But the repeal of the duty on glass, and of the tax upon windows, has had the effect of improving the architecture of our houses to a degree which no one would have thought possible who had not studied how the operation of a tax impedes production. We have now plate-glass of the largest dimensions, giving light and beauty to our shops; and sheet-glass, nearly as effective as plate, adorning our private dwellings. Sheet-glass, in the making of which an amount of ingenuity is exercised which would have been thought impossible in the early stages of glass-making, is doing for the ordinary purposes of building what plate-glass did formerly for the rich. A portion of melted glass, weighing twelve or fourteen pounds, is, by the exercise of this skill, converted into a ball, and then into a cylinder, and then into a flat plate; and thus two crystal palaces have been built, which have consumed as much glass, weight by weight, as was required for all the houses in one-fourth of the area of Great Britain in the beginning of the century. [Illustration: Plate-glass Factory.] There are two kinds of pottery--common potters' ware, and porcelain. The first is a pure kind of brick; and the second a mixture of very fine brick and glass. Almost all nations have some knowledge of pottery; and those of the very hot countries are sometimes satisfied with dishes formed by their fingers without any tool, and dried by the heat of the sun. In England pottery of every sort, and in all countries good pottery, must be baked or burnt in a kiln of some kind or other. Vessels for holding meat and drink are almost as indispensable as the meat and drink themselves; and the two qualities in them that are most valuable are, that they shall be cheap, and easily cleaned. Pottery, as it is now produced in England, possesses both of these qualities in the very highest degree. A white basin, having all the useful properties of the most costly vessels, may be purchased for twopence at the door of any cottage in England. There are very few substances used in human food that have any effect upon these vessels; and it is only rinsing them in hot water, and wiping them with a cloth, and they are clean. The making of an earthen bowl would be to a man who made a first attempt no easy matter. Let us see how it is done so that it can be carried two or three hundred miles and sold for twopence, leaving a profit to the maker, and the wholesale and retail dealer. The common pottery is made of pure clay and pure flint. The flint is found only in the chalk counties, and the fine clays in Devonshire and Dorsetshire; so that, with the exception of some clay for coarse ware, the materials out of which the pottery is made have to be carried from the South of England to Staffordshire, where the potteries are situated. The great advantage that Staffordshire possesses is abundance of coal to burn the ware and supply the engines that grind the materials.