In practice, however, the regenerators are only used whilst the batch materials are being melted during the night, and by morning, when the metal is melted and “plain,” the heat is brought back, or retarded, by using the gas from the gas producers and cool atmospheric air under natural draught, instead of the regenerated hot air. This cooler mixture, naturally not being so active in combustion, maintains just sufficient temperature for working the metal out during the day. Later in the day, when the pots are emptied and refilled with batch, the regenerators are re-connected and the founding proceeds again through the night, and the metal is again got ready for the workmen coming in next morning. It will be seen that this method of melting and working out the metal does away with night work, the furnace man alone remaining in charge during the night. All firing is done outside the glass furnace room, which is well lighted, clean, and free from coal dust, totally different conditions from those existing in many English glass houses of to-day. A Siemens Siegbert furnace taking ten open crucible pots, and filled each day, turns out 15 to 18 tons of metal a week. The crucibles are about 30 in. in diameter and have a capacity of 5-1/2 cwts. of metal each. The amount of fuel consumed is about 18 tons a week. This type of furnace costs about £1,600 to £2,000 to build. In the miter’s opinion, a disadvantage of this furnace is that, during the reversing in the direction of the fire gases, the greatest heat is suddenly brought to bear on the cooler pots, resulting in a short life for the pots. The temperature of the incoming air is not so constant as with the recuperative type of furnace; however, with proper control, these defects may be obviated to some extent. [Illustration: A MODERN GLASS HOUSE The Hermansen Continuous Recuperative Glass-melting Furnace in foreground (Twelve Covered Pot Type). ] By the kindness of Messrs. Hermansen, the patentees, I am permitted to illustrate their Recuperative Glass-melting Furnace, eight pot type. [Illustration: HERMANSEN GLASS HOUSE FURNACE (EIGHT POT TYPE) ] [Illustration: Sectional Elevation. A HERMANSEN’S CONTINUOUS RECUPERATIVE GLASS-MELTING FURNACE _P._ Producer. _B._ Burner. _G.P._ Glass Pocket. ] [Illustration: B HERMANSEN FURNACE Cross Section through Gas Producer. _P._ Gas Producer. _R._ Recuperators. ]