smoothly pressed down. After continuing about a fortnight in this state, the heaps are broken up, and their substance is formed into balls, which are exposed to the sun to be dried. When the balls are perfectly dry, they are ready for use; and are employed, not only in dyeing blue, but also as the basis of several other colours. 185. _HORSE-RADISH_ (Cochlearia armoracia) _is a well-known kitchen-garden plant, which grows wild by the sides of ditches and the banks of rivers, in several parts of the north of England._ The _root_ of horse-radish is much used for culinary purposes. It is remarkable for great pungency both of smell and taste. When scraped, it is mixed with pickles to heighten their flavour, and is eaten with roast beef, fish, and several other kinds of food. Whenever more of the roots are dug out of the earth at once than are immediately wanted, they may be preserved for some time, in a juicy state, by putting them into dry sand. Horse-radish is also in considerable repute as a medicine, and is a powerful stimulant, whether externally or internally applied. Notwithstanding this, we are informed by Dr. Withering, that an infusion of horseradish in cold milk is one of the best and safest cosmetics that are known. SILIQUOSA. 186. _COMMON MUSTARD is made from the powdered seeds of a plant_ (Sinapis nigra), _which grows wild in corn-fields and by road sides, in most parts of England, and is known by its yellow cruciform flowers, with expanding calyx, and its pods being smooth, square, and close to the stem._ In light and otherwise barren lands mustard is cultivated to great advantage. That which is produced in the county of Durham has much celebrity; though the powdered seeds of charlock have, in many instances, been substituted, and sold in place of it. Mustard is in daily use at our tables, and the _seeds_, whole or bruised, are employed in pickles, and for numerous other culinary purposes. These seeds yield, on pressure, a considerable quantity of oil, which is soft and insipid to the taste, and partakes but little of the acrimony of the plant. Different preparations of mustard are sometimes used in medicine. The seeds, taken internally, are serviceable in asthma, rheumatism, and palsy. Cataplasms of mustard are employed, on account of its stimulating properties, on benumbed or paralytic limbs. An infusion of the powdered seeds, taken in considerable quantity, operates as an emetic, and, in smaller quantity, is an useful aperient and diuretic.