Another kind of plate glass, called "patent rolled plate," is made by ladling out from a pot molten glass in the proper state of consistence. The ladle is brought over a small glass table, and a similar operation is performed to that already described. This patent rolled plate is sometimes made with grooves on one of its surfaces, or with patterns in imitation of diamond quarry glazing, and, in fact, with any designs, according to the taste of the manufacturer. These designs are all engraved upon the table, and communicate their patterns to the soft glass; but the smooth surface of such glass which comes in contact with the roller is slightly undulating, though polished. This method of glass making was invented and patented by Mr. Hartley, the noted manufacturer, of Sunderland. A lighter kind of plate glass, which is principally used for glazing the better class of pictures and engravings, and called "patent" plate, is simply sheet glass polished after the manner of plate glass. Crown glass, which only admits of being cut into small squares, is also used for picture glazing, but is more carefully prepared, and is called by the name of "flatted crown." _Looking Glasses._--Plate glass is employed for making looking glasses, and two processes are now in use for silvering them, the first of which consists in applying a sheet of tinfoil saturated with quicksilver to one side of the glass. The operation is conducted as follows: on a perfectly smooth table a sheet of stout tinfoil is laid, and on it is poured quicksilver, which is distributed evenly over the surface with a hare's foot. When the whole sheet is amalgamated with the quicksilver, more of that substance is poured over it, until it flows quite freely. The glass plate to be silvered, having been made perfectly clean, is floated upon the surface of the quicksilver, an operation requiring care, and is then covered all over with weights, by which means the excess of quicksilver is pressed out, and the glass comes in contact with the amalgamated sheet of tinfoil, to which it adheres entirely. This ancient method of silvering glass has some advantages over the one next to be described. The colour of the plate is, according to artistic taste, better, and with care the plate will not lose its brilliancy for years. I have in my possession some old glasses, the silvering of which is very beautiful, except where it has suffered from mechanical injuries. Silver can be precipitated from a solution of nitrate of silver in several ways, and in some of these specimens was like a bright film. If a crystal of nitrate of silver be put into a test-tube with some bitartrate of lime, and the mixture be rendered ammoniacal and gently warmed (it being kept in motion during the experiment), its sides will be covered with a very brilliant deposit of metallic silver. Oil of cloves and grape sugar have also the power of reducing metallic silver from ammoniacal solutions of the