A furnace on the old plan consumed 2575 bushels of coal weekly, and refined only 38,000 pounds of raw material. The new refined 35,000 pounds, with a consumption of only 2000 bushels of coal. Since then a further decrease in consumption of coal has been produced by the use of the Delano patent, which feeds the furnace by forcing up the coal at the bottom of the burning mass, thus consuming the entire smoke, and obviating the necessity of wheeling coal on the glass-house floor and impeding the workmen. It also does away with all danger to the pots in feeding the fires. Besides these great advantages, it distributes a regular and uniform heat to each pot, causing the pots to last much longer, and fusing the metal better,--important items to mixers. From three to five tons of fuel is the weekly saving in a first-class furnace. It is of vital importance to obtain pots that will last a reasonable time. Clays of the finest quality are essential. Each piece must be freed from any foreign matter, particularly sulphate of iron, which often occurs. The burnt and raw clay should be well mixed, wet, and frequently kneaded, or trod over by the naked feet. Tenacity must be secured, sufficient that a roll twelve to eighteen inches long can be suspended, and hold firmly together by its own adhesiveness. The next point is to make the pots free from air blisters, all portions being compact; then to dry them thoroughly, which requires great care on account of the inequality of the different parts. Pot-makers are not agreed as to the value of different clays, and the use and proportion of raw to burnt shells. Some use sixteen parts raw to eleven burnt, some fifty-five raw to forty-five burnt, some equal proportions of each. Manufacturers have mainly depended upon imported clays, but the Western glass-makers have used Missouri clay with success. In the east it has not yet come into general use. Of the imported, that from Stowbridge is considered best. Garnkerk is a strong clay, and, if well selected, will rival any other. The analyses are for STOWBRIDGE, Silica, 64 parts, Alumina, 20 " Lime, 1 " Iron, 3 " GERMAN, Silica, 46 parts, Alumina, 34 " Iron, 3 " GARNKERK, Silica, 53 parts, Alumina, 43 " Lime, 1 " Iron, 1 " FRENCH, Silica, 40 parts, Alumina, 31 " Iron, 3 " WESTERN, Silica, 49 to 52 parts, Alumina, 31 to 32 " Iron, 2 to 4 " FUEL. This subject deserves special notice. We have said that the New England manufacturers at first used wood only, which was prepared by being split into equal lengths, with an average diameter of two inches, and then kiln-dried to dispel the sap and moisture. This fuel was supplied to the furnace at opposite fire-holes, a stick at a time, which was a laborious and heating process.