Carlsruhe, Freiburg, Pforzheim, and Heidelberg. There were in 1900 fourteen cities of upward of 10,000 population. The State includes a thickly settled portion of the Rhine Valley about 160 miles long, with an average width of 10 miles, which would seem to be a specially good field for electric railway lines. And yet at present electric lines are in operation only in or near the following cities: Mannheim (including Ludwigshafen extension)......... Length of line. ..miles... 25 ..do...... 9 ..do...... 111⁄2 ..do...... 8 In each case the same track is used in part by the cars of several lines. Thus the total track length of the Mannheim city and suburban lines is 14 miles. The city of Kehl, Baden, is connected with Strassburg by a branch of the Strassburg city lines, but does not operate an independent line. Of the above lines, each belongs to the respective city except in the case of the Heidelberg city lines, which are operated by a private corporation, the city being the owner of three-fourths of the capital stock. The fare charged varies with the distance, long rides and transfers on a single fare not being permitted to the extent they are in the United States. The fare for ordinary distances is 10 pfennigs (22) cents), tickets good for 25 rides being sold for 2 marks (48 cents). Of the lines now in operation in Baden only two can be said to be interurban lines-a line of about 9 miles from Heidelberg to Wiesloch and a somewhat shorter line from Carlsruhe to Durlach. H. W. HARRIS, Consul. MANNHEIM, GERMANY, August 14, 1903. CONGRESS OF GERMAN ELECTRICIANS. (From United States Consul Harris, Mannheim, Germany.) Beginning with June 7, 1903, a three days' congress of the German Society of Electricians was held in Mannheim. The meetings were attended by about 300 electrical engineers from all parts of the Empire. Papers were read on a variety of topics pertaining to electrical engineering, especially as applied to street-railway construction, electric lighting, etc. Among those who presented papers were Privy Councilor Professor Arnold, of Carlsruhe; Professor Görges, of Dresden; and Baron von Gaisberg, of Hamburg. At this meeting, as at similar meetings in Germany, that which first attracts the attention of the observer is the active part taken by No 278-03-6 teachers from the technical and other schools in what might be regarded the purely practical side of the subject. Thus, in this particular case the discussions led into the construction of street railways, installation of light and power plants, etc. Among those who took a leading part in these discussions were teachers and professional men. No opinion is ventured as to whether, upon the whole, a science such as that of electricity, mining, architecture, etc., progresses more rapidly if left mainly to what may be termed the self-made unprofessional engineer or if left more under professional or academic control. The German manufacturer or railway builder would doubtless answer the question in favor of the professionally trained expert. The conditions existing in the two countries being in many respects different, the advancement made in electrical engineering, for example, afford no complete answer to the question. It would be conceded on both sides of the ocean that in the more difficult field of chemical manufacture the professionally trained chemist has been indispensable. MANNHEIM, GERMANY, August 4, 1903. H. W. HARRIS, Consul. CALCAREOUS BRICK AND STONE MANUFACTURE IN GERMANY. (From United States Consul-General Mason, Berlin, Germany.) During the past year frequent inquiries have been received at this consulate from correspondents in the United States desiring detailed and precise information concerning the manufacture and use in Germany, for building purposes, of calcareous brick and stone made by artificially combining under pressure sand with slacked or unslacked lime. The range of these inquiries has been principally as to the length of time that such building materials. have been made and used in this country, whether they have stood the test of varying temperature in wet or specially exposed situations and under heavy crushing strain, what the Government architects and leading builders think of them, and especially what patented machinery and methods for making such materials are most highly esteemed and approved in this country. The latter class of interrogatories has been stimulated by the fact that certain patented machines and processes of German origin for making sandlime brick have been recently exploited in the United States, one of which at least has been advertised there as having been "adopted by the German Government." With a view of answering as far as practicable these inquiries, the following report is respectfully submitted. FIRST EXPERIMENTS IN MANUFACTURE. The first experiments in making bricks from sand and lime appear to have been undertaken at Potsdam about thirty years ago. They were suggested by the fact that Potsdam, like many other places in central Germany, is surrounded by a wide, sandy plain, which furnishes neither clay for bricks nor stone for building purposes. These calcareous bricks were first hardened by exposure to the air, a tedious process which required several months, although the bricks hardened in that way seem to have stood all tests and continue to harden with increasing age. About 1880 the discovery was made that the freshly pressed bricks of sand and lime could be hardened in a few hours by heat and pressure of steam, and from that date the manufacture developed into an industry which reached its maturity in Germany tour. or five years ago. Plants on a large scale were first constructed in this country, and the industry has gradually extended throughout the Continent and to Great Britain. ESSENTIAL CONDITIONS OF THE PROCESS. The indispensable materials are good, clean, sharp sand—as free as possible from impurities and containing not less than 70 per cent of silicic acid-and fresh quicklime, such as would be suitable for making mortar of good quality. All the different methods or "systems" thus far invented for combining these two materials. may be grouped in two categories, viz, those in which the lime is. slacked separately and then mixed with sand and, secondly, those in which the dry sand and quicklime are thoroughly mixed and then slacked. The latter method is generally practiced, for reasons that will be hereinafter stated. Throughout the whole process, whichever method of slacking is used, the point of prime importance is uniformity, without which there can be no excellence in the product. nor profit in the manufacture. The best results require the following conditions to be fulfilled: 1. Uniformity in the grain and purity of the sand employed. If part of the sand is fine and part coarse, or if there is a mixture of dirt or any impurity in it, the quality of the brick or stone produced will be affected in proportion to the degree of such defect in the crude material. 