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oped during drying and will form a light protective coating for the wall. The boiler is then ready for use. Fig. 1 shows a section of a furnace wall made of excellent brick, care- fully made up, that has successfully withstood high rates of firing in an oil fired furnace. This wall en- countered temperatures up to 3000 degrees Fahr. and appears to be in as good condition as when originally layed. Marine boilers should use only the best quality of fire clay brick of which there are many on the market. The composition will vary within wide margins, but in general, it is composed of approximately 50 per cent silica, 40-45 per cent alumina, 2 per cent iron oxide, and the re- mainder titanium, magnesium, cal- cium, and other oxides in small amounts. The relative values of a hand made brick versus a machine made brick is a debatable question. In each case certain advantages are claimed; a hand made brick is be- lieved to be more homogeneous, whereas a machine made brick should be more even in its dimen- sions. All brick during manufac- ture must be well burned in order to develop strength and a finely — grained structure. The brick as re- ceived must be free of cracks, and voids, and the corners must be suf- ficiently strong to resist crumbling in handling. In service a fire brick is subjected to certain conditions which tend to shorten the life of the brick and cause failure regardless of the care used in installing. The most impor- tant characteristics which a fire clay brick must possess are: | Under higherates of steaming fur- nace temperatures as high as 3000 degrees may occur. The brick must be able to withstand these high tem- peratures without softening or fus- ing. Fig. 2 shows a wall made up of brick, satisfactory in all respects, shrinkage, cracking, spalling, etc., except resistance to fusion. This wall was as carefully made up as the wall shown in Fig. 1. Near the top right side, tears of melted brick are beginning to form, while on the left side the wall has completely fused. Lack of resistance to fusion may be due to a number of closely allied causes; the manufacturing processes; the mixture of the clay; the composition of the original clay; fluxes in the clay; the atmosphere within the furnace; impurities in the brick; and other reasons. Any or all of these characteristics may cause the brick to fail. The entire failure of a brick wall by bulging and subsequent collapse may be due to excessive expansive characteristics of the brick. A fire clay refractory brick is the result of a compromise between clays of dif- ferent analyses; the two necessary ingredients common to all suitable fire clay materials being silica and alumina. These are found in vari- ous proportions in clay deposits in different sections of the country. They are analysed and mixed in an endeavor to obtain the proportions which have been found most desir- able, namely, 50 per cent silica and 40-45 per cent alumina. Generally speaking, alumina in a fire clay brick causes contraction, whereas Silica causes expansion. In a wel] propor- tioned brick these factors balane each other and the changes in se ume during use are corresponding] small. When improper proportions are used, shrinkage of the brick is liable to occur. A furnace wall made of brick hay- ing poor resistance to shrinkage takes the appearance of the section of wall shown in Fig. 3. This par- ticular brick was satisfactory in re- gard to grain structure, strength and had excellent resistances to tu- sion, but the excessive shrinkage showed it to be undesirable for ma- rine purposes. When shrinkage oc- curs to a lesser extent than is shown in this illustration, small surface cracks may develop. In either ease the result is harmful to the boiler lining, the strength of the wall is re- duced; insulation is destroyed; and, as it admits air into the furnace it results in decreased boiler economy. (To be Continued) Annual Dinner of Schools The annual dinner for the Cleve- land navigation and _ engineering schools of the Lake Carriers’ associa- tion, was held at Hotel Hollenden, Cleveland, on Feb. 11. George A. Marr, vice president of the associa- tion, presided as toastmaster. Of the 61 students enrolled in the naviga- tion school, 32 were seeking original licenses and 29 a raise in grade, and in the engineering school 25 were working for original licenses and 21 for raise in grade. Extending Dry Dock at Bremen to Over 1000 Feet 22 MARINE REVIEwW—March, 1931 HE great harbor at Bre- men, Germany, is a scene of bustling activity these days for work is_ being pushed on the Kaiserdock II, which is being extended to a length of 335 meters or more than 1000 feet: This added length will make it the greatest dry dock in all of Europe and will enable it to accommodate vessels up to 75,000 British registered tons. The greatest German vessels are the BREMEN and Europa of about 50,- 000 British registered tons. ASE