Great as have been the improvements in all kinds of domestic heating apparatus, we all know that a very large proportion of the available heat still eludes us and passes through chimneys to the open air. And there is no doubt Steam Boiler Incrustations, According to the Chemical News, M. E. Wiederhold states that the hardest incrustlttions of this kind are formed when the quantity of carbonate of lime amounts to from 20 to 25 per cent of the entire mass. He has found, by an experience extending over several years, that some kinds of clay, among these the substance known as kieselschiefer (a peculiarly fatty clay), when suspended in the water, contained in steam boilers, prevent the particles of carbonate and sulphate of lim9 dissolved in the water, even ifthe latter is very hard, to cling together, and become fixed to the sides of the boilers, forming there a hard incrustation. A series of experiments, made on purpose, and continued for a sufficient length of time to yield a reliable result, has fully proved that the addition to the feed-water of the steam boilers of fatty clays, especially the kind known as fuller's earth, entirely prevents boiler incrustations, even where, of necessity, very hard water has to be used as feed water. A. loose, soft mud is deposited as soon as the liiotion of the water, due to the bojlinq, cellBcs on cool. also that much of the combustible matter is distilled rather than burned, and passes off as gas, not only failing to give its share of heat but taking with it a portion of the heat furnished by that which is consumed. Our engravings exhibit a form of grate called by the inventor a Perfect Combustion Grate, calculated to obviate these losses, by securing more perfect combustion, and using to greater advantage the heat produced. To secure these ends the grate is constructed as shown in front elevation, Fig. 1, and in section, Fig, 2. It will be observed that tIm mason wo,'];: at the hack of Vm-. grata is Lurrnann's Blast Furnace. Engineering states that a considerable number of German ironmasters have, during the last two years, applied to their furnaces the system of Mr. Lurmann, the manager of the Georg-Marien Mining and Iron Company, of Osnabrtick, Prussia, the improvement consisting in closing the' front of the hearth, thereby dispensing with the dam stone, tymp, etc. A scoria outlet is set in the closed breast at a distance of about 6 in. below the tweers, and through this outlet the slag runs off regularly and constantly. The tapping hole is placed where the heat is greatest. This arrangement has been successfully worked for six months or more at the Old Park Iron Works, Shropshire, and more than one of our leading ironmasters have expressed their intention of adopting it. Its advantages are thus enumerated : 1.The slag discharges itself through the scoria outlet at about the same level, therefore there are no vacillations of the slag in the hearth, and the corroding of the wall is diminished. 2.As there is no fore-hearth, there are of course no repairs, and no breaking up of the scoria crust in the same. This is equal, as shown above, to a saving of at least twenty days per year. Suppose a large furnace produces forty tuns per day, the same will yield at least eight hundred tuns per year more, if built on Mr. Liirmann's principle than if it were of the ordinary construction. 3.As there are no interruptions, the furnace does not cool. It works more regular, as the heat in the furnace is always the same. 4.The dointg away with the dam and the fore-hearth allows the removal of the tapping- hole from the former into the wall of the hearth. The opening of the tapping-hole is then easy, as it is close to the greatest heat. 5.The completely-closed hearth allows a considerable increase of the pressure of the blast, because a throwing out of materials has become impossible. 6.The increase of the pressure is always of great importance, but especially where pit coal, anthracite, etc., are used; and where the layers are compact. The number of charges can be greater, effecting a corresponding increase of produce. 7.The augmentation in the number of tweers, and the equal distribution of them, made feasible by the doing away with the forepart of the hearth, allow a better and equal distribution of the blast in the hearth; the furnace therefore works better, and a greater quantity of ore is smelted, provided there is sufficient blast. 8.The number of hands may be lessened, as the operations are few and easy; the same need not be of great skill and experience. No fire clay and other refractory materials for the repairs, and less tools,are wanted. It may be mentioned that formerly the smelters of Georg-Marien-Hutte, when working, were almost stripped ; now they are always in full working dress. To Clean OiLCLOTH.—An oilcloth should never be scrubbed with a brush, but, after being first swept, should be cleaned by washing with a soft flannel and lukewarm or cold water. On no account use soap or water that is hot, as either would have a bad effect on the paint. When the oilcloth is dry, rub it well with a small porticn of a mixture of bees' wax, softened with a minute quantity of turpentine, using for this purpose a soft furniture polishing brush. Oilcloth cared for in this way will last twice the time than with ordinary treatment.-Sptm'MS Piesse. We have received a number of communications on the subject of street crossings, none of which seem to us to contain any practicable suggestions, they are therefore declined with thanks. October 1869.] factttific Jitumem MUNN&COMPANY, Editors and Proprietors. PUBLISHED WEEKLY AT NO. 37 PARK ROW (PARK BUILDING), NEW YORK O. D. MDSS, S. II. WALES, A. E. BEACH. ” The American News Company,” Agents.121 Nassau street.New yotk. The New York News Company,” 8 Spruce street. V OL. XXI., N o. 17 ... [NEw SERIES.]. .. Twenty-jowrtft Year. NEW YORK, SATURDAY, OCTOBER 23, 1869. Contents: (Illustrated articles are marked with an asterisk.) •Concrete Building-257Demuth's Improvement in Balloon Mailing'2571 Window Lights The Influence of Weather on Sickness 258 Retarding the Growth of Strawberry Vine s25S Cement258 JJon'l be Afraid to Advertise258 •Foster's India - Rubber Decoy Duck260 Applications of Photography to Astronomy259 Wasteful Mining in California259 Teleiconograptie259 Difficulties to be Surmounted in Working the Suez Canal260 •The Peach Tree Insect280 wfhe Welcome Stranger” Nugget Found near Dunolly, in Australia 260 The Holstein Intermarime Canal. .',60 •The Contraction or Shrinking of Timber. 261 On Cotton Seed Oil, and its Defection when Mixed with other Glass ,.263 Fresh Water at'the Seaside263 Glass Manufature in the United States263 Testing Boilers263 improvement In Farm Gates.....264 Suspension Bri dges26-1 Steam Boiler Incrustations264 Increase of Weight During Combustion264 Improve™ ent in O pen Fire Grate.264 Lurmann's Blast Furnace264 Facts about the C'roton Water Supply265 Circular Motion and Rectilinear Motion265 The ExhibitJonof the American Institute 2G5 InterestingPatent Decision—When Does an English Patent take Date ?266 Osborn's New Treatise on the Metallurgy of Iron and Steel..267 Steam Power on Canals267 Oils The Manufacture of Sulphuric Acid262 The Relation of Mechanism to Art.262 The California Fairs262 On the Assimilation of Inorganic Substances in the Animal orny263 Tyndail's Theory of Comets263 How to Kill tlie Fleas and the Dog263 261 Dredging ill the Gulf Stream267 Inventions Patented ill England by Americans268 New Publications268 Manufacturing, Mining, and Railroad Items2 68 Hecent American and Foreign Patents26B Answers to Correspondents269 List of Patents'269 Patent Decision270