2. Uniformity in chemical composition and the consequent chemical action of the lime on the sand. By this is meant that the lime used must be fresh and quick throughout and not partially slacked on the exterior of the mass by exposure to moisture or weather. 3. Uniformity in the proportion of lime to sand throughout the mixture. It will not do to have one part of the mixed material rich in lime while another is poor; the two substances (sand and lime) must be so thoroughly mingled that the mixture is of homogeneous composition throughout. 4. The slacking process, whether done before or after the lime is mingled with the sand, must be thoroughly and uniformly accomplished, so that the whole of the lime shall be converted into hydrate of calcium and no dry, unslacked pellicles left in the mortar when it goes to the press. 5. Uniformity in the proportion of water in the mortar, so that each part of the mixture shall be equally wet and fluid. For this purpose very thorough mixing and stirring, with machinery specially devised for the purpose, is necessary to secure complete combination between the elements and a smooth, uniform consistency in the plastic state. Only when all these fundamental conditions are observed will the sand brick or stone be uniform and satisfactory in its durability, in its resistance to moisture, frost, and pressure, and in its consequent value as building material. PROCESS OF MANUFACTURE. As to materials, the lime, which should first be pulverized in a ball or other mill, should be so pure that when slacked it will contain not less than 92 per cent of oxide of calcium. Any admixture of clay or magnesia is detrimental, and if such admixture exceeds even a small percentage the lime is thereby rendered unfit for the calcareous-sandstone process. Fresh, dry quicklime is slacked by absorbing 32 parts of water to 100 of lime. The union of the elements is at first mechanical, but it develops heat and under this higher temperature a chemical combination occurs, producing hydrate of lime or hydroxide of calcium, which is considerably larger in bulk than the unslacked lime from which it was produced. For the reason that the heat engendered by the slacking process promotes the chemical union between the lime and sand and further increases its plasticity, whereby it works smoothly and easily in the press, the best practice favors the mixing of the dry sand and lime before the slacking process takes place. So important is the element of heat in this connection that some mixing machines are provided with steam jackets in which exhaust steam from the engine is used to maintain a uniformly high temperture. From the mixing machine the mortar passes to the machine press, of which there are several types manufactured by German makers of established reputation, viz: Amandus Kahl, of Hamburg; Messrs. Brück, Kretschel & Co., of Osnabrück; Messrs. Röhrig & Koenig, of Magdeburg-Ludenberg; Friedrich Krupp Grusonwerk, of Magdeburg-Buckau; F. Komnick, at Elbing; and several others. Whatever the type, the press must be constructed to receive the mortar in molds which are automatically filled and the material pushed home by plungers which, as the machine revolves, exert an enormous pressure- -as high as 350,000 pounds to each brickwhich renders it dense, firm, and smooth. In this condition they are discharged from the press, loaded upon small platform cars, and run into the hardening boiler. The hardening boiler is a long cylinder of boiler iron, 8 or 9 feet in diameter, with a rail track laid along the bottom to receive the cars, and a lid or door which swings on hinges and covers the entire end of the cylinder. When the boiler is filled with cars on which the freshly molded bricks are piled in loose, open formation, this door, or man-head, is closed, secured with bolts, and steam turned in. In the beginning of the industry, offsteam with a low degree of pressure was used, but experience showed that, other things being equal, the hardness of the bricks is increased with the degree of steam pressure applied, so that the best practice now favors a pressure of 9 atmospheres (132 pounds per square inch) for small factories and 10 atmospheres (147 pounds) for large plants where every step of the process is on an extensive scale. The duration of a "turn"-that is, the filling of a boiler, the hardening, cooling, and discharge of the finished contents-occupies from ten to fifteen hours, and the bricks, as soon as they are cool, are ready for use. They can be made of any size or form, but are usually of the ordinary type, 9 inches long by 41⁄2 inches broad and 234 inches thick, and as in the best presses the enormous strain is applied vertically—that is, upon the top and bottom of the brick-it is prepared to sustain a heavy crushing strain when laid in a wall. PRESENT STATUS AS BUILDING MATERIAL. Inevitably the record of sand-lime brick as constructive material. is brief and recent. There are probably not 100 of them in any wall in this country more than thirty years old. Their durability for long periods, upon which their real value as building material mainly depends, has been theorectically demonstrated by various and thorough scientific tests, based on what had been previously known concerning the permanence of sand when chemically and mechanically combined with lime. It has been stated in this report that the earliest calcareous-sand bricks were slowly hardened by exposure to the air, and that they have continued to grow firmer and more flinty with increasing age. Elaborate tests have been since made with both air-dried and steam-hardened bricks and building stones by the |