Refractories and Pots. With the introduction of more efficient pot furnaces and tanks in which higher temperatures were reached {t soon became evident that the question of refractories would have to be investigated in order that the pots, tank blocks and furnace parts, would stand up to the increased strain which was being put upon them. During the war a large amount of experimental and practical work was undertaken with a view to improvement in this direction. As a result of some of these investigations a provisional specification was drawn up for the help of users and makers of refractories, and it was hoped by this means to standardize the types of clay, percentage and size of grog, porosity, shrinkage and other factors necessary in production of the refractory articles used.
Evidence would appear to point to the fact that in so far as con- cerns the majority of types of optical glass, and, if it were an econom- ical proposition, for other glasses also, pots of a porcelain nature or of a composition approximating in relative proportions of alumina and silica to kaolinite have given the most satisfactory results. In connexion with the manufacture of optical glass in America for war purposes it was found as a result of considerable experiment that a pot of the porcelain type was the best suited to their purpose. In other directions considerable experimental work has been devoted to the production of pots by the ordinary casting and by the vacuum casting processes, and also of pots from osmose clay. In each case results of great promise have been obtained.
Furnaces. There is no doubt that the exigencies of the war in relation to glass production caused British manufacturers to con- sider very seriously the equipment at their command in respect of its efficiency and quality of output. Although in some instances a reasonably efficient type of furnace had been installed, the general run of furnaces, although satisfying the type of work performed in Great Britain before the war, were unable to attain' or maintain the necessary temperatures for producing certain essential kinds of glass for the supply of which the British consumer had previously relied on foreign sources. In factories existing at the outbreak of war the more efficient furnaces were of the regenerative type, but in the recently erected pot furnaces the tendency has been to adopt the recuperative principle. In this type of furnace there are two sets of channels or passages, one for the air supply and the other to carry away the hot products of combustion; the temperature of the air is raised due to interchange of heat by conduction through the common party wall of the channels. As the flow of the secondary air and hot flue gases are constant in direction, there are, therefore, no reversing valves to be operated as is the case in the regenerative type, and it is claimed that the furnace can be maintained at a more even temperature in the former than in the latter.
The recuperative type of furnace is producer-gas-fired. The furnaces, according to the designer, differ in respect of the disposition of their elements; in one type both the producer and recuperators are situated immediately below the furnace, and both the air pas- sages and hot flue gas passages are disposed horizontally, whereas in another type the recuperators are at the sides, and the air passages are vertical whilst the flue gas passages are horizontal. It is claimed for the latter type that glass from a broken pot can be more easily dealt with and is not likely to cause so much damage.
Oil Fired Furnaces. Oil firing has not been installed to any extent in the glass industry in England and in very few, if any, cases has the furnace been designed specifically for oil fuel. But the coal strike in 1921 and consequent high price and irregular supplies of
coal caused attention to be more particularly directed to oil as a fuel, and during the first half of 1921 some optical glass furnaces in England were fired with heavy oil.
From experience gained so far it would appear that better results were obtained with the heavier grades of oil, and that tank furnaces lend themselves more readily to this type of fuel. In the case of pot furnaces the objection is raised that the pots are liable to suffer on account of the irregular heating due to localized combustion.
The prospect of increased consumption of oil as fuel has led naturally to efforts being made to improve the existing types of oil burners in the direction of better efficiency, etc. Several oil burners are now on the market, in some of which atomization is effected by steam under pressure. In others mechanical means and air pressure are utilized. Although more complete atomization is obtained by the former means, yet it appears to be generally admitted that the burner utilizing air pressure with some mechanical means for assist- ing atomization gives more complete combustion and higher tem- peratures. The virtue in this method of firing is increased cleanliness and the absence of discolouration or deterioration of the glass, due to the effects of the flame coming into contact with it. Moreover, with oil fuel the temperatures can be more easily controlled.
Annealing. Prior to the war a very wide gulf separated the methods in use for annealing optical glass from those practised by the makers of other types of glassware. In the former an efficient system of well-lagged electrically heated towers ensured a satis- factory result. In the latter, however, a primitive, straight-through tunnel (usually coke heated) formed the lehr. It was open to the objection that it was exceedingly draughty and the glass was hurried through in all too short a time. During the war, however, when new types of ware had to be produced in which the annealing needed to be above suspicion, close attention was devoted to the subject, of improved lehrs. In many of the factories considerable care was ex- ercised to ensure efficiency in this operation. The site was well chosen, the system of heating was considered in relation to the necessity of a variation in the maximum temperature according to the class of ware being annealed, and of a gradual fall in tempera- ture after passing the hottest zone. Precautions were taken to pre- vent draughts sweeping through the lehr and so defeating the object of the operation. (H. JN.; S. W. M.)
"GOEBEN" AND "BRESLAU." The '"Goeben' and 'Breslau' incident " forms an interesting part of the naval history of the World War, since the escape of the German battle-cruiser " Goeben " from Messina on Aug. 6 1914 enabled it to proceed to Constantinople and to exercise a powerful influence on Turkey and the outcome of the war.
When the war broke out the British forces in the Mediter- ranean under the commander-in-chief Vice-Adml. Sir A. Berkeley Milne consisted of three battle-cruisers: the " Inflex- ible " (flag.), "Indomitable" and "Indefatigable" (each eight i2-in. guns, 23 knots); the ist Cruiser Squadron (under Rear-Adml. E. C. Troubridge): "Defence" (four 9-2-in., ten 7-S-in.), "Black Prince," "Duke of Edinburgh," "Warrior" (each six 9-2-in., ten 6-in.); the four light cruisers, " Chatham," " Dublin," " Gloucester," " Weymouth," and the sth De-
SARDINIA
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INFLEXIBLE
INDOMITABLE
INDEFATIGABLE
TROUBRIDGE
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DEFENCE WARRIOR BLACK PRINCE DUKE OF EDINBURGH
GOEBEN & BRESLAU 6.10p.m.
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.-> DUBLIN t.10 p.m.
GOEBEN & BRESLAU
Aug 6-h 6.10p.m.
