It follows from these considerations that, although the recuperative furnace is somewhat simpler and cheaper to construct, it requires, if anything, more careful maintenance than the older forms of regenerative furnace. Tank furnaces for the production of sheet-glass in this country are generally worked from early on Monday morning until late on Saturday night, glass-blowing operations being suspended during Sunday, although the heat of the furnace must be maintained. On the Continent, and especially in Belgium, the work in connection with these furnaces goes on without any intermission on Sunday--a difference which, however desirable the English practice may be, has the effect of handicapping the output of a British furnace of equal capacity by about 10 per cent. without materially lessening the working cost. The process of blowing sheet-glass in an English glassworks is generally carried out by groups of three workmen, viz., a “pipe-warmer,” a “gatherer” and a “blower,” although the precise division of the work varies according to circumstances. The pipe-warmer’s work consists in the first place in fetching the blowing-pipe from a small subsidiary furnace in which he has previously placed it for the purpose of warming up the thick “nose” end upon which the glass is subsequently gathered. The sheet-blower’s pipe itself is an iron tube about 4 ft. 6 in. long, provided at the one end with a wooden sleeve or handle, and a mouthpiece, while the other end is thickened up into a substantial cone, having a round end. Before introducing the pipe into the opening of the tank furnace, the pipe-warmer must see that the hot end of the pipe is free from scale or dirt and must test, by blowing through it, whether the pipe is free from internal obstructions. He then places the butt of the pipe in the opening of the furnace and allows it to acquire as nearly as possible the temperature of the molten glass. When this is the case the pipe is either handed on to the gatherer, or the pipe-warmer, who is usually only a youth, may take the process one step further before handing it on to the more highly skilled workman. This next step consists in taking up the first gathering of glass on the pipe. For this purpose the hot nose of the pipe is dipped into the molten glass, turned slowly round once or twice and then removed, the thread of viscous glass that comes up with the pipe being cut off against the fire-clay ring that floats in the glass in front of the working opening. A small quantity of glass is thus left adhering to the nose of the pipe, and this is now allowed to cool down until it is fairly stiff, the whole pipe being meanwhile rotated so as to keep this first gathering nicely rounded, while a slight application of air-pressure, by blowing down the pipe, forms a very small hollow space in the mass of glass and secures the freedom of the opening of the pipe. When the glass forming the first